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NASA’s Curiosity rover finds clues to how water helped shape Martian landscape

This series of images reconstructs the geology of the region around Mars’ Mount Sharp, where NASA’s Curiosity Mars rover landed and is now driving. Credit: NASA/JPL-Caltech

Observations by NASA’s Curiosity Rover indicate Mars’ Mount Sharp was built by sediments deposited in a large lake bed over tens of millions of years

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This interpretation of Curiosity’s finds in Gale Crater suggests ancient Mars maintained a climate that could have produced long-lasting lakes at many locations on the Red Planet.
“If our hypothesis for Mount Sharp holds up, it challenges the notion that warm and wet conditions were transient, local, or only underground on Mars,” said Ashwin Vasavada, Curiosity deputy project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California. “A more radical explanation is that Mars’ ancient, thicker atmosphere raised temperatures above freezing globally, but so far we don’t know how the atmosphere did that.”

Why this layered mountain sits in a crater has been a challenging question for researchers. Mount Sharp stands about 3 miles (5 kilometers) tall, its lower flanks exposing hundreds of rock layers. The rock layers — alternating between lake, river and wind deposits — bear witness to the repeated filling and evaporation of a Martian lake much larger and longer-lasting than any previously examined close-up.

“We are making headway in solving the mystery of Mount Sharp,” said Curiosity Project Scientist John Grotzinger of the California Institute of Technology in Pasadena. “Where there’s now a mountain, there may have once been a series of lakes.”

Curiosity currently is investigating the lowest sedimentary layers of Mount Sharp, a section of rock 500 feet (150 meters) high, dubbed the Murray formation. Rivers carried sand and silt to the lake, depositing the sediments at the mouth of the river to form deltas similar to those found at river mouths on Earth. This cycle occurred over and over again.

“The great thing about a lake that occurs repeatedly, over and over, is that each time it comes back it is another experiment to tell you how the environment works,” Grotzinger said. “As Curiosity climbs higher on Mount Sharp, we will have a series of experiments to show patterns in how the atmosphere and the water and the sediments interact. We may see how the chemistry changed in the lakes over time. This is a hypothesis supported by what we have observed so far, providing a framework for testing in the coming year.”

After the crater filled to a height of at least a few hundred yards, or meters, and the sediments hardened into rock, the accumulated layers of sediment were sculpted over time into a mountainous shape by wind erosion that carved away the material between the crater perimeter and what is now the edge of the mountain.

On the 5-mile (8-kilometer) journey from Curiosity’s 2012 landing site to its current work site at the base of Mount Sharp, the rover uncovered clues about the changing shape of the crater floor during the era of lakes.

“We found sedimentary rocks suggestive of small, ancient deltas stacked on top of one another,” said Curiosity science team member Sanjeev Gupta of Imperial College in London. “Curiosity crossed a boundary from an environment dominated by rivers to an environment dominated by lakes.”

Despite earlier evidence from several Mars missions that pointed to wet environments on ancient Mars, modeling of the ancient climate has yet to identify the conditions that could have produced long periods warm enough for stable water on the surface.

NASA’s Mars Science Laboratory Project uses Curiosity to assess ancient, potentially habitable environments and the significant changes the Martian environment has experienced over millions of years. This project is one element of NASA’s ongoing Mars research and preparation for a human mission to the planet in the 2030s.

“Knowledge we’re gaining about Mars’ environmental evolution by deciphering how Mount Sharp formed will also help guide plans for future missions to seek signs of Martian life,” said Michael Meyer, lead scientist for NASA’s Mars Exploration Program at the agency’s headquarters in Washington.

JPL, managed by Caltech, built the rover and manages the project for NASA’s Science Mission Directorate in Washington.

For more information about Curiosity, visit: http://www.nasa.gov/msl and http://mars.jpl.nasa.gov/msl/

Note : The above story is based on materials provided by NASA/Jet Propulsion Laboratory.

The first X-ray diffraction measurements on Mars

In 2012 the Mars Science Laboratory landed in the fascinating Gale crater. The Gale crater is of such great interest because of the 5.5 km high mountain of layered materials in the middle. This material tells an intricate story of the history of Mars, perhaps spanning much of the existence of this mysterious planet.

Once positioned, the Curiosity rover began field studies on its drive toward Aeolis Mons (also unofficially known as Mount Sharp), the central peak within the crater. Curiosity has travelled more than 9.4 km so far and during its trip up the mountain, Curiosity has begun taking samples of the mountain’s lower slopes.

CheMin is one of ten instruments on or inside Curiosity, all designed to provide detailed information on the rocks, soils and atmosphere.

CheMin is actually a miniaturised X-ray diffraction/X-ray fluorescence (XRD/XRF) instrument, approximately the size of a shoebox, that uses transmission geometry with an energy-discriminating CCD detector to obtain unparalleled results in quite challenging conditions.

Five samples have been analysed by CheMin so far, namely a soil sample, three samples drilled from mudstones and a sample drilled from a sandstone. Rietveld and full-pattern analysis of the XRD data have revealed a complex mineralogy, with contributions from parent igneous rocks, amorphous components and several minerals relating to aqueous alteration, for example clay minerals and hydrated sulphates. In addition to quantitative mineralogy, Rietveld refinements also provide unit-cell parameters for the major phases, which can be used to infer the chemical compositions of individual minerals and, by difference, the composition of the amorphous component. Coincidentally CheMin’s first XRD analysis on Mars coincided with the 100th anniversary of the discovery of XRD by von Laue.

So far CheMin has returned excellent diffraction data comparable in many respects with data available on[powder diffraction pattern from Martian soil] Earth. It has managed this even though several aspects of the instrument, particularly its small size limit the quality of the XRD data. These limitations could, however, be improved through modification of the instrument geometry. One of the most significant issues limiting remote operation is the requirement for powder XRD of a finely powdered sample. CheMin largely surmounts this difficulty through the use of its unique sample vibration device.

Data obtained so far has already provided new insights into processes on Mars, and the instrument promises to return data that will answer numerous questions and shed further light on the history of the Gale crater.

Work is already progressing in developing an upgraded instrument with changes in the reflection geometry. Coupled with data-processing software interface advances, we may see future improvements to non-contact diffraction analysis of the surfaces of planetary bodies.

A video of Professor David L. Bish presenting work from the Mars science mission :

The lecture was part of a series of talks organised by the University of Liverpool as part of their Science & Society Lecture Series.

Reference :
Bish et al. (2014). IUCrJ, 1, 514-522; doi:10.1107/S2052252514021150

Note : The above story is based on materials provided by International Union of Crystallography.

Saturn’s largest moon is a windy place

Cassini radar sees sand dunes on Saturn’s giant moon Titan (upper photo) that are sculpted like Namibian sand dunes on Earth (lower photo). The bright features in the upper radar photo are not clouds but topographic features among the dunes. Credit: NASA

Titan, Saturn’s largest moon, is a peculiar place. Unlike any other moon, it has a dense atmosphere. It has rivers and lakes made up of components of natural gas, such as ethane and methane. It also has windswept dunes that are hundreds of yards high, more than a mile wide and hundreds of miles long — despite data suggesting the body to have only light breezes.
Research led by Devon Burr, an associate professor in Earth and Planetary Sciences Department at the University of Tennessee, Knoxville, shows that winds on Titan must blow faster than previously thought to move sand. The discovery may explain how the dunes were formed.

The findings are published in the current edition of the academic journal Nature.

A decade ago, Burr and other scientists were amazed by the Cassini spacecraft’s pictures of Titan that showed never-before-seen dunes created by particles not previously known to have existed.

“It was surprising that Titan had particles the size of grains of sand — we still don’t understand their source — and that it had winds strong enough to move them,” said Burr. “Before seeing the images, we thought the winds were likely too light to accomplish this movement.”

The biggest mystery, however, was the shape of the dunes. The Cassini data showed that the predominant winds that shaped the dunes blew from east to west. However, the streamlined appearance of the dunes around obstacles like mountains and craters indicated they were created by winds moving in exactly the opposite direction.

To get to the bottom of this conundrum, Burr dedicated six years to refurbishing a defunct NASA high-pressure wind tunnel to recreate Titan’s surface conditions. She and her team then turned up the tunnel’s pressure to simulate Titan’s dense atmosphere, turned on the wind tunnel fan, and studied how the experimental sand behaved. Because of uncertainties in the properties of sand on Titan, they used 23 different varieties of sand in the wind tunnel to capture the possible sand behavior on Titan.

After two years of many models and recalibrations, the team discovered that the minimum wind on Titan has to be about 50 percent faster than previously thought to move the sand.

“Our models started with previous wind speed models but we had to keep tweaking them to match the wind tunnel data,” said Burr. “We discovered that movement of sand on Titan’s surface needed a wind speed that was higher than what previous models suggested.”

The reason for the needed tweaking was the dense atmosphere. So this finding also validates the use of the older models for bodies with thin atmospheres, like comets and asteroids.

The discovery of the higher threshold wind offers an explanation for the shape of the dunes, too.

“If the predominant winds are light and blow east to west, then they are not strong enough to move sand,” said Burr. “But a rare event may cause the winds to reverse momentarily and strengthen.”

According to atmospheric models, the wind reverses twice during a Saturn year which is equal to about 30 Earth years. This reversal happens when the sun crosses over the equator, causing the atmosphere — and subsequently the winds — to shift. Burr theorizes that it is only during this brief time of fast winds blowing from the west that the dunes are shaped.

“The high wind speed might have gone undetected by Cassini because it happens so infrequently.”

This research was supported by grants from NASA’s Planetary Geology and Geophysics Program and the Outer Planets Research Program. A new grant will allow Burr and her colleagues to examine Titan’s winds during different climates on Titan as well as the effect of electrostatic forces on the sand movement.

Burr’s team included UT Earth and Planetary Sciences Assistant Professor Josh Emery as well as colleagues from the Johns Hopkins University Applied Physics Laboratory, SETI Institute, Arizona State University, and the University of California, Davis.

Reference:
Devon M. Burr, Nathan T. Bridges, John R. Marshall, James K. Smith, Bruce R. White, Joshua P. Emery. Higher-than-predicted saltation threshold wind speeds on Titan. Nature, 2014; DOI: 10.1038/nature14088

Note : The above story is based on materials provided by University of Tennessee.

Rare insect found only in glacier national park imperiled by melting glaciers

A spring fed stream in the Two-Medicine drainage of Glacier National Park is one of 2 new locations for the western glacier stonefly (Zapada glacier). Credit: United States Geological Survey

The persistence of an already rare aquatic insect, the western glacier stonefly, is being imperiled by the loss of glaciers and increased stream temperatures due to climate warming in mountain ecosystems, according to a new study released in Freshwater Science.
In the study, scientists with the U.S. Geological Survey, Bucknell University, and the University of Montana illustrate the shrinking habitat of the western glacier stonefly (Zapada glacier) associated with glacial recession using data spanning from 1960 – 2012. The western glacier stonefly is only found in Glacier National Park and was first identified in streams there in 1963.

In a two year period beginning in 2011, scientists resampled six streams throughout the stonefly’s historical range and, using species identification and genetic analysis, found the western glacier stonefly in only one previously occupied stream and in two new locations at higher elevations.

For scientists, the concern is not just about this single species, since the stonefly is representative of an entire, unique ecosystem.

“Many aquatic species are considered vulnerable to climate change because they are cold water dependent and confined to mountaintop streams immediately below melting glaciers and permanent snowfields,” said Joe Giersch, project leader and USGS scientist. “Few studies have documented changes in distributions associated with temperature warming and glacial recession, and this is the first to do so for an aquatic species in the Rockies.”

The glaciers in Glacier National Park are predicted to disappear by 2030 and the western glacier stonefly is responding by retreating upstream in search of higher, cooler alpine stream habitats directly downstream of disappearing glaciers, permanent snowfields and springs in the park.

“Soon there will be nowhere left for the stonefly to go,” said Giersch.

USGS conducted this US FWS-funded research, in part, because the stonefly was petitioned for inclusion under the U.S. Endangered Species Act, and more information was needed on its status and distribution to make that determination.

“There are a handful of other coldwater dependent alpine aquatic species here in Glacier that are at risk of extinction due to the loss of permanent snow and ice. Under a warming climate, the biodiversity of unique aquatic alpine species – not just in Glacier, but worldwide – is threatened, and warrants further study,” said Giersch.

Results from the study will be featured in the upcoming issue of Freshwater Science.  The article is titled “Climate –induced range contraction of a rare alpine invertebrate”.

More information: www.jstor.org/discover/10.1086… 4&sid=21105382882073

Note : The above story is based on materials provided by United States Geological Survey.

Vilyuy River

This is a map of the Vilyuy River Watershed, based on USGS data.

The Vilyuy River is a river of the Central Siberian Plateau, longest tributary of the Lena River. About 2,650 kilometres (1,650 mi) long, it flows mostly within the Sakha Republic. Its basin covers about 491,000 square kilometres (190,000 sq mi).

The Vilyuy rises in the Evenky autonomous okrug and, flowing east, soon enters Sakha. It turns towards the south and southeast, then back towards the east, and finally enters the Lena about 350 kilometres (220 mi) downstream of Yakutsk, near Sangar. To the west of the Vilyui and Chona is the Nizhnyaya Tunguska River basin. The Vilyuy basin is sparsely populated. Small settlements along the river include Vilyuysk, Verkhnevilyuysk, Suntar, and Nyurba.

The river is first mentioned in the 17th century in connection with the Russian conquest of Siberia. In 1634, Russian Cossacks, headed by Voin Shakhov, established a winter settlement at the confluence of the Vilyuy and Tyuken Rivers. This settlement served as the administrative center of the area for several decades, after which it was moved to the Yolyonnyokh area 45 kilometers (28 mi) down by the Vilyuy River, where the ostrog (fortified settlement) of Olensk (now Vilyuysk) was founded in 1773.

In the 1950s, diamond deposits were discovered in the area, about 700 kilometres (430 mi) from its mouth. This led to the construction of the Mir Mine, together with access roads and an airport, and the Vilyuy Dam complex to generate power needed for the diamond concentrators.

 Note : The above story is based on materials provided by Wikipedia.

Geophysicists challenge traditional theory underlying the origin of mid-plate volcanoes

Traditional thought holds that hot updrafts from the Earth’s core cause volcanoes, but researchers say eruptions may stem from the asthenosphere, a layer closer to the surface. Credit: Virginia Tech

A long-held assumption about the Earth is discussed in today’s edition of Science, as Don L. Anderson, an emeritus professor with the Seismological Laboratory of the California Institute of Technology, and Scott King, a professor of geophysics in the College of Science at Virginia Tech, look at how a layer beneath the Earth’s crust may be responsible for volcanic eruptions.
The discovery challenges conventional thought that volcanoes are caused when plates that make up the planet’s crust shift and release heat.

Instead of coming from deep within the interior of the planet, the responsibility is closer to the surface, about 80 kilometers to 200 kilometers deep — a layer above the Earth’s mantle, known as the as the asthenosphere.

“For nearly 40 years there has been a debate over a theory that volcanic island chains, such as Hawaii, have been formed by the interaction between plates at the surface and plumes of hot material that rise from the core-mantle boundary nearly 1,800 miles below the Earth’s surface,” King said. “Our paper shows that a hot layer beneath the plates may explain the origin of mid-plate volcanoes without resorting to deep conduits from halfway to the center of the Earth.”

Traditionally, the asthenosphere has been viewed as a passive structure that separates the moving tectonic plates from the mantle.

As tectonic plates move several inches every year, the boundaries between the plates spawn most of the planet’s volcanoes and earthquakes.

“As the Earth cools, the tectonic plates sink and displace warmer material deep within the interior of the Earth,” explained King. “This material rises as two broad, passive updrafts that seismologists have long recognized in their imaging of the interior of the Earth.”

The work of Anderson and King, however, shows that the hot, weak region beneath the plates acts as a lubricating layer, preventing the plates from dragging the material below along with them as they move.

The researchers show this lubricating layer is also the hottest part of the mantle, so there is no need for heat to be carried up to explain mid-plate volcanoes.

“We’re taking the position that plate tectonics and mid-plate volcanoes are the natural results of processes in the plates and the layer beneath them,” King said.

Reference:
D. L. Anderson, S. D. King. Driving the Earth machine? Science, 2014; 346 (6214): 1184 DOI: 10.1126/science.1261831

Note : The above story is based on materials provided by Virginia Tech.

Early evolution of limb regeneration in tetrapods

Drawing (left) and photo (right) of some of the exemplar autopods displaying regeneration in Micromelerpeton. The normal condition is four digits in the hand with the phalangeal formula 2-2-3-3 and five digits in the foot with the phalangeal formula 2-2-3-4-3. (a) Right hand of specimen SSN 1102 showing enlarged metacarpal and proximal fusion of the first phalanges. (b) Left hand of specimen MB.Am. 1183 showing a fused metacarpal. (c) Left foot of specimen MB.Am. 1183 showing spur-like branching of the phalangeal element and an underdeveloped fibula (white arrow). (d) Left foot of specimen SSN GwK-34 showing a centrally positioned adventitious digit, note that both central digits are thinner than normal digits. Scale bar equals 1 mm.

Regeneration of missing body parts occurs in most animal phyla, whereas regenerative capabilities vary extensively even between closely related taxa . Much data have been gathered in recent years especially with a focus on the molecular and developmental mechanisms of regeneration and we may indeed be getting closer to a true understanding of its molecular basis .
By contrast, the evolution of regenerative capacity in animals and its ecological context has just recently shifted back into focus providing essential insights into the evolutionary history of regeneration . Thereby studies concentrated on extant animal regeneration models to investigate the distribution of regenerative capacities in a phylogenetic framework and to assess which factors may have played a role in the loss or maintenance of it, such as direct selection, pleiotropy or phylogenetic inertia .

Among tetrapods, salamanders display by far the highest regenerative capacity that includes the eyes, heart, tails and entire limbs . Therein, decades of research have been dedicated to the question of how it is possible for salamanders to repeatedly regenerate an entire limb in a matter of a few weeks and throughout their whole lifespan, while other tetrapods cannot .

The quest has undoubtedly been driven by the hope to eventually be able to induce human limbs to regenerate. Most studies investigating limb regeneration have focused on the Mexican axolotl Ambystoma mexicanum, but limb regeneration has been demonstrated in a number of additional salamander taxa, including those that undergo direct development .

One of the most striking steps in the regeneration cascade is the de-differentiation of cells that had a specific, differentiated identity prior to the injury taking place, which re-enter the cell cycle to form a growth zone, the blastema . The subsequent process of cell specification and pattern formation in the regenerating limb is not yet fully resolved. While grafting experiments and some molecular studies indicated that contrary to initial limb development, during regeneration the distal tip of the stump is specified first, followed by intercalary growth , more recent studies point towards a proximo-distal sequence of cell specification during regeneration, indicating that similar patterning modes may be used in development and regeneration . The high regenerative capabilities of salamanders have classically been regarded as exceptional among tetrapods . Among fish-like sarcopterygians (‘lobe-finned fish’), only lungfish are known to have a comparable capacity to regenerate their fore- and hind fins, including endoskeletal elements . Contrary to salamander limb regeneration, however, the morphological and molecular aspects of lungfish fin regeneration have not been addressed in detail yet, but it is known that after the initial healing of a wound a blastema forms, which is overall comparable to the blastema initiating salamander limb regeneration .

Whole specimen of Micromelerpeton credneri. Specimen MB.Am.1210 showing the exceptional quality of preservation of fossil amphibians from the fossil lake deposits of Lake Odernheim. |Scale bar equals 1 cm.

Among amphibians, frogs display some regenerative capacity and can fully regenerate their limbs until the tadpole reaches metamorphic climax and similar molecular markers controlling certain aspects of the regeneration cascade have been found in premetamorphic frogs and salamanders . As differentiation advances, the regenerative capacity of frogs gradually decreases and regenerative failure is correlated with an orderly reduction in the number of regenerated digits, inverse to the order of initial digit development  until regenerative capacity is lost in the adult animal with metamorphic climax . Outside of sarcopterygians, a recent study showed that the basal actinopterygian Polypterus is capable of fully regenerating its pectoral fins at least until individuals reach reproductive age .

The question of which molecular and evolutionary differences between salamanders and other tetrapods are responsible for the high regenerative capacities of salamanders thus far remains largely unresolved. Many of the molecular mechanisms controlling regeneration of different tissues have been shown to be shared in animal regeneration . However, limb regeneration is considered one of the most complex regenerative modes, and recent studies have identified a number of specific molecular markers that seem to be unique to salamander limb regeneration .

Abstract

Salamanders are the only tetrapods capable of fully regenerating their limbs throughout their entire lives. Much data on the underlying molecular mechanisms of limb regeneration have been gathered in recent years allowing for new comparative studies between salamanders and other tetrapods that lack this unique regenerative potential. By contrast, the evolution of animal regeneration just recently shifted back into focus, despite being highly relevant for research designs aiming to unravel the factors allowing for limb regeneration. We show that the 300-million-year-old temnospondyl amphibian Micromelerpeton, a distant relative of modern amphibians, was already capable of regenerating its limbs. A number of exceptionally well-preserved specimens from fossil deposits show a unique pattern and combination of abnormalities in their limbs that is distinctive of irregular regenerative activity in modern salamanders and does not occur as variants of normal limb development. This demonstrates that the capacity to regenerate limbs is not a derived feature of modern salamanders, but may be an ancient feature of non-amniote tetrapods and possibly even shared by all bony fish. The finding provides a new framework for understanding the evolution of regenerative capacity of paired appendages in vertebrates in the search for conserved versus derived molecular mechanisms of limb regeneration.

Reference :
Nadia B. Fröbisch, Constanze Bickelmann, Florian Witzmann
DOI: 10.1098/rspb.2014.1550

Note : The above story is based on materials provided by The Royal Society.

Unveiling the origin of parental care in Mesozoic carrion beetles

Left: silphid from the Middle Jurassic Daohugou biota (165 Ma); middle: silphid from the Early Cretaceous Jehol biota (125 Ma); right, silphid from the earliest Late Cretaceous Burmese amber (99 Ma).

The reconstruction of the early stages of social evolution in the fossil record is a challenge, as these behaviors often do not leave concrete traces. Among these behaviors, parental care represents a significant behavioral adaptation in life history and, as one of the core levels of arthropod sociality, has a wealth of sociobiological and behavioral ecological theory. Parental care has evolved independently numerous times among animals, including various lineages of insects and many vertebrates, including dinosaurs.
Professor HUANG Diying from the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences and his team, reported a unique discovery of diverse transitional carrion beetles (Silphidae) from the Middle Jurassic Daohugou biota (ca. 165 Ma) at Ningcheng County, Inner Mongolia, the Early Cretaceous Jehol biota (ca. 125 Ma) at Beipiao City, Liaoning Province of China and the mid-Cretaceous Burmese amber (ca. 99 Ma). The research is published online in Proceedings of the National Academy of the Sciences (P.N.A.S.) on September 16, 2014.

With fewer than 200 extant species, Silphidae are among the largest and most conspicuous of the staphylinoid Coleoptera. Silphid parental care has been intensively studied with several attempts to explain its origin and subsequent evolution. Fossil evidence that elucidates the origin and evolutionary history of this phenomenon is lacking, although modern-looking silphids have been discovered from the Late Eocene (ca. 35 Ma) of Florissant, Colorado. In recent years, HUANG Diying and his PhD student CAI Chenyang have collected a large number of well-preserved Mesozoic silphids, including 37 specimens from the Daohugou biota, 5 specimens from the Jehol biota, and 6 individuals preserved in Burmese amber, which provides new insights into the origin and early evolution of elaborate parental care in Silphidae.

The diverse silphids from Daohugou extend the earliest records of the family by about 130 million years, while they are close to modern forms as evidenced by their clubbed antennae, large mesoscutellum and truncate elytra. SEM studies show that two types of sensory organs are recognizable on the antennal club of the Jurassic silphids, perfectly corresponding to those in extant nicrophorine beetles, namely sensilla coelosphaerica and sensilla basiconica. The identical olfactory structures indicate that silphids in the Jurassic were already adapted to detecting sulfur-containing volatile organic compounds over long ranges, just as in extant nicrophorines and most silphines. Mesozoic silphids may have been significant scavengers and important to the breakdown and recycling of carcasses in such ancient ecosystems before the emergence of blow flies (Calliphoridae).

The Cretaceous silphids, although very similar to the Jurassic ones, possess a pair of stridulatory files on abdominal tergite used in parent-offspring communication like those found in extant Nicrophorinae. The modern Nicrophorus (burying beetles) can provide elaborate biparental care to their offspring, including exploiting small vertebrate carcasses (early birds or mammals) and burying them in soil as a source of nutrition for their larvae. The buying beetles are well known as subsocial insects. The innovation of stridulatory files in Nicrophorinae for parent-offspring communication and defense is critically linked to the origin of parental care. Competition for resources and predation has been hypothesized as ecological factors important to the evolution of parental care. Before the emergence of the potential competitors such as blow flies, the threat of predation, potentially by some derived staphylinine rove beetles (Staphylinidae) with large predatory mandibles, may have triggered the origin of parental care among ancient carrion beetles.

The subsocial carrion beetles from the Jehol biota represent the oldest fossil record for (sub-) social insects, older than earliest ants from mid-Cretaceous French amber (ca. 100 Ma), the earliest bees from Burmese amber (ca. 99 Ma) and the earliest termites. Although the Mesozoic silphids from China are very similar to some modern forms, they have significantly different antennal types, while slightly younger silphids from Burmese amber have lamellate antennae are very morphologically close to modern burying beetles. These mid-Cretaceous burying beetles may have exploited and buried small rodents or birds (usually < 200 gram) as a source of nutrition for their larvae

With the origin of derived mammals in the Late Triassic, early silphids might have already derived from their staphyliniform ancestors at that time. The continuous presence of carrion in the early ecosystem probably resulted in very little change of silphid morphology.

The research was supported by the National Basic Research Program of China, Outstanding Youth Foundation of Jiangsu Province, and the National Natural Science Foundation of China.

Reference :
Chen-Yang Cai, Margaret K. Thayer, Michael S. Engel, Alfred F. Newton, Jaime Ortega-Blanco, Bo Wang, Xiang-Dong Wang, and Di-Ying Huang*, 2014：Early origin of parental care in Mesozoic carrion beetles. P.N.A.S., doi/10.1073/pnas.1412280111

Note : The above story is based on materials provided by Nanjing Institute of Geology and Palaeontology Chinese Academy of Sciences.

New meat-eating dinosaur lived in the wake of a mass extinction

Tachiraptor, a 1.5-meter-long theropod dinosaur (center) that lived in what is now Venezuela just over 200 million years ago, is a close cousin of dinosaurs that later evolved into multiton meat eaters such as Allosaurus. Credit : Maurílio Oliveira

A newly described dinosaur, whose fossils are some of the first to be unearthed in Venezuela, turns out to be the close, relatively small kin of creatures that later evolved into multiton meat eaters such as Allosaurus and Tyrannosaurus rex. The creature, and another dinosaur whose fossils were found nearby and reported just 2 months ago, are filling in gaps in the fossil record and revealing new insights into dinosaur evolution in the wake of a mass extinction that happened about 201 million years ago.
The new species, dubbed Tachiraptor admirabilis, is a predator that gets part of its name from the Venezuelan state of Táchira, where the fossils were found. Only two bones of the ancient species have been unearthed, says Max Langer, a vertebrate paleontologist at the University of São Paulo in Brazil. Nevertheless, those bits (each from a different individual, and one of them not even a complete bone) tell scientists a lot, Langer notes.

The bones, both from the creature’s lower leg, show the dinosaur likely measured about 1.5 meters from nose to tail, Langer says. Their general size and shape mark the creature as a theropod, a bipedal meat eater. The bones differ enough from those of other theropods to indicate that the dino is a new species, Langer and his colleagues report today in Royal Society Open Science.

The now-solid rocks surrounding the fossils, which were laid down as sediments on an ancient flood plain, also tell a story. By age dating zircons—tiny crystals that typically include uranium as a trace element—in the rocks, Langer and his colleagues estimate that the sediments were deposited about 200.7 million years ago. At that time, the region—a volcanically active rift valley where Gondwana, a remnant of the supercontinent Pangaea, was itself splitting apart—sat near Earth’s equator. The period was also less than 1 million years after the mass extinction that marked the end of the Triassic period and the beginning of the Jurassic—an event that, like the dino die-offs that occurred about 65 million years ago, may have been triggered by an extraterrestrial impact.

“These survivors of the Triassic-Jurassic mass extinction were the ‘ground zero’ for later theropod evolution,” says Thomas Holtz Jr., a vertebrate paleontologist at the University of Maryland, College Park, who was not involved in the study. Plus, he notes, theropod fossils from this era from anywhere in the world aren’t common, so the new finds reveal what some theropods of that era looked like and will be particularly useful to researchers trying to flesh out the dinosaur family tree. The new study, he says, “shows that important discoveries don’t have to be of the biggest or the scariest [dinosaurs].”

The first dinosaur reported from this region, which lived in the same area and at the same time as Tachiraptor, was unveiled in August. That creature, dubbed Laquintasaura, was slightly smaller than Tachiraptor but had the same general appearance despite being a member of a different group of dinosaurs called ornithischians, says Richard Butler, a vertebrate paleontologist at the University of Birmingham in the United Kingdom and a member of the team that described Laquintasaura. “All the small dinosaurs of that era looked about the same,” he notes, but subtle skeletal differences help distinguish the carnivorous theropods from their herbivorous and omnivorous relatives.

The last common ancestor of theropods and ornithischians, a creature as-yet undiscovered, probably looked a lot like Tachiraptor and Laquintasaura, Butler says. Only millions of years later did many species within these groups evolve great size and distinct appearances, he notes.

More fossils from this region could help paleontologists refine the dinosaur family tree further, Langer says. But such work may be a long slog, he suggests, because rocks that might hold fossils aren’t readily accessible: The recent discoveries, which were unearthed at sites where highway excavations sliced through heavily vegetated hillsides, came only after 2 decades of looking for such fossils.

Note : The above story is based on materials provided by American Association for the Advancement of Science. The original article was written by Sid Perkins.

Carnivorous plants from the Baltic amber forest

Fossil leaf of a flypaper trap plant in Baltic amber. Photo: PNAS and University of Göttingen/Alexander Schmidt.

Researchers from the Universities of Göttingen and Bielefeld and the Botanical State Collection of Munich, led by paleontologist Professor Alexander Schmidt from the University of Göttingen, have found the world’s first fossils of a carnivorous flypaper trap plant. Both fossil leaves, covered with glandular hairs, are enclosed in a piece of Baltic amber. The amber comes from a mine near Kaliningrad in Russia and is about 35 to 47 million years old. So far, the fossil evidence of carnivorous plants was just of seeds and pollen belonging to the sundew family. The results were published in Proceedings of the National Academy of Sciences of the USA (PNAS).

Baltic amber is one of the world’s largest amber deposits and contains many inclusions of animals and plants. PhD student Eva-Maria Sadowski at the University of Göttingen examines these plant fossils in order to reconstruct the vanished Eocene flora. “The most striking features are the long-stalked multicellular glands, which are also called tentacles, covering the lower leaf surface and the margins of the leaf fossils,” says Eva-Maria Sadowski. These tentacles and other morphological details match the adhesive flypaper traps of the living carnivorous plant Roridula, today restricted to only a few places in South Africa. With their long sticky tentacles Roridula catches a large number of insects, but it does not produce enzymes for prey digestion, unlike most other carnivorous plants. However, heteropteran insects live in association with Roridula, and these bugs feed on the caught prey. To obtain additional nutrients, Roridula incorporates the nutrient-rich excretions of these bugs through their leaves. The highly efficient Roridula insect trap is organized into different tentacle size classes that were also detected in the fossil leaves. In addition, the micromorphology of their glandular heads and adhered organic remains indicate an adhesive flypaper trap.

These fossil flypaper traps provide insights into the evolutionary history of carnivorous plants. Originally, it was assumed that the ancestors of Roridula originated about 90 million years ago in Africa and evolved in isolation after the breakup of the southern continent Gondwana. “The new fossils from Baltic amber show that the ancestors of Roridula plants occurred in the northern hemisphere until 35 million years ago, and that they were not restricted to South Africa,” explains Prof. Alexander Schmidt. Roridula belongs to the plant family Roridulaceae and is related to the carnivorous American pitcher plants, the Sarraceniaceae. “Our results not only fill a gap in our knowledge about the historical distribution of the Roridulaceae, but also confirm molecular dating analyses, according to which the Roridulaceae exist as a distinct plant family for at least 38 million years,” says Dr. Andreas Fleischmann, carnivorous plant expert at the Botanical State Collection of Munich, who participated in the study. “Both carnivorous plant leaves from Baltic amber are important for understanding the evolutionary history and distribution of carnivorous plants. However, they also show us the high plant diversity of the Baltic amber forest, “says Eva-Maria Sadowski.

Reference:
Eva-Maria Sadowski et al. (2014). Carnivorous leaves from Baltic amber. Proceedings of the National Academy of Sciences of the USA. doi: 10.1073/pnas.1414777111.

Note : The above story is based on materials provided by University of Göttingen. The original article was written by Professor Alexander Schmidt & Eva-Maria Sadowski.

Oldest ever engraving discovered on 500,000-year-old shell

Detail of the engraving on fossil Pseudodon shell (DUB1006-fL) from Trinil. Credit: Wim Lustenhouwer, VU University Amsterdam

Homo erectus on Java was already using shells of freshwater mussels as tools half a million years ago, and as a ‘canvas’ for an engraving. An international team of researchers, led by Leiden archaeologist José Joordens, published this discovery on 3 December in Nature. The discovery provides new insights into the evolution of human behaviour.

Not only Homo sapiens made engravings

“Until this discovery, it was assumed that comparable engravings were only made by modern humans (Homo sapiens) in Africa, starting about 100,000 years ago,” says lead author José Joordens, researcher at the Faculty of Archaeology at Leiden University.

A team of 21 researchers studied hundreds of fossil shells and associated finds and sediments from the Homo erectus site Trinil, on the Indonesian island of Java. The shells are part of the Dubois Collection that has been held at the Naturalis Biodiversity Center since the end of the 19th century. The shells were excavated by the Dutch physician and researcher Eugène Dubois, the discoverer of Pithecanthropus erectus — now known as Homo erectus.

Engravings older than weathering

The discovery of an engraved geometrical pattern on one of the shells came as a total surprise. The zig zag pattern, that can only be seen with oblique lighting, is clearly older than the weathering processes on the shell arising from fossilisation. The study has excluded the possibility that the pattern could have been caused by animals or by natural weathering processes and shows that the ‘zigzag’ pattern is the work of Homo erectus.

Five hundred thousand years old

By applying two dating methods, researchers at the VU University Amsterdam and Wageningen University have determined that the shell with the engraving is minimally 430,000 and maximally 540,000 years old.This means that the engraving is at least four times older than the previously oldest known engravings, found in Africa.

Purpose or meaning of the engraving?

“It’s fantastic that this engraved shell has been discovered in a museum collection where it has been held for more than a hundred years. I can imagine people may be wondering whether this can be seen as a form of early art,” says Wil Roebroeks, Professor of Palaeolithic Archaeology at Leiden University. He was able to finance this long-term research with his NWO Spinoza Prize. “At the moment we have no clue about the meaning or purpose of this engraving.”

Early human-like mussel collector

This research has shown that these early human-like people were very clever about how they opened these large freshwater mussels; they drilled a hole through the shell using a sharp object, possibly a shark’s tooth, exactly at the point where the muscle is attached that keeps the shell closed. “The precision with which these early humans worked indicates great dexterity and detailed knowledge of mollusc anatomy,” says Frank Wesselingh, a researcher and expert on fossil shells at Naturalis. The molluscs were eaten and the empty shells were used to manufacture tools, such as knives.

Possible follow-on research

This discovery from the historical Dubois collection sheds unexpected new light on the skills and behaviour of Homo erectus, and indicates that Asia is a promising and, so far, relatively unexplored area for finding intriguing artefacts.

From the Netherlands, researchers at Leiden University, the Naturalis Biodiversity Center, the Vrije Universiteit Amsterdam, the universities of Wageningen and Delft and the Cultural Heritage Agency of the Netherlands were involved in the research.

This research is being financed by research funding from the NWO Spinoza Prize.

The shell with the oldest known human engraving will be on display in the Naturalis museum from 4 December onward.

Video:

References:
– Joordens J.C.A., d’Errico F., Wesselingh F.P., Munro S. de Vos, J., Wallinga, J. Ankjærgaard, C., Reimann, T., Wijbrans, J.R., Kuiper K.F., Mücher H.J., Coqueugniot, H., Prié, H.V., Joosten, I., van Os, B., Schulp, A.S., Panuel, M., van der Haas V., Lustenhouwer W., Reijmer J.J.G., Roebroeks, W. Homo erectus at Trinil on Java used shells for tool production and engraving. Nature, December 2014 DOI: 10.1038/nature19362

– Josephine C. A. Joordens, Francesco d’Errico, Frank P. Wesselingh, Stephen Munro, John de Vos, Jakob Wallinga, Christina Ankjærgaard, Tony Reimann, Jan R. Wijbrans, Klaudia F. Kuiper, Herman J. Mücher, Hélène Coqueugniot, Vincent Prié, Ineke Joosten, Bertil van Os, Anne S. Schulp, Michel Panuel, Victoria van der Haas, Wim Lustenhouwer, John J. G. Reijmer, Wil Roebroeks. Homo erectus at Trinil on Java used shells for tool production and engraving. Nature, 2014; DOI: 10.1038/nature13962

Note : The above story is based on materials provided by Leiden University.

New math model examines mixing fronts in porous media flows

The concentration field of the invading reactant A. The system is in the stretching regime, and the reaction front is organized in independent stretched lamellae. The inset in (a) displays a close-up view of the concentration gradient field and its width. (b) The reactants interface.

Analyzing what happens where interfaces meet and mix is essential toward understanding and controlling fundamental mechanisms in both natural and industrial systems. By considering the reaction front of heterogeneous fluid flows in porous media, whose reaction rates are sharply influenced by compression and diffusion, researchers from Massachusetts Institute of Technology, Spanish National Research Council, Université de Rennes 1 (France), and Pacific Northwest National Laboratory developed a new model for predicting reaction front kinetics in these flows that provides a more complete assessment regarding the effects of many processes—stretching, coalescence, and fluid particle dispersion—on reactive transport dynamics.

Understanding the dynamics of mixing on reaction kinetics at the pore scale can directly influence the quality and usability of models used to measure reactive transport in carbon dioxide storage, subsurface flow and transport (contaminant transport/reactivity in hydrological systems), or mixing-driven biochemical processes in filters and/or living tissues. Each of these areas has distinct relevance to current U.S. Department of Energy mission objectives.

As fluids traverse the porous media, they form thin, membrane-like structures, or lamellae, that ultimately coalesce. These lamella-like structures evolve due to compression, diffusion, and merging, which governs the temporal evolution of the global reaction rates. In their work, the researchers considered two reactants (A and B) mixed to form a product C, according to the irreversible reaction A + B → C, in a solution flowing through a porous medium whose heterogeneity determined the front geometry. They used the smoothed particle hydrodynamics (SPH) method to solve the governing Navier-Stokes and advection-diffusion-reaction equations.

In their four simulations (Péclet number values, Pe = 0.071, 0.71, 2.4, and 7.1), they saw how flow affected mixing. In the “stretching regime,” the interface between the reactants organized into complex, elongated lamellae. As the reactant lamellae began to coalesce by diffusion, the process became less linear, and the interface width decreased due to compression induced by the flow stretching. Meanwhile, during the “coalescence regime,” the front topology changed, forming an aggregate of lamellae bundles. The researchers determined that the number of bundles in a pore is inversely proportional to the interface width, which limits the available space for them to coexist. As width increased, the bundles continued to merge, decreasing their numbers. This happens because the local diffusive growth contributes to bundle coalescence—but not to growth of the mixing area. Thus, the dominant effect for mixing in this regime is fluid advection.

The generated model accounted for the competition between compression and diffusion in the evolving concentration gradients, as well as the dynamics of the lamella merging in a unique formulation.

“The proposed model is applicable for various reactive systems, not just for flow in porous media. In most natural and engineered reactive systems, the large-scale behavior depends closely on the mixing and reactions occurring at the microscale,” explained Dr. Alexandre Tartakovsky, associate division director for computational mathematics at PNNL and a co-author of the paper.

“This new method provides a more complete look at the reaction front kinetics—one that accounts for compression, diffusion, and lamellae behaviors—rather than being based solely on geometric analysis,” he added. “It has great potential for improving reactive transport modeling used in a range of applications.”

While this novel simulation elucidates the role of chemical reaction dynamics in heterogeneous mixing fronts and offers new perspectives for upscaling reaction kinetics in heterogeneous flows through porous media, the model has potential for wider applicability to other heterogeneous flow analyses.

Reference:
de Anna P, M Dentz, A Tartakovsky, and T Le Borgne. 2014. “The filamentary structure of mixing fronts and its control on reaction kinetics in porous media flows.” Geophysical Research Letters 41(13):4586-4593. DOI: 10.1002/2014GL060068.

Note : The above story is based on materials provided by Pacific Northwest National Laboratory.

Turn back the molecular clock, say Argentina’s plant fossils

This leafy branch of the fossil kauri tree Agathis zamunerae from Patagonia, 52 million years old. Molecular dates suggested that kauris are less than half that age. Credit: Peter Wilf

Molecular clocks — based on changes in genetic material — indicate much younger ages for a wide variety of plants found as fossils in southern Argentina than do the solid, geologic dates of those fossils, according to geoscientists who surveyed recent paleobotanical discoveries in Patagonia.
The finding suggests serious biases in molecular clocks, which are heavily used to date many kinds of living things. It also directly refutes a widely-held idea about how most Southern Hemisphere plant and animal groups attained their current distributions.

Geologists date fossils by radioisotopic analysis, which can produce absolute ages with uncertainties less than 0.05 percent. Molecular clocks apply rates of molecular change and fossil ‘calibrations’ to the tree of life to construct a ‘timetree’ that estimates when evolutionary events occurred. Substitution rates come from DNA found in multiple genes, and known, dated fossils provide the calibration anchor points. Even though the clock method’s stated errors are much larger than for geologic dating, it offers the hugely appealing advantage of dating the large proportion of living organisms that have very limited, or no, fossil record.

“Paleontology and molecular clocks have a long, uneasy relationship,” said Peter Wilf, a paleobotanist and professor of geoscience, Penn State. “Paleontologists want molecular clocks to work. However, for years we have seen molecular dates, mostly for very deep evolutionary events, that are much older than the corresponding fossils. This situation has been a frustrating Catch-22 because if the clocks are wrong, no fossils exist that could demonstrate they are wrong. Here, we looked at many new plant fossils from the extremely productive region of Patagonia, and we found the opposite, that the fossils are much older than the clock dates. In this case, we can definitely say that the clocks are wrong. The fossils prove it.”

Wilf, Ignacio Escapa, National Scientific and Technical Research Council, Egidio Feruglio Paleontology Museum (MEF), Trelew, Argentina, and many others have worked on Patagonian paleobotany together based at Penn State, MEF, and Cornell University for more than a decade.

We are dealing with one of the most recent controversies in biological sciences,” said Escapa. “Is it possible to determinate the tempo of evolution without an exhaustive analysis of the fossil record? The extremely diverse fossil record emerging from Patagonia seems to indicate that this is not currently possible.”

Wilf and Escapa looked at 19 fossil plant lineages of ferns, cycads, conifers and flowering plants from Patagonia, Argentina and compared their ages to molecular clock studies that used other fossils as calibrations. They reported their results today (Dec. 2) online in New Phytologist. They found that most of the fossil dates are significantly older than those determined by the molecular clock data, unless a previous calibration was already very closely related to the target fossil. The work’s further significance lies in the fact that all the fossils examined represent plants that lived on the supercontinent Gondwana, in its terminal stage.

“We targeted our study towards one of the greatest debates in biology: what explains the disjunct distributions of so many plant and animal groups on different southern land masses separated by vast oceans?” said Wilf. “These land masses were once joined in Gondwana, and one famous school of thought, known as vicariance biogeography, holds that the modern distributions mostly result from the subsequent separations of the continents and the organisms that lived on them. On the other hand, molecular ‘timetrees’ increasingly place many evolutionary events after the final breakup of Gondwana, about 45 million years ago.”

This explanation requires that many plant and animal groups evolved relatively recently, then somehow dispersed across the oceans. The vast accumulation of young molecular dates has convinced many researchers that this striking idea is correct.

“However, what we see in these fossils is that classic Southern Hemisphere plants, like the monkey puzzle trees that now inhabit South America and Australasia, lived on Gondwana long before it broke up.” said Wilf. “Transoceanic travel is not required to explain their past and present distributions, and our results will reinvigorate the vicariance school. However, we caution that dispersal across oceans probably still played an important role, though diminished from what many have thought recently.”

Gondwana was once composed of most of the land that is now in the Southern Hemisphere, plus India. At its last stage 45 million years ago, it still included Antarctica, South America, and Australia. The researchers’ results show that living plant groups found as fossils across the Southern Hemisphere evolved while there were still land connections or shallow water between these continents. In many cases, no long distance, deep-water crossings were necessary to achieve the distributions of the fossils’ living relatives.

Fossil plants from Patagonia are a superb resource for comparing geologic and molecular dates. Not only do fossils have accurate geological dates, but the taxonomic information on those fossils is well known because of their excellent preservation and completeness. There is now a large amount of new, high-quality information emerging from Patagonia that has not yet been assimilated into molecular dating studies, offering this rare opportunity to compare fossils and clocks for a relatively large number of plant groups.

The researchers are not certain why there is strong directional bias in these molecular clock dates. They suggest that some molecular clock studies omitted known fossils, which would have made the dates older. They also suggest that the conventions for placing fossils on the tree of life as calibrations are too conservative and seem to bias molecular estimates significantly toward younger dates.

The inaccuracy of the molecular clocks in this study raises new doubts about the accuracy of clock dates for many other organisms, from animals to human pathogens. The work bolsters the importance of continuing to find new fossils of important plant and animal groups from the many undersampled regions of the world. However, even though the dialogue between paleontologists and molecular biologists is often difficult, the researchers agree that it must continue so that a broader understanding can emerge.

“Discovery and description of new and exciting fossils, together with real interdisciplinary efforts, may be the single best opportunity to develop a clear consensus about this important issue in the evolution of life,” said Escapa.

Reference:
Peter Wilf, Ignacio H. Escapa. Green Web or megabiased clock? Plant fossils from Gondwanan Patagonia speak on evolutionary radiations. New Phytologist, 2014; DOI: 10.1111/nph.13114

Note : The above story is based on materials provided by Penn State. The original article was written by A’ndrea Elyse Messer.

Most ancient pinworm yet found was infected with parasitic nematodes

Scott Gardner. Credit: Craig Chandler, University Communications.

An egg much smaller than a common grain of sand and found in a tiny piece of fossilized dung has helped scientists identify a pinworm that lived 240 million years ago.

It is believed to be the most ancient pinworm yet found in the fossil record.
The discovery confirms that herbivorous cynodonts — the ancestors of mammals — were infected with the parasitic nematodes. It also makes it even more likely that herbivorous dinosaurs carried pinworms.

Scott Gardner, a parasitologist and director of the Harold W. Manter Laboratory of Parasitology at the University of Nebraska-Lincoln, was among an international group of scientists who published the study in the journal Parasites & Vectors.

“This discovery represents a first for our team and I think it opens the door to finding additional parasites in other species of fossil organisms,” he said.

The team found the pinworm egg in a coprolite — fossilized feces — collected in 2007 at an excavation site in Rio Grande do Sul state in southern Brazil.

The coprolite was collected at a site with abundant fossilized remains of cynodonts. Previously, an Ascarid-like egg — resembling a species of nematode commonly found in modern-day mammals — was found in the coprolite.

The pinworm egg, representing an undescribed or “new species,” was named Paleoxyuriscockburni, in honor of Aidan Cockburn, founder of the Paleopathology Association.

The structure of the pinworm egg placed it in a biological group of parasites that occur in animals that ingest large amounts of plant material. Its presence helped scientists deduce which cynodont species, of several found at the collection site, most likely deposited the coprolite.

Since the field of paleoparasitology, or the study of ancient parasites, emerged in the early 20th century, scientists have identified parasites of both plants and animals that date back as far as 500 million years ago.

The study of parasites in ancient animals can help determine the age of fossilized organisms and help establish dates of origin and diversification for association between host species and parasites. Coprolites are a key part of the study, enabling a better understanding of the ecological relationships between hosts and parasites.

Other members of the team were Jean-Pierre Hugot of the National Museum of Natural History in Paris; Victor Borba, Juliana Dutra, Luiz Fernando Ferreira and Adauto Araujo of Oswaldo Cruz Foundation in Rio de Janeiro; Prisiclla Araujo and Daniela Leles of Fluminense Federal University in Rio de Janeiro; and Atila August Stock Da-Rosa of the Federal University of Santa Maria in Rio Grande do Sul.

Reference:
Jean-Pierre Hugot, Scott L Gardner, Victor Borba, Priscilla Araujo, Daniela Leles, Átila Augusto Stock Da-Rosa, Juliana Dutra, Luiz Fernando Ferreira, Adauto Araújo. Discovery of a 240 million year old nematode parasite egg in a cynodont coprolite sheds light on the early origin of pinworms in vertebrates. Parasites & Vectors, 2014; 7 (1) DOI: 10.1186/s13071-014-0486-6

Note : The above story is based on materials provided by University of Nebraska-Lincoln. The original article was written by Leslie Reed.

Traces of Martian biological activity could be locked inside a meteorite

Ejected from Mars after an asteroid crashed on its surface, the meteorite, named Tissint, fell on the Moroccan desert on July 18, 2011, in view of several eyewitnesses. Upon examination, the alien rock was found to have small fissures that were filled with carbon-containing matter. Credit: Copyright Alain Herzog/EPFL

Did Mars ever have life? Does it still? A meteorite from Mars has reignited the old debate. An international team that includes scientists from EPFL has published a paper in the scientific journal Meteoritics and Planetary Sciences, showing that martian life is more probable than previously thought.
“So far, there is no other theory that we find more compelling,” says Philippe Gillet, director of EPFL’s Earth and Planetary Sciences Laboratory. He and his colleagues from China, Japan and Germany performed a detailed analysis of organic carbon traces from a Martian meteorite, and have concluded that they have a very probable biological origin. The scientists argue that carbon could have been deposited into the fissures of the rock when it was still on Mars by the infiltration of fluid that was rich in organic matter.

Ejected from Mars after an asteroid crashed on its surface, the meteorite, named Tissint, fell on the Moroccan desert on July 18, 2011, in view of several eyewitnesses. Upon examination, the alien rock was found to have small fissures that were filled with carbon-containing matter. Several research teams have already shown that this component is organic in nature. But they are still debating where the carbon came from.

Maybe biological, but not from our planet

Chemical, microscopic and isotope analysis of the carbon material led the researchers to several possible explanations of its origin. They established characteristics that unequivocally excluded a terrestrial origin, and showed that the carbon content were deposited in the Tissint’s fissures before it left Mars.

The researchers challenged previously described views (Steele et al., Science, 2012) proposing that the carbon traces originated through the high-temperature crystallization of magma. According to the new study, a more likely explanation is that liquids containing organic compounds of biological origin infiltrated Tissint’s “mother” rock at low temperatures, near the Martian surface.

These conclusions are supported by several intrinsic properties of the meteorite’s carbon, e.g. its ratio of carbon-13 to carbon-12. This was found to be significantly lower than the ratio of carbon-13 in the CO2 of Mars’s atmosphere, previously measured by the Phoenix and Curiosity rovers. Moreover, the difference between these ratios corresponds perfectly with what is observed on Earth between a piece of coal — which is biological in origin — and the carbon in the atmosphere. The researchers note that this organic matter could also have been brought to Mars when very primitive meteorites — carbonated chondrites — fell on it. However, they consider this scenario unlikely because such meteorites contain very low concentrations of organic matter.

“Insisting on certainty is unwise, particularly on such a sensitive topic,” warns Gillet. “I’m completely open to the possibility that other studies might contradict our findings. However, our conclusions are such that they will rekindle the debate as to the possible existence of biological activity on Mars — at least in the past.”

Video:

Reference:
Yangting Lin, Ahmed El Goresy, Sen Hu, Jianchao Zhang, Philippe Gillet, Yuchen Xu, Jialong Hao, Masaaki Miyahara, Ziyuan Ouyang, Eiji Ohtani, Lin Xu, Wei Yang, Lu Feng, Xuchao Zhao, Jing Yang, Shin Ozawa. NanoSIMS analysis of organic carbon from the Tissint Martian meteorite: Evidence for the past existence of subsurface organic-bearing fluids on Mars. Meteoritics & Planetary Science, 2014; 49 (12): 2201 DOI: 10.1111/maps.12389

Note : The above story is based on materials provided by Ecole Polytechnique Fédérale de Lausanne.

Losing air:New study finds a barrage of small impacts likely erased much of the Earth’s primordial atmosphere.

Today’s atmosphere likely bears little trace of its primordial self: Geochemical evidence suggests that Earth’s atmosphere may have been completely obliterated at least twice since its formation more than 4 billion years ago. Credit: Image courtesy of NASA

Today’s atmosphere likely bears little trace of its primordial self: Geochemical evidence suggests that Earth’s atmosphere may have been completely obliterated at least twice since its formation more than 4 billion years ago. However, it’s unclear what interplanetary forces could have driven such a dramatic loss.
Now researchers at MIT, Hebrew University, and Caltech have landed on a likely scenario: A relentless blitz of small space rocks, or planetesimals, may have bombarded Earth around the time the moon was formed, kicking up clouds of gas with enough force to permanently eject small portions of the atmosphere into space.

Tens of thousands of such small impacts, the researchers calculate, could efficiently jettison Earth’s entire primordial atmosphere. Such impacts may have also blasted other planets, and even peeled away the atmospheres of Venus and Mars.

In fact, the researchers found that small planetesimals may be much more effective than giant impactors in driving atmospheric loss. Based on their calculations, it would take a giant impact — almost as massive as Earth slamming into itself — to disperse most of the atmosphere. But taken together, many small impacts would have the same effect, at a tiny fraction of the mass.

Hilke Schlichting, an assistant professor in MIT’s Department of Earth, Atmospheric and Planetary Sciences, says understanding the drivers of Earth’s ancient atmosphere may help scientists to identify the early planetary conditions that encouraged life to form.

“[This finding] sets a very different initial condition for what the early Earth’s atmosphere was most likely like,” Schlichting says. “It gives us a new starting point for trying to understand what was the composition of the atmosphere, and what were the conditions for developing life.”

Schlichting and her colleagues have published their results in the journal Icarus.

Efficient ejection

The group examined how much atmosphere was retained and lost following impacts with giant, Mars-sized and larger bodies and with smaller impactors measuring 25 kilometers or less — space rocks equivalent to those whizzing around the asteroid belt today.

The team performed numerical analyses, calculating the force generated by a given impacting mass at a certain velocity, and the resulting loss of atmospheric gases. A collision with an impactor as massive as Mars, the researchers found, would generate a shockwave through Earth’s interior, setting off significant ground motion — similar to simultaneous giant earthquakes around the planet — whose force would ripple out into the atmosphere, a process that could potentially eject a significant fraction, if not all, of the planet’s atmosphere.

However, if such a giant collision occurred, it should also melt everything within the planet, turning its interior into a homogenous slurry. Given the diversity of noble gases like helium-3 deep inside Earth today, the researchers concluded that it is unlikely that such a giant, core-melting impact occurred.

Instead, the team calculated the effects of much smaller impactors on Earth’s atmosphere. Such space rocks, upon impact, would generate an explosion of sorts, releasing a plume of debris and gas. The largest of these impactors would be forceful enough to eject all gas from the atmosphere immediately above the impact’s tangent plane — the line perpendicular to the impactor’s trajectory. Only a fraction of this atmosphere would be lost following smaller impacts.

To completely eject all of Earth’s atmosphere, the team estimated, the planet would need to have been bombarded by tens of thousands of small impactors — a scenario that likely did occur 4.5 billion years ago, during a time when the moon was formed. This period was one of galactic chaos, as hundreds of thousands of space rocks whirled around the solar system, frequently colliding to form the planets, the moon, and other bodies.

“For sure, we did have all these smaller impactors back then,” Schlichting says. “One small impact cannot get rid of most of the atmosphere, but collectively, they’re much more efficient than giant impacts, and could easily eject all the Earth’s atmosphere.”

Runaway effect

However, Schlichting realized that the sum effect of small impacts may be too efficient at driving atmospheric loss. Other scientists have measured the atmospheric composition of Earth compared with Venus and Mars. These measurements have revealed that while each planetary atmosphere has similar patterns of noble gas abundance, the budget for Venus is similar to that of chondrites — stony meteorites that are primordial leftovers of the early solar system. Compared with Venus, Earth’s noble gas budget has been depleted 100-fold.

Schlichting realized that if both planets were exposed to the same blitz of small impactors, Venus’ atmosphere should have been similarly depleted. She and her colleagues went back over the small-impactor scenario, examining the effects of atmospheric loss in more detail, to try and account for the difference between the two planets’ atmospheres.

Based on further calculations, the team identified an interesting effect: Once half a planet’s atmosphere has been lost, it becomes much easier for small impactors to eject the rest of the gas. The researchers calculated that Venus’ atmosphere would only have to start out slightly more massive than Earth’s in order for small impactors to erode the first half of the Earth’s atmosphere, while keeping Venus’ intact. From that point, Schlichting describes the phenomenon as a “runaway process — once you manage to get rid of the first half, the second half is even easier.”

Time zero

During the course of the group’s research, an inevitable question arose: What eventually replaced Earth’s atmosphere? Upon further calculations, Schlichting and her team found the same impactors that ejected gas also may have introduced new gases, or volatiles.

“When an impact happens, it melts the planetesimal, and its volatiles can go into the atmosphere,” Schlichting says. “They not only can deplete, but replenish part of the atmosphere.”

The group calculated the amount of volatiles that may be released by a rock of a given composition and mass, and found that a significant portion of the atmosphere may have been replenished by the impact of tens of thousands of space rocks.

“Our numbers are realistic, given what we know about the volatile content of the different rocks we have,” Schlichting notes.

Jay Melosh, a professor of earth, atmospheric, and planetary sciences at Purdue University, says Schlichting’s conclusion is a surprising one, as most scientists have assumed Earth’s atmosphere was obliterated by a single, giant impact. Other theories, he says, invoke a strong flux of ultraviolet radiation from the sun, as well as an “unusually active solar wind.”

“How the Earth lost its primordial atmosphere has been a longstanding problem, and this paper goes a long way toward solving this enigma,” says Melosh, who did not contribute to the research. “Life got started on Earth about this time, and so answering the question about how the atmosphere was lost tells us about what might have kicked off the origin of life.”

Going forward, Schlichting hopes to examine more closely the conditions underlying Earth’s early formation, including the interplay between the release of volatiles from small impactors and from Earth’s ancient magma ocean.

“We want to connect these geophysical processes to determine what was the most likely composition of the atmosphere at time zero, when the Earth just formed, and hopefully identify conditions for the evolution of life,” Schlichting says.

Reference:
Hilke E. Schlichting, Re’em Sari, Almog Yalinewich. Atmospheric mass loss during planet formation: The importance of planetesimal impacts. Icarus, 2015; 247: 81 DOI: 10.1016/j.icarus.2014.09.053

Note : The above story is based on materials provided by Massachusetts Institute of Technology. The original article was written by Jennifer Chu.

Fogo volcano on Sentinel’s radar

Sentinel-1 maps Fogo eruption. Credit: Copernicus data (2014)/ESA/Norut-PPO. labs–COMET-SEOM InSARap study

Radar images from the Sentinel-1A satellite are helping to monitor ground movements of the recently erupted Fogo volcano.

Located on Cape Verde’s Fogo island, the volcano erupted on 23 November for the first time in 19 years and has been active ever since. Lava flows are threatening nearby villages, and local residents have been evacuated.
Radar scans from the Sentinel-1A satellite are being used to study the volcano. The image above – an ‘interferogram’ – is a combination of two radar images from 3 November and 27 November, before and during the eruption.

Deformation on the ground causes changes in radar signals that appear as the rainbow-coloured patterns.

Scientists can use the deformation patterns to understand the subsurface pathways of molten rock moving towards the surface. In this case, the radar shows that the magma travelled along a crack at least 1 km wide.

“By acquiring regular images from Sentinel-1, we will be able to monitor magma movement in the subsurface, even before eruptions take place, and use the data to provide warnings,” said Tim Wright from the University of Leeds and director of the UK Natural Environment Research Council’s Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics.

Mapping for emergency response. Credit: Copernicus

This is particularly valuable in places with few sensors on the ground.

“With this stunning result, the great potential of Sentinel-1 for geophysical applications has been once again unequivocally demonstrated,” said Yngvar Larsen from Norway’s Northern Research Institute, and science leader of ESA’s InSARap project.

Dr Larsen and his team were also involved in mapping the earthquake that struck California’s Napa Valley earlier this year.

Launched in April, Sentinel-1A is the first in a fleet of satellites being developed for Europe’s Copernicus environment monitoring programme. With its radar vision, the Sentinel-1 mission provides an all-weather, day-and-night supply of imagery of Earth’s surface.

Sentinel-1A passes over the same spot on the ground with the same viewing geometry every 12 days. However, once its identical twin, Sentinel-1B, is launched in 2016, this will be cut to just six days, so that changes can be mapped even faster.

“The coverage and repeat visit time of Sentinel-1 is unprecedented and we are currently working on a system that will use Sentinel-1 to monitor all of the visible volcanoes in the world,” said Andy Hooper, also from the University of Leeds.

Note : The above story is based on materials provided by European Space Agency.

What percent of Earth is water?

Earth – Western Hemisphere. Credit: NASA/MODIS/USGS

The Earth is often compared to a majestic blue marble, especially by those privileged few who have gazed upon it from orbit. This is due to the prevalence of water on the planet’s surface. While water itself is not blue, water gives off blue light upon reflection.
For those of us confined to living on the surface, the fact that our world is mostly covered in water is a well known fact. But how much of our planet is made up of water, exactly? Like most facts pertaining to our world, the answer is a little more complicated than you might think, and takes into account a number of different qualifications.

In simplest terms, water makes up about 71% of the Earth’s surface, while the other 29% consists of continents and islands.

To break the numbers down, 96.5% of all the Earth’s water is contained within the oceans as salt water, while the remaining 3.5% is freshwater lakes and frozen water locked up in glaciers and the polar ice caps. Of that fresh water, almost all of it takes the form of ice: 69% of it, to be exact. If you could melt all that ice, and the Earth’s surface was perfectly smooth, the sea levels would rise to an altitude of 2.7 km.

Aside from the water that exists in ice form, there is also the staggering amount of water that exists beneath the Earth’s surface. If you were to gather all the Earth’s fresh water together as a single mass (as shown in the image above) it is estimated that it would measure some 1,386 million cubic kilometers (km3) in volume.

Meanwhile, the amount of water that exists as groundwater, rivers, lakes, and streams would constitute just over 10.6 million km3, which works out to a little over 0.7%. Seen in this context, the limited and precious nature of freshwater becomes truly clear.

But how much of Earth is water—how much water contributes to the actual mass of the planet? This includes not just the surface of the Earth, but inside as well. Scientists calculate that the total mass of the oceans on Earth is 1.35 x 1018 metric tonnes, which is 1/4400 the total mass of the Earth. In other words, while the oceans cover 71% of the Earth’s surface, they only account for 0.02% of our planet’s total mass.

The origin of water on the Earth’s surface, as well as the fact that it has more water than any other rocky planet in the Solar System, are two of long-standing mysteries concerning our planet.

Not that long ago, it was believed that our planet formed dry some 4.6 billion years ago, with high-energy impacts creating a molten surface on the infant Earth. According to this theory, water was brought to the world’s oceans thanks to icy comets, trans-Neptunian objects or water-rich meteoroids (protoplanets) from the outer reaches of the main asteroid belt colliding with the Earth.

However, more recent research conducted by the Woods Hole Oceanographic Institution (WHOI) in Woods Hole, Massachusetts, has pushed the date of these origins back further. According to this new study, the world’s oceans also date back 4.6 billion years, when all the worlds of the inner Solar System were still forming.

This conclusion was reached by examining meteorites thought to have formed at different times in the history of the Solar System. Carbonaceous chondrite, the oldest meteorites that have been dated to the very earliest days of the Solar System, were found to have the same chemistry as those originating from protoplanets like Vesta. This includes a significance presence of water.

These meteorites are dated to the same epoch in which water was believed to have formed on Earth – some 11 million years after the formation of the Solar System. In short, it now appears that meteorites were depositing water on Earth in its earliest days.

While not ruling out the possibility that some of the water that covers 71 percent of Earth today may have arrived later, these findings suggest that there was enough already here for life to have begun earlier than thought.

More information: water.usgs.gov/edu/earthhowmuch.html

Note : The above story is based on materials provided by Universe Today.

Dinosaur breathing study shows that noses enhanced smelling and cooled brain

Airflow modeled through the nasal cavity of the Cretaceous pachycephalosaur Stegoceras based on restoration of nasal soft tissues and Computation Fluid Dynamics of nasal airflow. This is the first study to analytically model nasal airflow in any extinct animal. A very general key finding was that comparative anatomy can be combined with engineering to restore the nasal physiology of extinct species. Courtesy of WitmerLab at Ohio University.

It’s been millions of years since T. rex took its last breath, but a team led by Ohio University scientists is breathing life back into dinosaurs using high-powered computer simulations to model airflow through dinosaur snouts. The research has important implications for how dinosaurs used their noses to not only breathe but to enhance the sense of smell and cool their brains.
“Dinosaurs were pretty ‘nosy’ animals,” said Ohio University doctoral student Jason Bourke, lead author of the new study published today in the Anatomical Record. “Figuring out what’s going on in their complicated snouts is challenging because noses have so many different functions. And it doesn’t help that all the delicate soft tissues rotted away millions of years ago.”

To restore what time had stripped away, the team turned to the modern-day relatives of dinosaurs—birds, crocodiles and lizards—to provide clues. “We’ll do whatever it takes,” said Lawrence Witmer, professor in the Ohio University Heritage College of Osteopathic Medicine and principal investigator on the National Science Foundation’s Visible Interactive Dinosaur Project, which funded much of the research. “We did lots of dissections, blood-vessel injections and CT scanning, but a major new tool was 3D computer simulation of airflow.”

Bourke drew from a branch of engineering called computational fluid dynamics, an approach commonly used in the aerospace industry and medicine, to model how air flowed through the noses of modern-day dinosaur relatives such as ostriches and alligators. “Once we got a handle on how animals today breathe,” Bourke said, “the tricky part was finding a good candidate among dinosaurs to test our methods.”

The dinosaurs that best fit the bill were the pachycephalosaurs, or “pachys,” a group of plant-eating dinosaurs best known for the several-inch-thick bone on the tops of their skulls which is thought to have served both as a visual display and as protection for head-butting behaviors like those of modern-day rams. It turns out that building all that extra skull bone resulted in ossifying soft tissues in other areas of the body—such as the nose.

“When we cleaned up the fossil skull of Sphaerotholus, a pachy from North Dakota, we didn’t expect to see these delicate scrolls of bone in the nasal region. We knew they must be nasal turbinates,” said Emma Schachner, a co-author on the study from Louisiana State University who, along with Tyler Lyson of the Denver Museum of Nature and Science, studied some of the fossil specimens used in the study. Similar structures were found in a different pachy species from Canada called Stegoceras by co-author Phil Bell from the University of New England in Australia.

The first nasal turbinates to be discovered were in the back part of the nasal cavity, called the olfactory chamber, where smelling takes place. Work by Witmer and Ohio University researcher Ryan Ridgely on CT scans of Stegoceras showed that the olfactory region of the brain was quite large, which, along with the large olfactory turbinates, suggested that Stegoceras had a good sense of smell.

But when Bourke ran his airflow simulation analyses, the inspired air bypassed the olfactory chamber. “It made no sense,” Bourke said. “Stegoceras obviously had a pretty decent sense of smell, but the odors weren’t reaching where they needed to go. We obviously were missing a piece of the puzzle.”

That missing puzzle piece was hinted at by a long bony ridge on the wall of the front of the nasal cavity. In the modern-day relatives of dinosaurs, cartilaginous nasal turbinates often attach to such ridges, suggesting to the team that pachys may have had turbinates in the front, respiratory part of the nasal cavity.

When Bourke digitally inserted respiratory turbinates of different shapes—whether it was the scrolled turbinate of a turkey or the branched turbinate of an ostrich—the computer airflow simulations started to make more sense.

“Some of the restored airflow patterns now carried odors to the olfactory region,” said Bourke. “We don’t really know what the exact shape of the respiratory turbinate was in Stegoceras, but we know some kind of baffle had to be there. We have the smoking gun of the bony ridge on the fossil, and the airflow analyses show that attaching some kind of turbinate produced the only airflow that made any real biological sense.”

Why have turbinates at all? Some scientists had previously suggested that warm-blooded animals such as birds and mammals have turbinates to act like condensers to save water that might have been lost during exhalation. That may be true in some cases, but this new research suggests that turbinates also have important functions as baffles to direct air to the olfactory region. But they might also play another critical role—cooling the brain.

Study co-author Ruger Porter, another Ohio University doctoral student, has been studying the pattern of blood flow in pachycephalosaurs and other dinosaurs, as well as their modern-day relatives. “The fossil evidence suggests that Stegoceras was basically similar to an ostrich or an alligator,” Porter said. “Hot arterial blood from the body was cooled as it passed over the respiratory turbinates, and then that cooled venous blood returned to the brain. It may not have been much of a brain, but you don’t want it cooked!”

Now that Bourke and his team have worked out nasal airflow in the “easy case” of Stegoceras, the team is turning its attention to trickier dinosaur cases, such the crazy-straw airways of armored ankylosaurs and duckbilled hadrosaurs.

The research was funded by National Science Foundation grants to Witmer and Ridgely and a fellowship to Bourke, as well as by the Ohio University Heritage College of Osteopathic Medicine.

Video:

Animation of simulated airflow in the Cretaceous pachycephalosaurid dinosaur Stegoceras (UALVP 2) based on different models of restored nasal soft tissues. In the absence of any restored soft tissues, modeled airflow bypasses the olfactory region, which is not realistic. By modeling a respiratory turbinate (in this case, an ostrich-like branched concha) attaching to the preserved bony ridge, realistic olfactory airflow is modeled. It’s also likely that the nasal structures functioned to cool blood that was destined for the brain region. This is largely the work of Jason Bourke (Ohio University) to accompany an article published in the Anatomical Record (2014) by Bourke, Porter, Ridgely, Lyson, Schachner, Bell, and Witmer. Research supported in part by the NSF-funded Visible Interactive Dinosaur project, WitmerLab at Ohio University.
Animation of simulated airflow in the Cretaceous pachycephalosaurid dinosaur Stegoceras (UALVP 2) based on different models of restored nasal soft tissues. This video is largely the work of Jason Bourke (Ohio University) and is an AR WOW video (http://bcove.me/k1si0ck1)  to accompany an article published in the Anatomical Record (2014) by Bourke, Porter, Ridgely, Lyson, Schachner, Bell, and Witmer. Research supported in part by the NSF-funded Visible Interactive Dinosaur project, WitmerLab at Ohio University.

Reference :
A technical article was published on 14 October 2014 in the Anatomical Record.

Note : The above story is based on materials provided by Ohio University.

American mastodons made warm Arctic, subarctic temporary home 125,000 years ago

This illustration shows a reconstruction of an American mastodon (Mammut americanum), top. Below is a comparison between an American mastodon (left) and a woolly mammoth. Credit: © George

Existing age estimates of American mastodon fossils indicate that these extinct relatives of elephants lived in the Arctic and Subarctic when the area was covered by ice caps—a chronology that is at odds with what scientists know about the massive animals’ preferred habitat: forests and wetlands abundant with leafy food.
In a paper published this week in the Proceedings of the National Academy of Sciences, an international team of researchers is revising fossil age estimates based on new radiocarbon dates and suggesting that the Arctic and Subarctic were only temporary homes to mastodons when the climate was warm. The new findings also indicate that mastodons suffered local extinction several tens of millennia before either human colonization—the earliest estimate of which is between 13,000 and 14,000 years ago—or the onset of climate changes at the end of the ice age about 10,000 years ago, when they were among 70 species of mammals to disappear in North America.

“Scientists have been trying to piece together information on these extinctions for decades,” said Ross MacPhee, a curator in the Department of Mammalogy at the American Museum of Natural History and a co-author on the paper. “Was is the result of over-hunting by early people in North America? Was it the rapid global warming at the end of the ice age? Did all of these big mammals go out in one dramatic die-off, or were they paced over time and due to a complex set of factors?”

Over the course of the late Pleistocene, between about 10,000 and 125,000 years ago, the American mastodon (Mammut americanum) became widespread and occupied many parts of continental North America as well as peripheral locations like the tropics of Honduras and the Arctic coast of Alaska. Mastodons were browsing specialists that relied on woody plants and lived in coniferous or mixed woodlands with lowland swamps.

“Mastodon teeth were effective at stripping and crushing twigs, leaves, and stems from shrubs and trees. So it would seem unlikely that they were able to survive in the ice-covered regions of Alaska and Yukon during the last full-glacial period, as previous fossil dating has suggested,” said Grant Zazula, a paleontologist in the Yukon Palaeontology Program and lead author on the new work.

The research team used two different types of precise radiocarbon dating on a collection of 36 fossil teeth and bones of American mastodons from Alaska and Yukon, the region known as eastern Beringia. The dating methods, performed at Oxford University and the University of California, Irvine, are designed to only target material from bone collagen, not accompanying “slop,” including preparation varnish and glues that were used many years ago to strengthen the specimens.

All of the fossils were found to be older than previously thought, with most surpassing 50,000 years, the effective limit of radiocarbon dating. When taking mastodon habitat preferences and other ecological and geological information into account, the results indicate that mastodons probably only lived in the Arctic and Subarctic for a limited time around 125,000 years ago, when forests and wetlands were established and the temperatures were as warm as they are today.

“The residency of mastodons in the north did not last long,” Zazula said. “The return to cold, dry glacial conditions along with the advance of continental glaciers around 75,000 years ago effectively wiped out their habitats. Mastodons disappeared from Beringia, and their populations became displaced to areas much farther to the south, where they ultimately suffered complete extinction about 10,000 years ago.”

The work has several implications. Researchers know that giant ground sloths, American camels, and giant beavers made the migration as well, but they are still investigating what other groups of animals might have followed this course. The new report also suggests that humans could not have been involved in the local extinction of mastodons in the north 75,000 years ago as they had not yet crossed the Bering Isthmus from Asia.

“We’re not saying that humans were uninvolved in the megafauna’s last stand 10,000 years ago. But by that time, whatever the mastodon population was down to, their range had shrunken mostly to the Great Lakes region,” MacPhee said. “That’s a very different scenario from saying the human depredations caused universal loss of mastodons across their entire range within the space of a few hundred years, which is the conventional view.”

Reference:
American mastodon extirpation in the Arctic and Subarctic predates human colonization and terminal Pleistocene climate change, PNAS, www.pnas.org/cgi/doi/10.1073/pnas.1416072111

Note : The above story is based on materials provided by American Museum of Natural History.

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