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Magnetometer

National Museum of American History
This type of unusually small magnetometer was designed by Emile Brunner in Paris in the 1880s and widely used by the French Magnetic Survey. This example is marked "Chasselon Paris No 42" and "USC & CS No. 21." It was made by Victor Chasselon around 1900, and belonged to the U.S. Coast and Geodetic Survey. After finding impurities in its brass, the Survey lent this instrument to the Carnegie Institution of Washington, and then to C. K. Edmunds, president of the Canton Christian College in China. Ref: E. Mascart, Traité de Magnétism Terrestre (Paris, 1900), pp. 211-214. Daniel Hazard, "Results of Magnetic Dip and Intensity Observations," Report of the Superintendent of the United States Coast and Geodetic Survey Showing the Progress of the Work from July 1, 1901, to June 30, 1902, Appendix No. 6, p. 350. Carnegie Institution of Washington. Department of Terrestrial Magnetism. Land Magnetic Observations, 1905-1910 (Washington, D.C., 1912), p. 6.

Young Walrus Teeth (3)

NMNH - Anthropology Dept.
Illus. p. 255 in Turner, Lucien M., Scott A. Heyes, and K. M. Helgen. 2014. Mammals of Ungava & Labrador: the 1882-1884 fieldnotes of Lucien M. Turner together with Inuit and Innu knowledge. Identified there: "Three juvenile walrus tusks. In Turner's manuscript (1887a: 120), he describes these walrus tusks as being "trophies, and also serve as material from which to fashion small articles". In his description of the tusks, he states: "Various portions of the teeth of the marine and terrestrial mammals are used to form many articles which, in the absence of metals, wood and stone have either too great brittleness or else soft and easily worn to withstand the pressure or shock to which the object subjected. The great size of the walrus tusk enables the Innuit to fashion innumerable objects from it while for smaller affairs the teeth of other mammals are equally suitable. In the absence of metal with which to shape the ivory sharp edged stones cut into shape and rough grained stones rub it to the required thickness.""

Detector, Electroscope, V. Hess

National Air and Space Museum
This is one of three original electroscopes used by the Austrian scientist Victor Hess during his balloon ascensions to measure ionizing radiation in the atmosphere in the period from 1911 to 1913. This instrument is a version of a commercial model of a Wulff electroscope especially modified by its manufacturer, Günther & Tegetmeyer (mfr. number 4760), to take into account operating under reduced pressure at high altitudes. Data collected by Hess led him to the conclusion that the radiation was of extra-terrestrial origin. He was awarded the Nobel Prize in 1936 for this discovery of what came to be known as cosmic rays. Hess immigrated to the U.S. in 1938 where he became a professor at Fordham University. The electroscope was donated to NASM by Fordham in 1990. It is now on display in the Explore the Universe gallery.

Global patterns in leaf C-13 discrimination and implications for studies of past and future climate

Smithsonian Libraries
Fractionation of carbon isotopes by plants during CO2 uptake and fixation (Delta(leaf)) varies with environmental conditions, but quantitative patterns of Delta(leaf) across environmental gradients at the global scale are lacking. This impedes interpretation of variability in ancient terrestrial organic matter, which encodes climatic and ecological signals. To address this problem, we converted 3,310 published leaf Alpha values into mean Delta(leaf) values for 334 woody plant species at 105 locations (yielding 570 species-site combinations) representing a wide range of environmental conditions. Our analyses reveal a strong positive correlation between Delta(leaf) and mean annual precipitation (MAP; R-2 = 0.55), mirroring global trends in gross primary production and indicating stomatal constraints on leaf gas-exchange, mediated by water supply, are the dominant control of Delta(leaf) at large spatial scales. Independent of MAP, we show a lesser, negative effect of altitude on Delta(leaf) and minor effects of temperature and latitude. After accounting for these factors, mean Delta(leaf) of evergreen gymnosperms is lower (by 1-2.7%) than for other woody plant functional types (PFT), likely due to greater leaf-level water-use efficiency. Together, environmental and PFT effects contribute to differences in mean Delta(leaf) of up to 6% between biomes. Coupling geologic indicators of ancient precipitation and PFT (or biome) with modern Delta(leaf) patterns has potential to yield more robust reconstructions of atmospheric delta C-13 values, leading to better constraints on past greenhouse-gas perturbations. Accordingly, we estimate a 4.6% decline in the delta C-13 of atmospheric CO2 at the onset of the Paleocene-Eocene Thermal Maximum, an abrupt global warming event similar to 55.8 Ma.

Endangered Kiwi Chick Hatched at the Smithsonian Conservation Biology Institute

National Zoo
May 31, 2016—For the first time, an egg laid by a female brown kiwi at the Smithsonian Conservation Biology Institute (SCBI) in Front Royal, Va., hatched May 10. The chick is the first for parents Ngati Hine Rua (female) and Ngati Hine Tahi (male). SCBI has previously hatched eggs originally laid at other zoos. Keepers will not know the sex of the chick for several weeks. Ngati Hine Rua and Ngati Hine Tahi were given to SCBI as a gift from the government of New Zealand in 2010 after receiving a Maori blessing. Kiwi are sacred to the Maori people. The gift was the first time any kiwi had left New Zealand in 20 years. The Smithsonian’s National Zoo was the first outside of New Zealand to successfully breed kiwi in 1975. Feathers from kiwi at the Zoo and SCBI are repatriated to New Zealand and returned to the Maori people. After Ngati Hine Rua laid the egg, Iwi, another male living at SCBI, incubated it for 30 days before keepers moved the egg to a meticulously climate-controlled incubator where it finished developing. Kiwi do not care for their chicks, which are capable of caring for themselves at birth. After hatching, the chick was moved to an incubator especially for newborn chicks. The chick appears to be healthy and doing well. Kiwi, flightless birds similar in size to chickens, lay the largest egg-to-body-weight ratio of any bird. A kiwi egg is about 20 percent of the female’s size. Kiwi live in mated pairs and generally mate for life. The pair will defend a territory, which includes their nest. After females lay their eggs, they leave the egg with the male to incubate by himself. A chick will stay in its parents’ territory for up to one year, but is able to hunt and fend for itself from birth. The nocturnal kiwi is endangered due to predators introduced to New Zealand by humans. Kiwi evolved without terrestrial mammal predators. Their biggest threats are dogs, cats and stoats introduced by humans. The Smithsonian Conservation Biology Institute plays a leading role in the Smithsonian’s global efforts to save wildlife species from extinction and train future generations of conservationists. SCBI spearheads research programs at its headquarters in Front Royal, Va., the Smithsonian’s National Zoo in Washington, D.C., and at field research stations and training sites worldwide. SCBI scientists tackle some of today’s most complex conservation challenges by applying and sharing what they learn about animal behavior and reproduction, ecology, genetics, migration and conservation sustainability.

How Did Whales Evolve?

Smithsonian Magazine

What springs to mind when you think of a whale? Blubber, blowholes and flukes are among the hallmarks of the roughly 80 species of cetaceans (whales, dolphins and porpoises) alive today. But, because they are mammals, we know that they must have evolved from land-dwelling ancestors.

About 375 million years ago, the first tetrapods—vertebrates with arms and legs—pushed themselves out of the swamps and began to live on land. This major evolutionary transition set the stage for all subsequent groups of land-dwelling vertebrates, including a diverse lineage called synapsids, which originated about 306 million years ago. Though these creatures, such as Dimetrodon, looked like reptiles, they were actually the archaic precursors of mammals.

By the time the first mammals evolved 200 million years ago, however, dinosaurs were the dominant vertebrates. Mammals diversified in the shadow of the great archosaurs, and they remained fairly small and secretive until the non-avian dinosaurs were wiped out by a mass extinction 65 million years ago. This global catastrophe cleared the way for a major radiation of mammals. It was only about 10 million years after this extinction—and more than 250 million years since the earliest tetrapods crawled out onto land—that the first whales evolved. These earliest cetaceans were not like the whales we know today, and only recently have paleontologists been able to recognize them.

For more than a century, our knowledge of the whale fossil record was so sparse that no one could be certain what the ancestors of whales looked like. Now the tide has turned. In the space of just three decades, a flood of new fossils has filled in the gaps in our knowledge to turn the origin of whales into one of the best-documented examples of large-scale evolutionary change in the fossil record. These ancestral creatures were stranger than anyone ever expected. There was no straight-line march of terrestrial mammals leading up to fully aquatic whales, but an evolutionary riot of amphibious cetaceans that walked and swam along rivers, estuaries and the coasts of prehistoric Asia. As strange as modern whales are, their fossil predecessors were even stranger.

Pioneers who cleared land in Alabama and Arkansas frequently found enormous round bones. Some settlers used them as fireplace hearths; others propped up fences with the bones or used them as cornerstones; slaves used the bones as pillows. The bones were so numerous that in some fields they were destroyed because they interfered with cultivating the land.

In 1832, a hill collapsed on the Arkansas property of Judge H. Bry and exposed a long sequence of 28 of the circular bones. He thought they might be of scientific interest and sent a package to the American Philosophical Society in Philadelphia. No one quite knew what to make of them. Some of the sediment attached to the bone contained small shells that showed that the large creature had once lived in an ancient sea, but little more could be said with any certainty.

Bry’s donation was soon matched, and even exceeded, by that of Judge John Creagh from Alabama. He had found vertebrae and other fragments while blasting on his property and also sent off a few samples to the Philadelphia society. Richard Harlan reviewed the fossils, which were unlike any he had seen before. He asked for more bones, and Creagh soon sent parts of the skull, jaws, limbs, ribs, and backbone of the enigmatic creature. Given that both Creagh and Bry said they had seen intact vertebral columns in excess of 100 feet in length, the living creature must have been one of the largest vertebrates to have ever lived. But what kind of animal was it?

Harlan thought the bones were most similar to those of extinct marine reptiles such as the long-necked plesiosaurs and streamlined ichthyosaurs. He tentatively assigned it the name Basilosaurus. He wasn’t certain, though. The jaw contained teeth that differed in size and shape, a characteristic of mammals but not most reptiles. Why did the largest fossil reptile that ever lived have mammal-like teeth?

Harlan traveled to London in 1839 to present Basilosaurus to some of the leading paleontologists and anatomists of the day. Richard Owen, a rising star in the academic community, carefully scrutinized every bone, and he even received permission to slice into the teeth to study their microscopic structure. His attention to such tiny details ultimately settled the identification of the sea monster. Basilosaurus did share some traits with marine reptiles, but this was only a superficial case of convergence—of animals in the same habitat evolving similar traits—because both types of creature had lived in the sea. The overall constellation of traits, including double-rooted teeth, unquestionably identified Basilosaurus as a mammal.

Image by DK Limited / Corbis. After inspecting vertebrae and other fragments found in Alabama, Richard Harlan of the American Philosophical Society in Philadelphia thought the bones were most similar to those of extinct marine reptiles. He tentatively assigned it the name Basilosaurus. Pictured is a 3D model of a Basilosaurus. (original image)

Image by From Fowler, O.S. 1846. The American Phrenological Journal and Miscellany, Vol. 8. New York: Fowler & Wells.. An illustration of German-born fossil collector Albert Koch's "Hydrarchos" as it appeared on display. (original image)

A few years later, a scientist handling a different specimen with his colleagues pulled out a bone from the skull, dropped it, and it shattered on the floor. When the unnerved scientists gathered the fragments, they noticed that the bone now revealed the inner ear. There was only one other kind of creature with an inner ear that matched: a whale.

Not long after the true identity of Basilosaurus was resolved, Charles Darwin’s theory of evolution by means of natural selection raised questions about how whales evolved. The fossil record was so sparse that no definite determination could be made, but in a thought experiment included in On the Origin of Species, Darwin speculated about how natural selection might create a whale-like creature over time:

In North America the black bear was seen by [the explorer Samuel] Hearne swimming for hours with widely open mouth, thus catching, like a whale, insects in the water. Even in so extreme a case as this, if the supply of insects were constant, and if better adapted competitors did not already exist in the country, I can see no difficulty in a race of bears being rendered, by natural selection, more and more aquatic in their structure and habits, with larger and larger mouths, till a creature was produced as monstrous as a whale.

Darwin was widely ridiculed for this passage. Critics took it to mean he was proposing that bears were direct ancestors of whales. Darwin had done no such thing, but the jeering caused him to modify the passage in subsequent editions of the book. But while preparing the sixth edition, he decided to include a small note about Basilosaurus. Writing to his staunch advocate T.H. Huxley in 1871, Darwin asked whether the ancient whale might represent a transitional form. Huxley replied that there could be little doubt that Basilosaurus provided clues as to the ancestry of whales.

Huxley thought that Basilosaurus at least represented the type of animal that linked whales to their terrestrial ancestors. If this was true, then it seemed probable that whales had evolved from some sort of terrestrial carnivorous mammal. Another extinct whale called Squalodon, a fossil dolphin with a wicked smile full of triangular teeth, similarly hinted that whales had evolved from meat-eating ancestors. Like Basilosaurus, though, Squalodon was fully aquatic and provided few clues as to the specific stock from which whales arose. Together these fossil whales hung in a kind of scientific limbo, waiting for some future discovery to connect them with their land-dwelling ancestors.

In the meantime, scientists speculated about what the ancestors of whales might have been like. The anatomist William Henry Flower pointed out that seals and sea lions use their limbs to propel themselves through the water while whales lost their hind limbs and swam by oscillations of their tail. He could not imagine that early cetaceans used their limbs to swim and then switched to tail-only propulsion at some later point. The semi-aquatic otters and beavers, he claimed, were better alternative models for the earliest terrestrial ancestors of whales. If the early ancestors of whales had large, broad tails, that could explain why they evolved such a unique mode of swimming.

Contrary to Huxley’s carnivore hypothesis, Flower thought that ungulates, or hoofed mammals, shared some intriguing skeletal similarities with whales. The skull of Basilosaurus had more in common with ancient “pig-like Ungulates” than seals, thus giving the common name for the porpoise, “sea-hog,” a ring of truth. If ancient omnivorous ungulates could eventually be found, Flower reasoned, it would be likely that at least some would be good candidates for early whale ancestors. He envisioned a hypothetical cetacean ancestor easing itself into the shallows:

We may conclude by picturing to ourselves some primitive generalized, marsh-haunting animals with scanty covering of hair like the modern hippopotamus, but with broad, swimming tails and short limbs, omnivorous in their mode of feeding, probably combining water plants with mussels, worms, and freshwater crustaceans, gradually becoming more and more adapted to fill the void place ready for them on the aquatic side of the borderland on which they dwelt, and so by degree being modified into dolphin-like creatures inhabiting lakes and rivers, and ultimately finding their way into the ocean.

The fossil remains of such a creature remained elusive. By the turn of the 20th century the oldest fossil whales were still represented by Basilosaurus and similar forms like Dorudon and Protocetus, all of which were fully aquatic—there were no fossils to bridge the gap from land to sea. As E.D. Cope admitted in an 1890 review of whales: “The order Cetacea is one of those of whose origin we have no definite knowledge.” This state of affairs continued for decades.

While analyzing the relationships of ancient meat-eating mammals in 1966, however, the evolutionary biologist Leigh Van Valen was struck by the similarities between an extinct group of land-dwelling carnivores called mesonychids and the earliest known whales. Often called “wolves with hooves,” mesonychids were medium- to large-sized predators with long, toothy snouts and toes tipped with hooves rather than sharp claws. They were major predators in the Northern Hemisphere from shortly after the demise of the dinosaurs until about 30 million years ago, and the shape of their teeth resembled those of whales like Protocetus.

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Van Valen hypothesized that some mesonychids may have been marsh dwellers, “mollusk eaters that caught an occasional fish, the broadened phalanges [finger and toe bones] aiding them on damp surfaces.” A population of mesonychids in a marshy habitat might have been enticed into the water by seafood. Once they had begun swimming for their supper, succeeding generations would become more and more aquatically adapted until something “as monstrous as a whale” evolved.

A startling discovery made in the arid sands of Pakistan announced by University of Michigan paleontologists Philip Gingerich and Donald Russell in 1981 finally delivered the transitional form scientists had been hoping for. In freshwater sediments dating to about 53 million years ago, the researchers recovered the fossils of an animal they called Pakicetus inachus. Little more than the back of the animal’s skull had been recovered, but it possessed a feature that unmistakably connected it to cetaceans.

Cetaceans, like many other mammals, have ear bones enclosed in a dome of bone on the underside of their skulls called the auditory bulla. Where whales differ is that the margin of the dome closest to the midline of the skull, called the involucrum, is extremely thick, dense, and highly mineralized. This condition is called pachyosteosclerosis, and whales are the only mammals known to have such a heavily thickened involucrum. The skull of Pakicetus exhibited just this condition.

Even better, two jaw fragments showed that the teeth of Pakicetus were very similar to those of mesonychids. It appeared that Van Valen had been right, and Pakicetus was just the sort of marsh-dwelling creature he had envisioned. The fact that it was found in freshwater deposits and did not have specializations of the inner ear for underwater hearing showed that it was still very early in the aquatic transition, and Gingerich and Russell thought of Pakicetus as “an amphibious intermediate stage in the transition of whales from land to sea,” though they added the caveat that “Postcranial remains [bones other than the skull] will provide the best test of this hypothesis.” The scientists had every reason to be cautious, but the fact that a transitional whale had been found was so stupendous that full-body reconstructions of Pakicetus appeared in books, magazines and on television. It was presented as a stumpy-legged, seal-like creature, an animal caught between worlds.

Throughout the 1990s, the skeletons of more or less aquatically adapted ancient whales, or archaeocetes, were discovered at a dizzying pace. With this new context, however, the stubby, seal-like form for Pakicetus depicted in so many places began to make less and less sense. Then, in 2001, J.G.M. Thewissen and colleagues described the long-sought skeleton (as opposed to just the skull) of Pakicetus attocki. It was a wolf-like animal, not the slick, seal-like animal that had originally been envisioned. Together with other recently discovered genera like HimalayacetusAmbulocetusRemingtonocetusKutchicetusRodhocetus and Maiacetus, it fits snugly within a collection of archaeocetes that exquisitely document an evolutionary radiation of early whales. Though not a series of direct ancestors and descendants, each genus represents a particular stage of whale evolution. Together they illustrate how the entire transition took place.

The earliest known archaeocetes were creatures like the 53-million-year-old Pakicetus and the slightly older Himalayacetus. They looked as if they would have been more at home on land than in the water, and they probably got around lakes and rivers by doing the doggie paddle. A million years later lived Ambulocetus, an early whale with a crocodile-like skull and large webbed feet. The long-snouted and otter-like remingtonocetids appeared next, including small forms like the 46-million-year-old Kutchicetus. These early whales lived throughout near-shore environments, from saltwater marshes to the shallow sea.

Living at about the same time as the remingtonocetids was another group of even more aquatically adapted whales, the protocetids. These forms, like Rodhocetus, were nearly entirely aquatic, and some later protocetids, like Protocetus and Georgiacetus, were almost certainly living their entire lives in the sea. This shift allowed the fully aquatic whales to expand their ranges to the shores of other continents and diversify, and the sleeker basilosaurids like DorudonBasilosaurus and Zygorhiza populated the warm seas of the late Eocene. These forms eventually died out, but not before giving rise to the early representatives of the two groups of whales alive today, the toothed whales and the baleen whales. The early representatives of these groups appeared about 33 million years ago and ultimately gave rise to forms as diverse as the Yangtze River dolphin and the gigantic blue whale.

Studies coming out of the field of molecular biology conflicted with the conclusion of the paleontologists that whales had evolved from mesonychids, however. When the genes and amino acid sequences of living whales were compared with those of other mammals, the results often showed that whales were most closely related to artiodactyls—even-toed ungulates like antelope, pigs, and deer. Even more surprising was that comparisons of these proteins used to determine evolutionary relationships often placed whales within the Artiodactyla as the closest living relatives to hippos.

This conflict between the paleontological and molecular hypotheses seemed intractable. Mesonychids could not be studied by molecular biologists because they were extinct, and no skeletal features had been found to conclusively link the archaeocetes to ancient artiodactyls. Which were more reliable, teeth or genes? But the conflict was not without hope of resolution. Many of the skeletons of the earliest archaeocetes were extremely fragmentary, and they were often missing the bones of the ankle and foot. One particular ankle bone, the astragalus, had the potential to settle the debate. In artiodactyls this bone has an immediately recognizable “double pulley” shape, a characteristic mesonychids did not share. If the astragalus of an early archaeocete could be found it would provide an important test for both hypotheses.

In 2001, archaeocetes possessing this bone were finally described, and the results were unmistakable. Archaeocetes had a “double-pulley” astragalus, confirming that cetaceans had evolved from artiodactyls. Mesonychids were not the ancestors of whales, and hippos are now known to be the closest living relatives to whales.

Recently scientists determined which group of prehistoric artiodactyls gave rise to whales. In 2007, Thewissen and other collaborators announced that Indohyus, a small deer-like mammal belonging to a group of extinct artiodactyls called raoellids, was the closest known relative to whales. While preparing the underside of the skull of Indohyus, a student in Thewissen’s lab broke off the section covering the inner ear. It was thick and highly mineralized, just like the bone in whale ears. Study of the rest of the skeleton also revealed that Indohyus had bones marked by a similar kind of thickening, an adaptation shared by mammals that spend a lot of time in the water. When the fossil data was combined with genetic data by Jonathan Geisler and Jennifer Theodor in 2009, a new whale family tree came to light. Raoellids like Indohyus were the closest relatives to whales, with hippos being the next closest relatives to both groups combined. At last, whales could be firmly rooted in the mammal evolutionary tree.

Adapted from Written in Stone: Evolution, the Fossil Record, and Our Place in Nature, by Brian Switek. Copyright 2010. With the permission of the publisher, Bellevue Literary Press.

Massive Volcanic Eruptions Triggered Earth’s "Great Dying"

Smithsonian Magazine

The world’s worst mass extinction has been a great whodunit for decades. Some 252 million years ago, 75 percent of land species and 90 percent of those in the oceans disappeared. But what caused trilobites, Eurypterid “sea scorpions” and all those other species to go extinct?

Scientists had long suspected that massive releases of magma from the Siberian Traps played a key role, and now they have the best evidence yet that the ancient volcanic activity most likely triggered the Great Dying.

The key to solving this puzzle was figuring out the timing of the two events. Early studies had estimated that the mass extinction and the Siberian Traps eruptions happened within a few million years of each other. But there was so much uncertainty in the dates for the two events that no one could say for certain which happened first.

“For magmatism to be a plausible trigger, we must be able to assert outside the uncertainty on the dates that it preceded [the] mass extinction,” says Seth Burgess, a post-doc at the U.S. Geological Survey who completed this research while he was a graduate student at MIT. “Simply put, if magmatism began after the onset of mass extinction, then magmatism isn’t the cause.”

Burgess and his colleagues nailed down the timing of the mass extinction last year by determining the ages of rocks in China that had been laid down before and after the epic die-off. They found that the event occurred within a 60,000-year period 252 million years ago.

The new study, published today in Science Advances, focused on the other half of the equation, the Siberian Traps. This eruptive event brought some 700,000 cubic miles of rock and lava to the surface, the remains of which cover an area of Siberia equivalent to all of Western Europe.

Burgess and Samuel Bowring of MIT used uranium-lead dating—the same technique employed in their previous study—to provide a timeline of the eruptions. They calculate that magmatism began about 300,000 years before the mass extinction and continued for some 500,000 years after.

“We show that magmatism is a plausible trigger” for the Great Dying, Burgess says. A big question, though, is why the die-off didn’t start until hundreds of thousands of years after the eruptions began. It could be that the planet reached a tipping point only after a critical volume of magma had erupted, Burgess says. Or only small amounts of magma erupted until right before the mass extinction began.

Answering this question may be tied to figuring out exactly how the magmatism caused such devastation to the planet’s life.

“We’ve now got a pretty good handle on the ‘when,’ but details of the ‘how’ are still uncertain,” Burgess says. For the oceans, at least, scientists have a good working theory: In addition to rock and lava, the Siberian Traps released huge amounts of carbon dioxide into the atmosphere. Earlier this year, researchers presented evidence that this caused an abrupt increase in ocean acidification that would have driven many species out of existence.

What caused the terrestrial creatures to go extinct, though, is more of an enigma. “There are quite a few theories,” Burgess notes, such as hot atmospheric temperatures, huge fires and rain as acidic as lemon juice.

Mineral evolution

Smithsonian Libraries
The mineralogy of terrestrial planets evolves as a consequence of a range of physical, chemical, and biological processes. In pre-stellar molecular clouds, widely dispersed microscopic dust particles contain approximately a dozen refractory minerals that represent the starting point of planetary mineral evolution. Gravitational clumping into a protoplanetary disk, star formation, and the resultant heating in the stellar nebula produce primary refractory constituents of chondritic meteorites, including chondrules and calcium-aluminum inclusions, with ~60 different mineral phases. Subsequent aqueous and thermal alteration of chondrites, asteroidal accretion and differentiation, and the consequent formation of achondrites results in a mineralogical repertoire limited to ~250 different minerals found in unweathered meteorite samples. Following planetary accretion and differentiation, the initial mineral evolution of Earth's crust depended on a sequence of geochemical and petrologic processes, including volcanism and degassing, fractional crystallization, crystal settling, assimilation reactions, regional and contact metamorphism, plate tectonics, and associated large-scale fluid-rock interactions. These processes produced the first continents with their associated granitoids and pegmatites, hydrothermal ore deposits, metamorphic terrains, evaporites, and zones of surface weathering, and resulted in an estimated 1500 different mineral species. According to some origin-of-life scenarios, a planet must progress through at least some of these stages of chemical processing as a prerequisite for life. Biological processes began to affect Earth's surface mineralogy by the Eoarchean Era (~3.85-3.6 Ga), when large-scale surface mineral deposits, including banded iron formations, were precipitated under the influences of changing atmospheric and ocean chemistry. The Paleoproterozoic "Great Oxidation Event" (~2.2 to 2.0 Ga), when atmospheric oxygen may have risen to >1% of modern levels, and the Neoproterozoic increase in atmospheric oxygen, which followed several major glaciation events, ultimately gave rise to multicellular life and skeletal biomineralization and irreversibly transformed Earth's surface mineralogy. Biochemical processes may thus be responsible, directly or indirectly, for most of Earth's 4300 known mineral species. The stages of mineral evolution arise from three primary mechanisms: (1) the progressive separation and concentration of the elements from their original relatively uniform distribution in the pre-solar nebula; (2) an increase in range of intensive variables such as pressure, temperature, and the activities of H2O, CO2, and O2; and (3) the generation of far-from-equilibrium conditions by living systems. The sequential evolution of Earth's mineralogy from chondritic simplicity to Phanerozoic complexity introduces the dimension of geologic time to mineralogy and thus provides a dynamic alternate approach to framing, and to teaching, the mineral sciences.

How a Single Act of Evolution Nearly Wiped Out All Life on Earth

Smithsonian Magazine

Evolution giveth, and, 252 million years ago, evolution nearly tooketh away.

The power of natural selection and random mutations have, over time, created the amazing diversity of life on Earth, from the little lice that live on your lashes to the mighty blue whale. But, once, a single act of evolution—the transfer of two genes from one type of bacteria to one type of archaea—nearly wiped out all life on this planet, suggests a team of researchers in a new study.

Roughly 252 million years ago, the Permian-Triassic extinction, known as the Great Dying, saw 90 percent of marine life and 70 percent of terrestrial life snuffed out in a relative blink of an eye. The functional cause was a disruption of the planet's carbon cycle, which transfers carbon between air, sea and land and keeps a certain portion in long-term storage. Something—scientists don't know for sure—caused a burst of carbon to come out of storage. When it did, the temperature soared, the ocean acidified and life on Earth nearly collapsed.

Previously, scientists have tried to pin the shift in the carbon cycle and the ensuing extinction on everything from meteorites to volcanoes. Some scientists say the Great Dying happened all at once, while others suggest it happened in waves.

In the new study, led by geophysicist Daniel Rothman, the researchers noticed something important about the rate of the disruption. If the extinction had been caused by a meteorite or volcano, the changes likely would have come as a burst before slowly tapering off. But that's not what they saw. Instead, the disruption of the carbon cycle appeared to be exponential—growing faster and faster with time. To them this suggests one thing: rampant microbial growth.

Though we tend to think of evolution as a particular individual organism having a genetic mutation that works out, in microbes, evolution can also happen when microbes of different types trade genes.

The scientists posit that, around the time of the extinction, a type of archaea known as Methanosarcina gained two genes from a bacteria. These genes gave them the ability to eat the organic wastes that litter the sea floor. As they ate, the archaea would have pumped out methane gas—rushing carbon that had long been stored in the organic materials back into the water. Through a genetic analysis, the scientists calculated that Methanosarcina gained this ability some time from 200 to 280 million years ago.

Whether Rothman and colleagues' speculations pan out will be seen with time, but that this scenario is even plausible is a testament to the power of microbial evolution. From the onset of photosynthesis to outbreaks of disease and who knows what's next, it's a reminder that Earth is the microbes' world. We just live in it.

The Paleo Diet May Need a Rewrite, Ancient Humans Feasted on a Wide Variety of Plants

Smithsonian Magazine

The Paleo diet is a fad that claims to be based on what the human body was designed to eat—a pre-agriculture mix including meats, roots, fruits, vegetables and nuts. While it has its plusses and minuses, the big fault is that we really don’t know what the original paleo diet, which humans ate between 2.6 million years ago to about 12,000 years ago, looked like. Colin Barras at New Scientist reports that the “caveman” fascination with meat is often overemphasized because the bones of butchered animals tend to last a long time, while other materials have disintegrated.

But researchers at the Gesher Benot Ya’aqov archaeological site on Lake Hula in northern Israel have found a camp used by human ancestors which includes a whole menu of the plant-based foods that they would have sampled. The site, reports Barras, was likely inhabited by Homo erectus or a closely related human species and includes the remains of at least 55 edible plant species, including nuts, fruit seeds, roots, tubers, leaves and stems.

According to a press release, the site was covered by sediment from the Jordan River, which helped preserve the 9,000 bits of plant debris and seeds. Stone tools and animal bones found in the same layer of sediment as the plant debris allowed the researchers to associate the food remains with the shoreline’s prehistoric residents. The research appears in the Proceedings of the National Academy of Sciences.

The wide-variety of plant materials puts current veggie lovers to shame. “The modern human diet is clearly restricted when compared to the [early] hominin diet or even to the early farmers’ diet,” Naama Goren-Inbar archaeologist from the Institute of Archeology at the Hebrew University of Jerusalem and one of the study’s lead authors tells Barras. “It gives one a substantial element of security when particular sources become rare or absent.”

In fact, the wide variety of foods probably gave the early hominids the ability to find suitable food year-round. What’s more, Goren-Inbar says in the press release that the use of fire—the earliest evidence of which is also found at the site in recent years—gave the inhabitants more choices. “The use of fire is very important because a lot of the plants are toxic or inedible. Using fire, like roasting nuts and roots for example, allows the use of various parts of the plant and increases the diversity of the plant component of [their] diet, alongside aquatic and terrestrial fauna.”

Many of the snacks recorded at the site would be strange and unpalatable to us today. But some are familiar, reports Ilan Ben Zion at The Times of Israel, including a version of the water chestnut as well as grapes, raspberries, pears and almonds. One of the most abundant was the gorgon nut, which is still eaten like popcorn in India.

So how does the Lake Hula feast stack up to the modern Paleo diet? Researchers say that the residents of the site probably needed meat to stay healthy, but not as much as Fred Flintstone used to gobble. “We need plant-derived nutrients to survive – vitamin C and fibre, for example,” Amanda Harry of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, tells Barras. “Hominins were probably predominantly vegetarians.”

Editor's note, December 15, 2016: This piece has been updated to clarify that the modern Paleo diet also includes vegetables.

Cocconeis crebra Fleming

NMNH - Botany Dept.

Vulnerability and Resilience of Tropical Forest Species to Land-Use Change

Smithsonian Libraries
We provide a cross-taxon and historical analysis of what makes tropical forest species vulnerable to extinction. Several traits have been important for species survival in the recent and distant geological past, including seed dormancy and vegetative growth in plants, small body size in mammals, and vagility in insects. For major past catastrophes, such as the five mass extinction events, large range size and vagility or dispersal were key to species survival. Traits that make some species more vulnerable to extinction are consistent across time scales. Terrestrial organisms, particularly animals, are more extinction prone than marine organisms. Plants that persist through dramatic changes often reproduce vegetatively and possess mechanisms of die back. Synergistic interactions between current anthropogenic threats, such as logging, fire, hunting, pests and diseases, and climate change are frequent. Rising temperatures threaten all organisms, perhaps particularly tropical organisms adapted to small temperature ranges and isolated by distance from suitable future climates. Mutualist species and trophic specialists may also be more threatened because of such range-shift gaps. Phylogenetically specialized groups may be collectively more prone to extinction than generalists. Characterization of tropical forest species' vulnerability to anthropogenic change is constrained by complex interactions among threats and by both taxonomic and ecological impediments, including gross undersampling of biotas and poor understanding of the spatial patterns of taxa at all scales. Aportamos un análisis trans-taxón e histórico de lo que hace que las especies de bosques tropicales sean vulnerables a la extinción. Varios atributos han sido importantes para la supervivencia de especies en el pasado reciente y geológico, incluyendo la latencia de semillas y el crecimiento vegetativo en plantas, el tamaño corporal pequeño de mamíferos y la vagilidad en insectos. Para las mayores catástrofes del pasado, como los cinco eventos de extinción masiva, la extensión del rango y la vagilidad o dispersión fueron claves para la supervivencia de especies. Los atributos que hacen que algunas especies sean más vulnerables a la extinción son consistentes a través de las escalas de tiempo. Los organismos terrestres, particularmente animales, son más propensos a la extinción que los organismos marinos. Las plantas que persisten a través de cambios dramáticos a menudo se reproducen vegetativamente y poseen mecanismos de muerte regresiva. Las interacciones sinérgicas entre amenazas antropogénicas actuales, como explotación de madera, fuego, cacería, plagas y enfermedades y cambio climático son frecuentes. Las temperaturas crecientes amenazan a todos los organismos, quizás particularmente a organismos tropicales adaptados a rangos de temperatura pequeños y aislados por distancia de climas futuros adecuados. Las especies mutualistas y los especialistas tróficos pueden estar más amenazados debidos a tales discontinuidades en los cambios de rango. Los grupos filogenéticamente especializados colectivamente pueden ser más propensos a la extinción que los generalistas. La caracterización de la vulnerabilidad de las especies de bosques tropicales al cambio antropogénico está limitada por las complejas interacciones entre amenazas y tanto por impedimentos taxonómicos y ecológicos, incluyendo el muestreo incompletos de biotas y el pobre entendimiento de los patrones espaciales de taxa a todas las escalas.

Scientists Discover a New Species of Tapir; Locals Say, “We Told You!”

Smithsonian Magazine
People usually know what they're talking about when it comes to the animals that live in their own backyard. For years, however, scientists ignored locals in the Amazon who said there was not one but two species of tapir—a large mammal that slightly resembles a pig—roaming the forest, Mongabay reports. Now, science has caught up to what the locals knew all along. Authors of a recent research paper finally paid attention and discovered that a new species of tapir does indeed exist.

Four other species of tapirs are found in the Amazon and in Southeast Asia, but a new one hasn't been discovered since 1865. The new tapir, dubbed Tapirus kabomani, is the smallest of the bunch but still counts as one of the largest mammals found in South America.

Mongabay elaborates:

Found inhabiting open grasslands and forests in the southwest Amazon (the Brazilian states of Rondônia and Amazonas, as well as the Colombian department of Amazonas), the new species is regularly hunted by the Karitiana tribe who call it the "little black tapir." The new species is most similar to the Brazilian tapir (Tapirus terrestris), but sports darker hair and is significantly smaller: while a Brazilian tapir can weigh up to 320 kilograms (710 pounds), the Kabomani weighs-in around 110 kilograms (240 pounds). Given its relatively small size it likely won't be long till conservationists christen it the pygmy or dwarf tapir. It also has shorter legs, a distinctly-shaped skull, and a less prominent crest.

After noticing some discrepancies in tapir skull specimens about a decade ago, lead author Mario Cozzuol finally decided to investigate. He followed up on leads from locals about the "little black tapir," and they provided Cozzuol and his team with skulls and other materials for genetic analysis. Those tests, combined with field surveys, confirmed that this tapir was indeed a species unrecognized by the scientific community. "Local peoples have long recognized our new species, suggesting a key role for traditional knowledge in understanding the biodiversity of the region," Cozzuol concludes in his paper. 

Interestingly enough, it seems Theodore Roosevelt also listened to the native experts. A skull from an animal he hunted in 1912 matches up with the new species, Mongobay writes, and at the time Roosevelt commented that indigenous people told him it belonged to a "distinct kind" of tapir.

More from Smithsonian.com:

Killer Whales May Be Two Distinct Species
Meet the World's Newest Monkey Species  

This 36-Million-Year-Old Fossil Is a "Missing Link" in Whale Evolution

Smithsonian Magazine

About 50 million years ago, the earliest ancestors of whales slipped into the ocean. Generation after generation, the creatures slowly changed, losing their hind limbs and gaining flippers. A group of these early creatures, known as the basilosaurids, evolved into two broad groups of whales that are found today: the toothed whales, like modern sperm whales and orcas, and the filter-feeding baleen whales, like today's blue whales and humpbacks.

Molecular and genetic research suggests that this split took place roughly 38 to 39 million years ago, but until now no fossils of these early creatures had been found. But as Sarah McQuate reports for Nature, scientists have uncovered the oldest baleen-whale relative yet. And at 36.4 million years old, this this fossil fills in the gaps in whale evolution

As McQuate reports, the new species was excavated from Playa Media Luna in the Pisco Basin area of southern Peru and has been named Mystacodon selenensis. The creature was likely about 13-feet long, the length of a bottlenosed dolphin. But unlike modern baleen whales, which use plates made of keratin to screen krill and other small organisms out of the water, M. selenensis had teeth and likely sucked up small creatures like shrimp or squid off the bottom of the ocean floor.

That suction feeding technique links M. selenensis to older species and modern whales. “It perfectly matches what we would have expected as an intermediary step between ancestral basilosaurids and more derived mysticetes [baleen whales],” paleontologist Olivier Lambert of the Royal Belgian Institute of Natural Sciences and co-author of the paper in Current Biologysays in a press release. “This nicely demonstrates the predictive power of the theory of evolution.”

As Nicola Davis at The Guardian reports, the find also jibes with another whale fossil discovered, dubbed Alfred. That specimen dates back some 25 million years ago and was also a suction feeder, suggesting that it took a long time for modern baleen feeding to develop.

While the fossil bears out paleontologists' predictions, it did come with one big surprise: it had tiny hind limbs sticking out of its body, Davis reports. Lambert says that these tiny limbs had no real function—also known as vestigial organs. But the find upturned researchers' belief that whales completely lost their back limbs before the toothed and baleen whale ancestors split.

Paleontologists have been slow to put together the whale family tree, Lambert says, because they have been looking for fossils close to home in Europe and North America. But it turns out that much of the action in whale evolution took place in Antarctica, Peru, and India. Now that they are looking in the right places, they are finding more and more specimens.

That’s also a plus for evolutionary theory in general. “For a long time, Creationists took the evolution of whales as a favorite target to say that, 'Well, you say that whales come from a terrestrial ancestor, but you can't prove it. You can't show the intermediary steps in this evolution,” Lambert says in the press release. “And that was true, maybe thirty years ago. But now, with more teams working on the subject, we have a far more convincing scenario.”

Three Incredible Natural Areas Nominated for the World Heritage List

Smithsonian Magazine

In a month, the World Heritage Committee will vote to declare several new areas World Heritage Sites, a designation that gives important cultural, scientific and ecological areas international legal protection. Among the 35 nominations that will be voted on, there are seven natural areas up for consideration. Of those, the International Union for the Conservation of Nature, the body which assesses natural sites for World Heritage Status, currently recommends three for inclusion on the list, reports Andy Coghlan at New Scientist. The choices are expected to be accepted when the committee meets in July.

The first is Qinghai Hoh Xil, which Coghlan describes as the world’s "largest, highest and youngest" plateau. According to China’s nominating document, the area, in the northwestern part of the Qinghai-Tibet Plateau, is the range of the endemic Tibetan antelope, an endangered species with about 50,000 individuals left in the region. “The annual migration between its lambing ground and winter range is among the few significant migrations of terrestrial mammals on the planet and the sole example in China,” the document reads. 

Even more, it’s one of the few intact natural ecosystems in the world, and supports healthy communities of wolves, brown bear, Tibetan sand fox, and snow leopards which prey on species like wild yak, Tibetan gazelle, Tibetan pika and other endemic species. The ecosystem makes a full sweep from alpine wetlands through grasslands and steppes to alpine meadows and snowy mountains and glaciers.

Parque Nacional Los Alerces (Wikimedia Commons)

Another spot nominated for the list is Parque Nacional Los Alerces in Argentina, which protects the region’s Lahuán trees (Fitzroya cupressoides), the second-oldest trees on Earth with some clocking in at 3,600 years old.

Though it’s been a park since 1936, it faces threats. In 2016, wildfires destroyed 4,000 acres of the park. Coghlan reports that invasive salmon and interference with the headwaters of rivers running through the region also threaten the area.

According to its nominating document, the park protects one of the last intact swathes of the Valdivian Temperate Woods, the only temperate forest ecosystem in Central and South America. It’s home to the endangered Andean deer, the pudu, the smallest deer in the continent, as well as the austral spotted cat.

W National Park (Wikimedia Commons)

The third site up for consideration is an extension of Niger’s W National Park World Heritage Area into neighboring Benin and Burkina Faso. According to the World Heritage Council the area protects the transition zone from West African Savannah into forest and is in the heart of the most ecologically intact natural area in West Africa. Currently, the area is a complex of nine protected areas that is one of the last refuges of the West African elephant, African manatee, cheetah, lion, leopard and Topi antelope. It’s also home to many endemic fish in the Volta River basin.

Coghlan reports that the extension would expand the World Heritage Area, established in 1996, by sevenfold, to 3,700,000 acres.

"Lost Continent" Rises Again With New Expedition

Smithsonian Magazine

Tens of millions of years after it disappeared under the waters of the Pacific Ocean, scientists have completed the first explorations of what some scientists are calling a hidden continent, Naaman Zhou reports at the Guardian.

During a two-month ocean voyage this summer, a team of more than 30 scientists from 12 countries explored the submerged landmass of Zealandia on an advanced research vessel and collected samples from the seabed. Scientists were able to drill into the ocean floor at depths of more than 4,000 feet, collecting more than 8,000 feet of sediment cores that provides a window into 70 million years of geologic history, reports Georgie Burgess for ABC News.

More than 8,000 fossils from hundreds of species were also collected in the drilling, giving scientists a glimpse at terrestrial life that lived tens of millions of years ago in the area. "The discovery of microscopic shells of organisms that lived in warm shallow seas, and of spores and pollen from land plants, reveal that the geography and climate of Zealandia were dramatically different in the past," expedition leader Gerald Dickens said in a statement. While more than 90 percent of Zealandia is now submerged under more than a kilometer (two-thirds of a mile) of water, when it was above the surface, it likely provided a path that many land animals and plants could have used to spread across the South Pacific, notes Naaman Zhou of the Guardian.

The Geological Society of America officially endorsed the long-standing theory that a nearly 2 million-square-mile section of Pacific Ocean floor around the country of New Zealand was actually continental crust that had submerged beneath the water in a paper published by its journal in February. As Sarah Sloat reports for Inverse, this sinking, believed have taken place after the continent broke off from Australia around 60 to 85 million years ago, made New Zealand, and other seemingly disparate islands in the area, the remains of what was once a large landmass. 

However, classifying Zealandia as a continent is still a source of debate among scientists. In an interview with Michael Greshko of National Geographic in February, Christopher Scotese, a Northwestern University geologist was skeptical. “My judgment is that though Zealandia is continental, it is not a continent,” Scotese said. “If it were emergent, we would readily identify it with Australia, much like we identify Greenland with North America and Madagascar with Africa.” 

Scientists now plan to study the sediment cores and fossils to help create models of how the region looked and changed over the course of tens of millions of years, reports Sloat, and plans are always in the works for a return expedition next year.

Painting - Pendulum Momentum (Galileo)

National Museum of American History
The Greek mathematician Aristotle, who lived from about 384 BC through 322 BC, believed that heavy bodies moved naturally downward, while lighter substances such as air naturally ascended. Other forms of terrestrial motion required a sustaining force, which was not expressed mathematically. The Italian Galileo Galilei (1564–1642) challenged Aristotle. He held that motion was persistent and would continue until acted upon by an opposing, outside force. In a book entitled Dialogues Concerning the Two Chief World Systems, Galileo presented his ideas in a dispute between three men: Salviati, Sagredo, and Simplicio. Salviati, a spokesman for Galileo, explained his revolutionary ideas, one of which is illustrated by a diagram that was the basis for this painting. This image can be found in Crockett Johnson's copy of The World of Mathematics, a book by James R. Newman. It is probable that this image served as inspiration for this painting, although Johnson did not annotate this diagram. In Galileo's Dialogues, Salviati argued that if a lead weight is suspended by a thread from point A (see figure) and is released from point C, it will swing to point D, which is located at the same height as the initial point C. Furthermore, Salviati stated that if a nail is placed at point E so that the thread will snag on it, then the weight will swing from point C to point B and then up to point G, which is also located at the same height as the initial point C. The same occurs if a nail is placed at point F below the line segment CD. The painting is executed in purple that progresses from light tints to darker shades right to left. This gives the figure a sense of motion akin to that of a pendulum. The background is washed in gray and black. The line created by the initial and final height of the weight divides the background. Pendulum Momentum, a work in oil on masonite, is painting #13 in the Crockett Johnson series. It was executed in 1966 and is signed: CJ66. There is a wooden frame painted black.

'Staggering' Damage to Florida’s Everglades Remains in the Wake of Hurricane Irma

Smithsonian Magazine

In September of last year, as Hurricane Irma tore through the southern United States, fierce winds battered the Florida’s Everglades National Park. As Megan Gannon reports for Live Science, NASA scientists recently conducted an aerial survey of the Everglades to assess the impact of the storm—and found massive damage to the region's mangrove forests.

The research team was able to get a particularly good sense of forest casualties because in April of last year, several months before the storm hit, NASA surveyed the area using an airborne instrument called G-LiHT, which stands for Goddard’s Lidar, Hyperspectral and Thermal Imager. This device maps terrestrial ecosystems using thermal measurements, imaging spectroscopy and a remote sensing technique known as LiDAR. By sending out up to 500,000 laser pulses per second, LiDAR can create detailed 3-D maps of dense forested areas from far above the ground.

As NASA explains on its website, the goal of the 2017 project was to find out how freshwater ecosystems—like the marshes of the Everglades—are transitioning to saltwater ecosystems due to rising sea levels and coastal erosion. By comparing images from this dataset to information gleaned from the most recent aerial survey, researchers were able to assess how the Everglades changed after Irma.

The team returned to the area in December of this year, flying the same path across 500 square miles of wetlands and supplementing that information with 3D scans taken from the ground by local agencies. Researchers discovered that 60 percent of the area’s mangrove forests were severely damaged. Heavy winds had sliced off the limbs of trees and torn them out of the ground, creating gaps across 40 percent of the forest canopy in the surveyed area. The average height of the canopy dropped between three to five feet due to fallen trees and branches.

“It’s staggering how much was lost,” Lola Fatoyinbo, a remote sensing scientist at NASA’s Goddard Space Flight Center, said in the agency’s statement. “The question is, which areas will regrow and which areas won’t.”

The team plans to compare datasets from before and after the storm to see if areas that were under stress prior to Irma recover as quickly as ones that were not. As Maddie Stone explains in Earther, it is important to track the health of this ecosystem because the Everglades act as a buffer that protects residents of south Florida from storms and rising sea levels. “If the Glades are being weakened and lost by natural disasters, development and climate change,” Stone writes, “that’s bad news for the nearly seven million people living nearby.”

NASA researchers are now heading to Puerto Rico to conduct G-LiHT flights over areas that were hit hard by both Irma and Hurricane Maria last year.

“It’s a good way to document which areas were more susceptible to events like Hurricane Maria,” Bruce Cook, G-LiHT lead scientist at NASA Goddard. “And also it’s a way to start tracking recovery as well. A lot of people are interested in the recovery, and what we might be talking about in terms of reestablishing the forests in the future, and whether it will require human intervention.”

Crater morphometry and modification in the Sinus Sabaeus and Margaritifer Sinus regions of Mars

Smithsonian Libraries
Degraded craters in the southern highlands are indicative of an early martian climate much different than the present. Using a photoclinometric model, analyses of degraded crater morphometry have revealed the stages of crater modification and, for the first time, allow a quantitative assessment of the amount of material eroded in the highlands. Central peaks of fresh craters are removed early by degradational processes. The sharp rims of fresh craters also become rounded while the interior slopes become shallower. Continued degradation causes the crater rim to lower, and infilling produces a broad, flat crater floor. Contrary to earlier observations, the degree of rim modification does not appear to be dependent on the presence of ancient valley networks. During degradation, the diameter of the impact craters also increases due to backwasting. A simple algebraic model balancing the measured amount of infilling with that eroded from the interior slopes suggests that the crater diameters were enlarged by 7 to 10% initially, agreeing with prior observations. These models suggest that larger diameter (i.e., 50 km) craters were enlarged a greater amount than smaller diameter craters, which is opposite to what should be observed. To explain this discrepancy, a ?10 m thick deposit, presumably aeolian in origin, must have been emplaced within the crater interiors following cessation of the degradational process. By the terminal stage of degradation, crater diameters appear to have been enlarged by 30%. In addition, a deposit ?60 m average thickness must have been emplaced within these rimless craters to explain the discrepancy in crater enlargement. Because this deposit is contained only within the highly eroded, rimless craters, this material most likely originated from erosion of the surrounding terrain. The measured crater morphometry has allowed us to develop equations describing the amount of material eroded at any given stage of degradation. Applying these equations to craters within the Margaritifer Sinus and Sinus Sabaeus region indicates that an equivalent of ?200 m of highland material was eroded and redistributed within the study area. Depending upon model chronology, degradation operated for either 400 or 600 million years, suggesting that erosion rates were on the order of ?0.0003 to 0.0005 mm/yr. These erosion rates are equivalent to those determined for terrestrial periglacial environments. Two-dimensional simulations of some possible degradational processes suggest that fluvial erosion and deposition combined with diffusional creep come closest to producing equivalent degrees of modification through the range of crater diameters investigated in this study (20 to 50 km). However, these processes are inefficient at producing the amount of crater enlargement observed, suggesting that crater interior slopes may have also been undermined by sapping. These results imply that geologic processes related to precipitation dominated the early martian environment. Our working hypothesis is that this precipitation was due to the presence of a primordial atmosphere which condensed and collapsed (i.e., precipitated) into the martian regolith; a process which ceased during the late Hesperian/early Amazonian (3.5 to 1.8 Ga).

The ‘FlipperBot’ Is Almost as Cute as the Baby Sea Turtles It Mimics

Smithsonian Magazine

Baby sea turtles are an impressive example of nature’s engineering prowess. (Also, they are adorable.) The beaches on which they are born are plagued with predators looking to snatch up a quick turtle snack, and when the tiny turtles scramble out of their underground nests, their ability to hustle across the sand to the relative safety of the ocean determines if they live or die.

But anyone who has ever tried jogging through sand knows that moving on the shifting ground can be challenging. To make their way, sea turtles evolved a flexible flipper wrist that allows them to skim along without displacing too much sand. Not all of the turtles are expert crawlers, however. Some get stuck in ruts or tracks made by turtles before them.

Inspired by this ability and curious about why some turtles perform better than others, researchers from Georgia Tech and Northwestern University have built the FlipperBot, a bio-inspired robot that can navigate through granular surfaces like sand. ScienceNOW details the robot:

Based on footage of hatchlings collected on the Georgia coast, FBot reveals how the creatures exert a force that will propel them forward, without simply causing their limbs to sink into the sand. The flexible “wrist” of a turtle helps reduce such slipping, and prevents the creature from winding up with a snootful of sand.

Here, you can see the robot in action:

The researchers hope the robot may lend hints about beach restoration and conservation efforts. Discover details this idea from physicist Paul Umbanhowar:

Umbanhowar said understanding beach surfaces and how turtles move is important because many beaches in the United States are often subject to beach nourishment programs, where sand is dredged and dumped to prevent erosion.

“If you are restoring a beach, it might be the wrong kind of sand or deposited in a way that is unnatural,” Umbanhoward said. “In order for this turtle to advance, it has to generate these kind of thrust forces and it may be unable to get their flippers into it. We could say something about that given our models.”

Plus, the robot help explain how our distant ancestors managed to crawl out of the ocean and onto the land. The researchers hope to expand upon the FlipperBot to build a new robot that resembles our distant ancestor, the fish-amphibian hybrid Ichthyostega, ScienceNow reports.

“To understand the mechanics of how the first terrestrial animals moved, you have to understand how their flipper-like limbs interacted with complex, yielding substrates like mud flats,” the researchers said in a statement. “We don’t have solid results on the evolutionary questions yet, but this certainly points to a way that we could address these issues.”

More from Smithsonian.com:

Captive Sea Turtles Extract Their Revenge By Making Tourists Sick
Robots Inspired by Biology 

microscope

National Museum of American History
This is a compound monocular with coarse and fine focus, double nosepiece, square stage, inclination joint with handle, sub-stage diaphragm, sub-stage mirror, and horseshoe base. The inscription reads “E. Leitz Wetzlar / No 24997.” The serial number indicates a date of around 1892. The back of the base is marked “48?” This was used at the Department of Terrestrial Magnetism of the Carnegie Institution of Washington. Ref: Ernst Leitz, Petrological and Metallographic Microscopes (Wetzlar, 1910), pp. 14-17.

Sir Sandford Fleming's Pocketwatch

National Museum of American History
This watch belonged to Sir Sandford Fleming, chief engineer of the Canadian Pacific Railway. About 1880, Fleming devised a plan for worldwide time zones and had a complicated watch made to reflect both zoned time and local time.

The maker of Fleming's watch is the London firm of Nicole, Nielsen & Co. Successor to a business founded by Swiss immigrants Adolphe Nicole and Jules Capt in the late 1830s, the firm made high-quality timepieces. Fleming ordered the watch through retailer E. White, also of London.

Fleming's first notions about time reform emerged on a trip to Ireland in 1876, when he missed a train because he misread a timetable. His initial plan concentrated on replacing the two twelve-hour designations of the day, A.M. and P.M., with a twenty-four hour system. Almost immediately, though, he expanded his ideas about time reform to propose a system he called variously "Terrestrial Time," "Cosmopolitan Time," and "Cosmic Time"-a division of the globe into twenty-four zones, each one hour apart and identified by letters of the alphabet.

As the 1880s began there was no binding international agreement about how to keep time for the world. Traditionally, each country used its own capital city or main observatory for measuring time and designating lines of longitude on national maps. After publication of the British Nautical Almanac began in 1767, many nations came to use Greenwich time for navigation and some scientific observations. Local mean time served for all other activities.

Added emphasis on Greenwich had come from North America when the railroads there voluntarily adopted a standard zoned time in 1883. In that system, the zones were based on meridians counted west from Greenwich, England, at zero degree of longitude.

Fleming was not the first or only proponent of world standard time. Quirico Filopanti, an Italian mathematics and engineering professor, for example, published a scheme based on twenty-four zones counted from Rome as prime meridian in 1858.

Organized international support emerged slowly for fixing a common prime meridian. Not until October 1884 did diplomats and technical specialists gather to act on scientific proposals. The International Meridian Conference, held in Washington, DC, recommended that the nations of the world establish a prime meridian at Greenwich, count longitude east and west from the prime meridian up to 180 degrees in each direction, and adopt a universal day beginning at Greenwich at midnight. Although the International Meridian Conference had no authority to enforce its suggestions, the meeting resulted in the gradual worldwide adoption of a time-zone based system with Greenwich as zero degrees.

The military and some civilian science, aviation and navigation efforts still use alphabet identifiers for time zones. The time of day in Zone Z is known as "Zulu Time." The zone is governed by the zero degree of longitude that runs through Greenwich.

Bardin 18-inch Celestial Globe

National Museum of American History
This globe is supported on a wooden tri-leg pedestal, surrounded by a wooden horizon circle, and is equipped with a brass meridian and a small brass circle around the north pole. It (and its terrestrial mate) belonged to the eminent chemist, Joseph Priestley. The cartouche in the southern hemisphere has a text that reads: “To the Rev. / NEVIL MASKELYNE, D.D. F.R.S. / Astronomer Royal / The New British Celestial Globe / containing the Positions of nearly 6000 Stars, Clusters, nebulae, Planetary / Nebulae &c. Correctly computed & laid down to the year 1800; from the latest observati / ons and discoveries by Dr Maskelyne, Dr Herschel, The Revd Mr Wollaston &c. &c. / Is respectfully Dedicated / by his most obedient hbl Servants / W. & T. M. Bardin” William Bardin (fl. 1730-1798) was a London artisan who began making globes around 1780. Around 1790, now in partnership with his son, Thomas Marriott Bardin (1768-1819), he began trading as W. & T. M. Bardin. The 18-inch globes were their most ambitious. They were introduced in 1798, and remained in production, by successor firms, for a half century. Ref: John Millburn and Tör Rossaak, “The Bardin Family, Globe Makers in London” Der Globusfreund (1992). Elly Dekker, Globes at Greenwich (Oxford, 1999), pp. 260-270.

Black Mountain Lion and Black Fox

Smithsonian American Art Museum
The paintings of Awa Tsireh (1898-1955), who was also known by his Spanish name, Alfonso Roybal, represent an encounter between the art traditions of native Pueblo peoples in the southwestern United States and the American modernist art style begun in New York in the early twentieth century. The son of distinguished potters, Awa Tsireh translated geometic pottery designs into stylized watercolors that feature the ceremonial dancers and practices of Pueblo communities. But Awa Tsireh's work is more than an amalgam of traditional and modernist design. At a time when the U.S. Office of Indian Affairs attempted to restrict Pueblo cultural and religious practices, the watercolors of Awa Tsireh and other Pueblo artists helped to affirm the importance of ceremonial dance and tirual to cultural survival.

Awa Tsireh's paintings quickly found an audience among the artists, writers, and archaeologists who descended on Santa Fe in great numbers in the late 1910s and 1920s. Painter John Sloan and poet Alice Corbin Henderson took a particular interest and arranged for his watercolors to be exhibited in New York, Chicago, and elsewhere. Henderson shared with the young Pueblo painter books on European and American modernism and Japanese woodblock prints, as well as South Asian miniatures and ancient Egyptian art that provided soure material for his stylized paintings. In this way, he redefined contemporary Pueblo art and created a new, pan-Pueblo style.

The paintings in this exhibition were donated to the Smithsonian American Art Museum in 1979 by the Hendersons' daughter, Alice H. Rossin.
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