craters Archives - ATLANTIS RISING THE RESEARCH REPORT

South Pole Hit Caused Big Differences Between Near and Far Side

The oldest unequivocal evidence of upright walking in the human lineage are footprints discovered at Laetoli, Tanzania, in 1978, by paleontologist Mary Leakey and her team, dated to 3.7 million years ago. Another set of mysterious footprints was partially excavated at a nearby location, known as site A, in 1976, but dismissed as possibly having been made by a bear. A recent re-excavation of the site A footprints at Laetoli and comparative analysis reveal that the footprints were made by an early human— a bipedal hominin, according to a new study reported in Nature.

“Given the increasing evidence for locomotor and species diversity in the hominin fossil record over the past 30 years, these unusual prints deserved another look,” says lead author Ellison McNutt, Guarini ’19, who started the work as a graduate student in the Ecology, Evolution, Environment, and Society program, and is now an assistant professor of instruction at the Heritage College of Osteopathic Medicine at Ohio University. At Dartmouth, she focused on the biomechanics of walking in early humans and utilized comparative anatomy, including that of bears.

McNutt was fascinated by the bipedal (upright walking) footprints at site A. Laetoli is famous for its impressive trackway of hominin footprints at sites G and S, which are generally accepted as Australopithecus afarensis—the species of the famous partial skeleton “Lucy.” But because the footprints at site A were so different, some researchers thought they were made by a young bear walking upright on its hind legs.

To determine the maker of the site A footprints, in June 2019, an international research team led by co-author Charles Musiba, an associate professor of anthropology at University of Colorado Denver and a Montgomery Fellow, went to Laetoli, where they re-excavated and fully cleaned the five consecutive footprints. They identified evidence that the fossil footprints were made by a hominin—including a large impression for the heel and the big toe. The footprints were measured, photographed, and 3D-scanned by Anjali Prabhat ’20; Catherine Miller, Guarini ’23; and Luke Fannin, Guarini ’24, who are co-authors of the paper.

The researchers compared the site A tracks to the footprints of black bears, chimpanzees, and humans.
They teamed up with co-authors Ben and Phoebe Kilham, who run the Kilham Bear Center, a rescue and rehabilitation center for black bears in Lyme, N.H. They identified four semi-wild juvenile black bears at the center with feet similar in size to that of the site A footprints. Each bear was lured with maple syrup or applesauce to stand up and walk on its two hind legs across a trackway filled with mud to capture its footprints.

AR #126,

“Morocco Homo Sapiens–a Small Step Forward?,”

Michael Cremo

South Pole Hit Caused Big Differences Between Near and Far Side

The face that the Moon shows to Earth looks far different from the one it hides on its far side. The nearside is dominated by the lunar mare — the vast, dark-colored remnants of ancient lava flows. The crater-pocked far side, on the other hand, is virtually devoid of large-scale mare features. Why the two sides are so different is one of the Moon’s most enduring mysteries.
Now, researchers have a new explanation for the two-faced Moon — one that relates to a giant impact billions of years ago near the Moon’s south pole.
A new study published in the journal Science Advances shows that the impact that formed the Moon’s giant South Pole–Aitken (SPA) basin would have created a massive plume of heat that propagated through the lunar interior. That plume would have carried certain materials — a suite of rare-Earth and heat-producing elements — to the Moon’s nearside. That concentration of elements would have contributed to the volcanism that created the nearside volcanic plains.
“We know that big impacts like the one that formed SPA would create a lot of heat,” said Matt Jones, a Ph.D. candidate at Brown University and the study’s lead author. “The question is how that heat affects the Moon’s interior dynamics. What we show is that under any plausible conditions at the time that SPA formed, it ends up concentrating these heat-producing elements on the nearside. We expect that this contributed to the mantle melting that produced the lava flows we see on the surface.”
The study was a collaboration between Jones and his advisor Alexander Evans, an assistant professor at Brown, along with researchers from Purdue University, the Lunar and Planetary Science Laboratory in Arizona, Stanford University and NASA’s Jet Propulsion Laboratory.
The Moon’s nearside (left) is dominated by vast volcanic deposits, while the far side (right) has far fewer). Why the two sides are so different is an enduring lunar mystery.
The differences between the near and far sides of the Moon were first revealed in the 1960s by the Soviet Luna missions and the U.S. Apollo program. While the differences in volcanic deposits are plain to see, future missions would reveal differences in the geochemical composition as well.
Some scientists have suspected a connection between the PKT and the nearside lava flows, but the question of why that suite of elements was concentrated on the nearside remained. For the study, the researchers conducted computer simulations of how heat generated by a giant impact would alter patterns of convection in the Moon’s interior, and how that might redistribute KREEP material in the lunar mantle. KREEP is thought to represent the last part of the mantle to solidify after the Moon’s formation. As such, it likely formed the outermost layer of mantle, just beneath the lunar crust. Models of the lunar interior suggest that it should have been more or less evenly distributed beneath the surface. But this new model shows that the uniform distribution would be disrupted by the heat plume from the SPA impact.