The research, led by UCLA planetary scientists and published in two papers in Geophysical Research Letters, could also indicate that alternating layers of volcanic and sedimentary rocks lie beneath the surface.

The 4.7 magnitude earthquake, or marsquake, happened in May 2022 and lasted more than four hours, releasing five times more energy than any previously recorded quake. Though moderate by Earth standards, the temblor was nonetheless powerful enough to send seismic surface waves completely around the planet’s circumference, the first time this phenomenon has been observed on Mars.

The readings were taken from InSight, which landed on Mars in 2018. InSight is the first outer space seismometer to study in-depth the “inner space” of Mars: its crust, mantle and core.

“The seismometer aboard the InSight lander has recorded thousands of marsquakes but never one this large, and it took over three years after landing to record it,” said corresponding author Caroline Beghein, a professor of Earth, planetary and space sciences. “This quake generated different kinds of waves, including two types of waves trapped near the surface. Only one of those two has been observed on Mars before, after two impact events, never during a marsquake.”

Mapping the seismic activity, the location and frequency of impacts on Mars and the interior structure is important for future missions to the red planet as it will inform scientists and engineers where and how to build structures to ensure the safety of future human explorers.

As on Earth, studying how seismic waves travel through rocks can give scientists clues about the temperature and composition of the planet below the surface that help inform the search for underground water or magma. It also helps scientists understand the past forces that shaped the planet.

Beghein’s group combined measurements from two types of surface waves, called Love and Rayleigh waves, to infer the speed of underground shear-waves, which travel horizontally and move rocks perpendicular to the direction of wave propagation. This is the first time Love waves have been observed in conjunction with Rayleigh waves on Mars.

The measurements showed that the shear-waves move faster in the crust when rocks between 10 and 25 kilometers underground oscillate in a direction almost parallel to the planet surface than if the rocks vibrate in the vertical direction.

“This wave speed information is related to deformations inside the crust,” Beghein said. “Alternating volcanic rocks and sedimentary layers, which were deposited long ago, or a very large impact, such as a meteoroid, most likely account for the seismic wave measurements we observed.”

These data also enabled Jiaqi Li, a UCLA postdoctoral researcher in Beghein’s group, to learn that shear-waves move faster in the Martian southern highland areas than in the northern lowlands. The northern hemisphere of Mars has a lower elevation and is covered with more craters than the southern hemisphere. A large impact in the lowlands has been the prevalent theory to explain the origin of this difference.

The new data point toward the presence of thick accumulations of sedimentary rocks and relatively higher porosity in the lowlands. Larger amounts of gas, such as trapped air in these sedimentary rocks, slow the waves down.

Story Source:

Materials provided by University of California – Los Angeles. Original written by Holly Ober. Note: Content may be edited for style and length.

The research is published in the journal npj Science of Learning.

“The context in which we learn things can help us remember them better,” said Jesse Rissman, the paper’s corresponding author and a UCLA associate professor of psychology. “We wanted to know if learning foreign languages in virtual reality environments could improve recall, especially when there was the potential for two sets of words to interfere with each other.”

Researchers asked 48 English-speaking participants to try to learn 80 words in two phonetically similar African languages, Swahili and Chinyanja, as they navigated virtual reality settings.

Wearing VR headsets, participants explored one of two environments — a fantasy fairyland or a science fiction landscape — where they could click to learn the Swahili or Chinyanja names for the objects they encountered. Some participants learned both languages in the same VR environment; others learned one language in each environment.

Participants navigated through the virtual worlds four times over the course of two days, saying the translations aloud each time. One week later, the researchers followed up with a pop quiz to see how well the participants remembered what they had learned.

The results were striking: Subjects who had learned each language in its own unique context mixed up fewer words and were able to recall 92% of the words they had learned. In contrast, participants who had learned both sets of words in the same VR context were more likely to confuse terms between the two languages and retained only 76% of the words.

The study is particularly timely because so many K-12 schools, colleges and universities moved to develop online learning platforms during the COVID-19 pandemic.

“Apps like Zoom provide a rather bland context for learning,” Rissman said. “As VR technology becomes more ubiquitous and affordable, remote learners could be instantly teleported into unique and richly featured contexts for each class.”

The experiment was designed by Rissman and Joey Ka-Yee Essoe, the study’s first author who was a UCLA doctoral student at the time.

Rissman said a key predictor of the subjects’ ability to retain what they had learned was how immersed in the VR world they felt. The less a participant felt like a subject in a psychology experiment — and the more “at one” they felt with their avatar — the more the virtual contexts were able to positively affect their learning.

“The more a person’s brain was able to reconstruct the unique activity pattern associated with the learning context, the better able they were to recall the foreign words they had learned there,” Rissman said.

Psychologists have long understood that people tend to recall things more readily if they can remember something about the surrounding context in which they learned it — the so-called “context crutch” phenomenon. But when information is tied to contextual cues, people can have trouble recalling it later in the absence of those cues.

For example, students might learn Spanish in the same kind of classroom where they learn other subjects. When that happens, their Spanish vocabulary can be tied to the same contextual cues that are tied to other material they’ve been taught, like the Pythagorean theorem or a Shakespeare play. Not only does that similar context make it easier to mix up or forget what they have learned, but it also can make it harder to remember any of the information outside of a classroom setting.

“A key takeaway is that if you learn the same thing in same environment, you’ll learn it really fast,” said Essoe, who is now a postdoctoral scholar at Johns Hopkins University. “But even though you learn fast, you might have trouble with recall. What we were able to harness in this research takes advantage of both learning fast and improving recall in new environment.”

To understand the brain mechanisms that support context-dependent learning, the researchers recruited a separate group of participants and scanned their brains with functional magnetic resonance imaging, or fMRI. As the subjects attempted to recall foreign words while in the scanner, their brain activity indicated that they were thinking about the context in which they had learned each word.

That finding suggests that virtual reality can enhance learning if it is convincingly produced and if different languages or scholastic subjects are taught in highly distinctive environments.

Rissman said although the study only assessed how people learned a foreign language, the results indicate that VR could be useful for teaching other subjects as well. Similar approaches could also be used for mental and behavioral health therapies and to help patients adhere to doctors’ instructions after medical visits: Patients might be able to remember such guidance better if they’re in their own homes while chatting online with their doctors, for example.

Said Essoe: “Variable contexts can ground information in more environmental cues.”

“There are two challenges every sea creature has to face: getting pure water in, so you can get oxygen to your gills, and getting rid of your waste. Because nobody wants to live in their poop. But here are these clams living with theirs, and actually thriving,” says Janet Voight, Associate Curator of invertebrate zoology at the Field Museum and the study’s lead author.

Scientists can put wood on the seafloor, return months or even years later, and recover it with “an amazing array of animals,” says Voight; other times wood that has been submerged for the same amount of time comes up so gnawed and bored-through that you can crumble it in your hand. This difference was a mystery, and Voight wanted to know why.

She took stock of the wood-boring clam species present in reports of sunken wood from all over the world, and she noticed a pattern. “There are six main branches in the wood-boring clam family tree, and every woodfall that was bored so heavily it was crushable by hand turned out to have been bored by a species from the same single branch of that family tree,” says Voight. She says she was surprised by this finding — “that’s not supposed to happen, you just assume that all wood-boring clam species, which tend to look pretty similar, bore into wood the same way. And yet, here’s one group that’s doing something totally different.”

Scientists had suggested that the extra-chewed-up wood was due to lots of larvae happening to be present nearby, or warmer water temperatures, but it turns out, the very nature of the clams may be responsible. Voight noted all of these extra-efficient, related species have a common trait where the sun don’t shine. As the clams dig and move into their boreholes in the wood, they fill the space around them inside the holes with their own feces.

“They don’t do it on purpose, their anatomy makes them do it,” says Voight. “When these clams bore into wood, their little shell does the boring.” Meanwhile, the clams’ siphons, tubular appendages for taking in water to get oxygen and expelling waste, stick out behind them. “In most wood-boring clams, these two “in and out” siphons are equal in length and stick out into the water column,” says Voight. “But in these related hyper-nasty borers, the siphon for expelling de-oxygenated water and feces is short; it stays inside the borehole in the wood. As a result, says Voight, “they poop in their borehole. They just have to, unless they really, really push.” The waste stays right there with the clam, forming a chimney that wraps around the siphon.

That animals would evolve an anatomy that keeps them in such close contact with their own waste, is surprising, says Voight: “It sure isn’t very hygienic, and yet they show no evidence of immune problems. They’re healthy, they’re clearly going to town on the wood. So why did they evolve this way?”

She and her colleagues hypothesized that these fecal chimneys might cue larval settlement: that their free-floating larvae might be able to detect the poop and make their way to it to make a home alongside members of their own species.

But that still leaves the problem: even if a poop chimney serves as a beacon for other members of their species to join them on their wood, how can these individuals survive as more and more larvae settle and the environment becomes filthier and oxygen becomes less available?

“This group of species of clam has been shown in previous studies to be unusually tolerant of low oxygen,” says Voight. They also have additional adaptations, like a mucosal lining of their fecal chimneys, and a substance like hemoglobin in their blood that picks up more oxygen; both may reduce the risk of sulfide poisoning from the waste. Taken together, these adaptations allow these speciesto survive in conditions that would make non-related wood-boring clams sick. The end result is more wood for the chimney-producing species to eat, live in, and for their offspring to settle on, unbothered by competitors.

Beyond just solving the mystery of the gross chewed-up wood with an even grosser solution, Voight says that the study illustrates the importance of looking at ecology with an understanding of how different species are related to each other.

“When you’re confronted with something that seems enigmatic, sometimes you need to step back and look at the big picture, put a lot of different studies together, to see how what had appeared to be enigmatic is a product of evolution,” says Voight. “Having a good family tree can help reveal patterns, and the more we know about the evolutionary histories of these different groups, the more we’ll be able to find out about how they fit together.”