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China's Mars rover finds hints of catastrophic floods – Nature.com

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A radar on Zhurong can penetrate the surface to a depth of 100 metres.Credit: Xinhua/Shutterstock

China’s Zhurong rover has peered deep under the surface of Mars, finding evidence of two major floods that probably shaped the region the robot has been exploring since it landed in May 2021.

An analysis published in Nature today1 is the first result from Zhurong’s radar imager, which can probe up to 100 metres below the surface. “It is a very interesting paper, and I was particularly impressed by how deep they can see with this radar,” says Svein-Erik Hamran, a planetary scientist at the University of Oslo, who analysed the only previous data from ground-penetrating radar used on the planet, collected by NASA’s Perseverance rover.

The history of Zhurong’s landing site — on Utopia Planitia, vast plains in Mars’s northern hemisphere — has puzzled scientists. Some have theorized that water or ice was once a feature of the landscape. Observations from space have identified sedimentary deposits that suggest the region was once an ancient ocean or submerged by huge floods, and geological features, such as pitted cones, resemble structures formed by water or ice. In May, researchers analysed infrared images of the landing site taken by China’s Mars orbiter, Tianwen-1, and found hydrated minerals that could have formed when groundwater rose through the rock or ice melted.

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But the region could have also been covered in lava, concealing some of these hydrological processes in the subsurface. Eruptions from the volcano Elysium Mons to the east of the landing site, or other volcanic activity, could have covered the region in magma, as has been observed in other parts of the Utopia basin. By studying the radar data, researchers hope to understand what happened, and whether water or ice could still be lurking below the rocks. “We want to know what is going on beneath the surface,” says study co-author Liu Yang, a planetary scientist at the National Space Science Center in Beijing.

Below the surface

Zhurong is China’s first rover on the red planet, and it has been exploring the southern part of Utopia Planitia. The rover’s ground-penetrating radar transmits high-frequency radio waves that can penetrate the surface to a depth of between 3 and 10 metres, and low-frequency waves that can reach up to 100 metres underground but offer poorer resolution. The study authors analysed low-frequency data taken between 25 May and 6 September over more than 1,100 metres of terrain as Zhurong travelled south of its landing site. Radar signals reflect off materials under the surface, revealing the size of their grains and their ability to hold an electric charge. Stronger signals typically indicate larger objects.

The radar did not find any evidence of liquid water down to 80 metres, but it did detect two horizontal layers with interesting patterns. In a layer between 10 and 30 metres deep, the team reports, the reflection signals strengthened with increasing depth. The researchers say this is probably due to larger boulders resting at the base of the layer, and smaller rocks settling on top. An older, thicker layer between 30 and 80 metres down showed a similar pattern.

The older layer is probably the result of rapid flooding that carried sediments to the region more than three billion years ago, when there was a lot of water activity on Mars, says co-author Chen Ling, a seismologist at the Institute of Geology and Geophysics, Chinese Academy of Sciences, in Beijing.

The upper layer could have been created by another flood some 1.6 billion years ago, when there was lots of glacial activity. Chen says it is unlikely that the upper layer contains intact lava flows, because it has a smaller ability to hold an electric charge than would be expected for intact volcanic rocks. Furthermore, the researchers didn’t see any sudden changes in layering, which would be expected when lava flows meet sedimentary material.

Volcanic or sedimentary?

But, Chen says, it is possible that a thin coat of lava once covered the upper layer and it has gradually been broken down into smaller pieces. Radar data alone cannot definitively reveal whether material is sedimentary or volcanic, says Xu Yi, a planetary scientist at Macau University of Science and Technology.

Radar data are good at indicating the layering and geometry of subsurface material, but not so good at pinpointing its composition, including whether the material is ice or rock, says Hamran. Often, researchers rely on other clues, such as rocks peering out from the surface, to build a picture of past events, he says. The authors say they can’t rule out the possibility that the region contains buried saline ice.

More radar results are expected from the mission, including data taken during Zhurong’s continued traverse of Mars, results from the high-frequency radar measurements already made, and Tianwen-1’s orbital radar observations, which penetrate deep into the planet. They could help to clarify details of the terrain. “This is only the first step,” say Ling.

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One Great Shot: Bucktoothed Bumpheads on the Great Barrier Reef – Hakai Magazine

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When I set out to photograph bumphead parrotfish on a three-week dive trip to the northern reaches of Australia’s Great Barrier Reef in the winter of 2021, I had a specific goal in mind: I wanted to see a school of these strange animals swimming together.

There are so many weird and wonderful ocean-dwelling creatures, but this particular parrotfish species stands alone with its bizarre overbite, formidable size, prominent forehead, and tendency to travel in large groups. Bumpheads can grow to more than a meter long and about 46 kilograms—about the same weight as the average adult chimpanzee—making them the largest parrotfish and one of the world’s biggest reef fish. They also play an important role in the ecosystem: with their beaklike teeth, they munch algae off corals. In the process, they swallow other reef material and excrete it as sand.

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One morning, on a pre-sunrise dive, I descended toward a reef where other divers had spotted bumpheads, hoping for my chance. Luck was on my side—it wasn’t long before I found a cluster of about 40 individuals huddled near the coral. The fish appeared to be completely still above a small bommie (reef) and were packed so tightly that their bodies were touching one another. When I edged closer, the parrotfish squeezed together even more, monitoring my every move. Reef fish are notoriously skittish, but this school stayed put while I took a picture.

The underwater world is full of fascinating species. Photographing them in their habitat is both challenging and rewarding, and I love sharing these moments with others.

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Author bio

Josh Blank is an underwater photographer based on the east coast of Australia. With a strong focus on larger marine species, Blank aims to use his imagery to inspire others to learn more about our blue planet and to seek out similar wildlife experiences themselves. He believes impactful ocean imagery is a valuable tool that can invoke change and ultimately achieve a better, more sustainable future.



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Cite this Article:
Josh Blank “One Great Shot: Bucktoothed Bumpheads on the Great Barrier Reef,” Hakai Magazine, Dec 9, 2022, accessed December 9th, 2022, https://hakaimagazine.com/videos-visuals/one-great-shot-bucktoothed-bumpheads-on-the-great-barrier-reef/.

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New branch on tree of life includes ‘lions of the microbial world’

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There’s a new branch on the tree of life and it’s made up of predators that nibble their prey to death.

These microbial predators fall into two groups, one of which researchers have dubbed “nibblerids” because they, well, nibble chunks off their prey using tooth-like structures. The other group, nebulids, eat their prey whole. And both comprise a new ancient branch on the tree of life called “Provora,” according to a paper published today in Nature.

Microbial lions

Like lions, cheetahs, and more familiar predators, these microbes are numerically rare but important to the ecosystem, says senior author Dr. Patrick Keeling, professor in the UBC department of botany. “Imagine if you were an alien and sampled the Serengeti: you would get a lot of plants and maybe a gazelle, but no lions. But lions do matter, even if they are rare. These are lions of the microbial world.”

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Using water samples from marine habitats around the world, including the coral reefs of Curaçao, sediment from the Black and Red seas, and water from the northeast Pacific and Arctic oceans, the researchers discovered new microbes. “I noticed that in some water samples there were tiny organisms with two flagella, or tails, that convulsively spun in place or swam very quickly. Thus began my hunt for these microbes,” said first author Dr. Denis Tikhonenkov, senior researcher at the Institute for Biology of Inland Waters of the Russian Academy of Sciences.

Dr. Tikhonenkov, a long-time collaborator of the UBC co-authors, noticed that in samples where these microbes were present, almost all others disappeared after one to two days. They were being eaten. Dr. Tikhonenkov fed the voracious predators with pre-grown peaceful protozoa, cultivating the organisms in order to study their DNA.

“In the taxonomy of living organisms, we often use the gene ’18S rRNA’ to describe genetic difference. For example, humans differ from guinea pigs in this gene by only six nucleotides. We were surprised to find that these predatory microbes differ by 170 to 180 nucleotides in the 18S rRNA gene from every other living thing on Earth. It became clear that we had discovered something completely new and amazing,” Dr. Tikhonenkov said.

New branch of life

On the tree of life, the animal kingdom would be a twig growing from one of the boughs called “domains,” the highest category of life. But sitting under domains, and above kingdoms, are branches of creatures that biologists have taken to calling “supergroups.” About five to seven have been found, with the most recent in 2018 — until now.

Understanding more about these potentially undiscovered branches of life helps us understand the foundations of the living world and just how evolution works.

“Ignoring microbial ecosystems, like we often do, is like having a house that needs repair and just redecorating the kitchen, but ignoring the roof or the foundations,” said Dr. Keeling. “This is an ancient branch of the tree of life that is roughly as diverse as the animal and fungi kingdoms combined, and no one knew it was there.”

The researchers plan to sequence whole genomes of the organisms, as well as build 3D reconstructions of the cells, in order to learn about their molecular organization, structure and eating habits.

International culture

Culturing the microbial predators was no mean feat, since they require a mini-ecosystem with their food and their food’s food just to survive in the lab. A difficult process in itself, the cultures were initially grown in Canada and Russia, and both COVID and Russia’s war with Ukraine prevented Russian scientists from visiting the lab in Canada in recent years, slowing down the collaboration.

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How A Hellish Planet Made Of Diamonds Covered By A Lava Ocean Got Where It Is Today

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In recent decades it’s become clear that the universe is teeming with planets and astronomers have begun to catalog them by the hundreds. Most of the worlds we’ve discovered so far are remarkably inhospitable and the closer we look at some, the more hellacious they seem to appear.

Case in point is 55 Cancri e, also known as 55 Cnc or by its nickname, Janssen. This world orbits so close to its star, known as Copernicus or 55 Cnc, that a year on its surface passes in only 18 hours and temperatures can soar over 4,000 degrees Fahrenheit.

Enduring such extreme conditions for so long has led scientists to suggest that the scalding world could have an interior full of diamonds, covered by a surface ocean of molten lava.

Makes Mauna Loa seem almost minor league on the cosmic scale of volcanism.

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There’s a reason that we keep spotting so many relatively hot planets next to their stars. Call it an inherent bias of our existing tech: it’s just easier to see planets orbiting close in to their stars.

In fact, most exoplanets discovered and cataloged so far have a very good chance of being so-called “hot Jupiters” — giant planets orbiting close-in. Being massive and next to your local source of light makes you especially easy to spot.

So 55 Cancri e is actually an important exoplanet as one of the first small, rocky planets found orbiting extremely close to its star.

Now researchers have made use of a new tool called EXPRES (for EXtreme PREcision Spectrometer) at the Lowell Discovery Telescope in Arizona to make ultra-precise measurements that helped them determine the orbit of this hellish world in more detail.

They found that the planet orbits Copernicus right along the equator of the star and that it likely originally orbited further out and was slowly pulled into its current alignment by the gravitational pull of the star and other objects in the unusual star system.

The system is located only 40 light years from Earth and consists of main-sequence star Copernicus paired with a red dwarf star. The binary duo also count at least five exoplanets that all have very different orbits among their cosmic family.

The new research, led by Lily Zhao at Flatiron Institute’s Center for Computational Astrophysics and published in Nature Astronomy, posits that the interactions between these oddball family members shifted Janssen to its current, insufferable orbit.

Although it was pushed, pulled and prodded into its current position, Zhao says that even in its original orbit, the planet “was likely so hot that nothing we’re aware of would be able to survive on the surface.”

What a waste of so much diamond.

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