Tag Archives: #crater

Researchers Discover New Type of Ancient Crater Lake on Mars (Planetary Science)

An ancient crater lake in the southern highlands of Mars appears to have been fed by glacial runoff, bolstering the idea that the Red Planet had a cold and icy past.

Researchers from Brown University have discovered a previously unknown type of ancient crater lake on Mars that could reveal clues about the planet’s early climate.

In a study published in Planetary Science Journal, a research team led by Brown Ph.D. student Ben Boatwright describes an as-yet unnamed crater with some puzzling characteristics. The crater’s floor has unmistakable geologic evidence of ancient stream beds and ponds, yet there’s no evidence of inlet channels where water could have entered the crater from outside, and no evidence of groundwater activity where it could have bubbled up from below.

So where did the water come from?

The researchers mapped where water flowed and ponded within the crater floor. © Brown University

The researchers conclude that the system was likely fed by runoff from a long-lost Martian glacier. Water flowed into the crater atop the glacier, which meant it didn’t leave behind a valley as it would have had it flowed directly on the ground. The water eventually emptied into the low-lying crater floor, where it left its geological mark on the bare Martian soil.

The type of lake described in this study differs starkly from other Martian crater lakes, like those at Gale and Jezero craters where NASA rovers are currently exploring.

“This is a previously unrecognized type of hydrological system on Mars,” Boatwright said. “In lake systems characterized so far, we see evidence of drainage coming from outside the crater, breaching the crater wall and in some cases flowing out the other side. But that’s not what is happening here. Everything is happening inside the crater, and that’s very different than what’s been characterized before.”

Importantly, Boatwright says, the crater provides key clues about the early climate of Mars. There’s little doubt that the Martian climate was once warmer and wetter than the frozen desert the planet is today. What’s less clear, however, is whether Mars had an Earthlike climate with continually flowing water for millennia, or whether it was mostly cold and icy with fleeting periods of warmth and melting. Climate simulations for early Mars suggest temperatures rarely peaking above freezing, but geological evidence for cold and icy conditions has been sparse, Boatwright says. This new evidence of ancient glaciation could change that. 

“The cold and icy scenario has been largely theoretical — something that arises from climate models,” Boatwright said. “But the evidence for glaciation we see here helps to bridge the gap between theory and observation. I think that’s really the big takeaway here.”

Boatwright was able to map out the details of the crater’s lake system using high-resolution images taken by NASA’s Mars Reconnaissance Orbiter. The images revealed a telltale signature of ancient streambeds — features called inverted fluvial channels. When water flows across a rocky surface, it can leave behind course-grained sediment inside the valley it erodes. When these sediments interact with water, they can form minerals that are harder than the surrounding rock. As further erosion over millions of years whittles the surrounding rock away, the mineralized channels are left behind as raised ridges spidering across the landscape. These features, along with sediment deposits and shoreline features, clearly show where water flowed and ponded on the crater floor.

A topographic map shows the raised ridges (dark yellow) and low-lying areas where water ponded (white). © Brown University

But without any sign of an inlet channel where water entered the crater, “the question becomes ‘how did these get here?”’ Boatwright said. 

To figure it out, Boatwright worked with Jim Head, his advisor and a research professor at Brown. They ruled out groundwater activity, as the crater lacked telltale sapping channels that form in groundwater systems. These channels usually appear as short, stubby channels that lack tributaries — completely opposite from the dense, branching networks of inverted channels observed in the crater. A careful examination of the crater wall also revealed a distinct set of ridges that face upward toward the crater wall. The features are consistent with ridges formed where a glacier terminates and deposits mounds of rocky debris. Taken together, the evidence points to a glacier-fed system, the researchers concluded.

Subsequent research has shown that this crater isn’t the only one of its kind. At this month’s Lunar and Planetary Science Conference, Boatwright presented research revealing more than 40 additional craters that appear to have related features.

Head says that these new findings could be critical in understanding the climate of early Mars.

“We have these models telling us that early Mars would have been cold and icy, and now we have some really compelling geological evidence to go with it,” Head said. “Not only that, but this crater provides the criteria we need to start looking for even more evidence to test this hypothesis, which is really exciting.”

Featured image: Raised ridges spidering across the floor of a Martian crater were likely created by runoff from a long-lost glacier that once draped the planet’s southern highlands. Credit: NASA

Reference: Benjamin D. Boatwright and James W. Head, “A Noachian Proglacial Paleolake on Mars: Fluvial Activity and Lake Formation within a Closed-source Drainage Basin Crater and Implications for Early Mars Climate”, Planetary Science Journal, 2(2), 2021. https://iopscience.iop.org/article/10.3847/PSJ/abe773

Provided by Brown University

The World’s Oldest Crater From A Meteorite Isn’t An Impact Crater After All (Planetary Science)

Several years after scientists discovered what was considered the oldest crater a meteorite made on the planet, another team found it’s actually the result of normal geological processes. 

Several years after scientists discovered what was considered the oldest crater a meteorite made on the planet, another team found it’s actually the result of normal geological processes. 

During fieldwork at the Archean Maniitsoq structure in Greenland, an international team of scientists led by the University of Waterloo’s Chris Yakymchuk found the features of this region are inconsistent with an impact crater. In 2012, a different team identified it as the remnant of a three-billion-year-old meteorite crater.

“Zircon crystals in the rock are like little time capsules,” said Yakymchuk, a professor in Waterloo’s Department of Earth and Environmental Sciences. “They preserve ancient damage caused by shockwaves you get from a meteorite impact. We found no such damage in them.”

Additionally, there are multiple places where the rocks melted and recrystallized deep in the Earth. This process—called metamorphism—would occur almost instantaneously if produced from an impact. The Waterloo-led team found it happened 40 million years later than the earlier group proposed.

“We went there to explore the area for potential mineral exploration, and it was through close examination of the area and data collected since 2012 that we concluded the features are inconsistent with a meteorite impact,” Yakymchuk said. “While we were disappointed that we weren’t working in a structure that was the result of a meteorite hitting the planet three billion years ago, science is about advancing knowledge through discovery, and our understanding of the Earth’s ancient history continues to evolve. Our findings provide scientific data for resource companies and Greenlandic prospectors to find new mineral resources.”

The study, Stirred not shaken; critical evaluation of a proposed Archean meteorite impact in West Greenland, by Yakymchuk and an international team of scientists from Canada, Australia, Denmark, Greenland and the United Kingdom, appears in the journal Earth and Planetary Science Letters.

Reference: Chris Yakymchuk, Christopher L. Kirkland, Aaron J. Cavosie, Kristoffer Szilas, Julie Hollis, Nicholas J. Gardiner, Pedro Waterton, Agnete Steenfelt, Laure Martin, “Stirred not shaken; critical evaluation of a proposed Archean meteorite impact in West Greenland”, Earth and Planetary Science Letters, Volume 557, 2021, 116730, ISSN 0012-821X, https://doi.org/10.1016/j.epsl.2020.116730.

Provided by University of Waterloo

What Are The Effects of Temperature, Impact Velocity & Impactor Density On Crater Shape? (Planetary Science)

Iron meteorites are composed of iron-nickel alloys and classified structurally into hexahedrites (5–6.5 wt% Ni), octahedrites (6–12 wt% Ni), and ataxites (~10 to >20 wt% Ni). Iron meteorites are also classified chemically in terms of the concentrations of trace elements, for example Ge and Ga, into several groups. Comparisons of the chemical trends within groups suggest that there are two different types: magmatic and non-magmatic. Magmatic groups are thought to be derived from the metallic cores of differentiated bodies whereas non-magmatic groups may come from bodies that were not heated enough to form metallic cores. The cores formed in the parent bodies of magmatic iron meteorites less than ~1.0 Myr after the formation of calcium-, aluminum-rich inclusions (CAIs), whereas chondrule ages are about 2–4 Myr after CAIs.

In 2006, Bottke et al. suggested that the parent bodies of iron meteorites are considered to have formed early in the terrestrial planet region before migrating to the main asteroid belt by gravitational interactions with protoplanets. Asteroid 16 Psyche is the largest metal-rich asteroid in the main asteroid belt, measuring 232×189×279 km, and might be such a remnant. The equilibrium temperature of the iron meteorites’ parent bodies decreased from about 300 K to 160 K during migration from the terrestrial planet region to the main asteroid belt. Some iron meteorites undergo a transition from ductile to brittle behavior as the temperature decreases. Moreover, the most probable collision velocity in the main asteroid belt is 4.4 km/s, however, it could have been higher in the terrestrial planet region early in the solar system. Such a velocity difference may also cause a difference in crater shape on metallic bodies.

Now, Ogawa and colleagues conducted impact experiments on room- and low-temperature iron meteorite and iron alloy targets (carbon steel SS400 and iron-nickel alloy) with velocities of 0.8–7 km s¯1, using a two-stage hydrogen-gas gun installed at the Institute of Space and Astronautical Science (ISAS) and a vertical powder gun at Kobe University, to investigate the dependence of crater shape on temperature, velocity and impactor density.

Figure 1. Cross-sections of the craters formed by copper projectiles (a) at room temperature with a velocity of 2.38 km s¯1 (Sc1), at low temperature (b) with velocities of 2.14 km s¯1 (Sc6), and (c) 6.08 km s¯1 (Sc9). © Nakamura et al.

The projectiles were rock cylinders and metal spheres and cylinders. They also conducted Oblique impact experiments using stainless steel projectiles and SS400 steel targets which produced more prominent radial patterns downrange at room temperature than at low temperature. Crater diameters and depths were measured and compiled using non-dimensional parameter sets based on the π -group crater scaling relations. They also performed iSALE-2D simulations using the Johnson– Cook (JNCK) strength model assuming JNCK parameters for the Gibeon iron meteorite, SS400 and SUS304.

The laboratory and numerical results collectively show that the depth/diameter (d/D) values of metallic targets are more dependent on velocity (U) than are those of rocky targets. The ratio is smaller under low velocity and low-temperature conditions; however, the ratio is more sensitive to U than it is to the temperature of the target.”

— told Nakamura, author of the study

Both experimental and numerical results showed that the crater depth and diameter decreased with decreasing temperature, which strengthened the target, and with decreasing impact velocity. The decreasing tendency was more prominent for depth than for diameter, i.e., the depth/diameter (d/D) ratio was smaller for the low temperature and low velocity conditions. The depth/diameter ratios of craters formed by rock projectiles were shallower than those of craters formed by metallic projectiles. Their results imply that the d/D values of craters on metallic surfaces contain information about the past impact environment of metallic bodies.

Featured image: The definitions of crater diameter, crater depth and rim height used in this study. On the left is the numerical result and on the right is the experimental result for an SUS-Gibeon 5.1-km/s impact (Gs4). The black and gray parts of the numerical result represent the projectile and target materials, respectively © Nakamura et al.

Reference: Ryo Ogawa, Akiko M. Nakamura, Ayako Suzuki, Sunao Hasegawa, “Crater shape as a possible record of the impact environment of metallic bodies: Effects of temperature, impact velocity and impactor density”, ArXiv, pp. 1-63, 4 Mar 2021. https://arxiv.org/abs/2103.03128

Copyright of this article totally belongs to our author S. Aman. One is allowed to reuse it only by giving proper credit either to him or to us

Asteroid Dust Found in Crater Closes Case of Dinosaur Extinction (Geology / Paleontology)

Researchers believe they have closed the case of what killed the dinosaurs, definitively linking their extinction with an asteroid that slammed into Earth 66 million years ago by finding a key piece of evidence: asteroid dust inside the impact crater.

Death by asteroid rather than by a series of volcanic eruptions or some other global calamity has been the leading hypothesis since the 1980s, when scientists found asteroid dust in the geologic layer that marks the extinction of the dinosaurs. This discovery painted an apocalyptic picture of dust from the vaporized asteroid and rocks from impact circling the planet, blocking out the sun and bringing about mass death through a dark, sustained global winter – all before drifting back to Earth to form the layer enriched in asteroid material that’s visible today.

In the 1990s, the connection was strengthened with the discovery of a 125-mile-wide Chicxulub impact crater beneath the Gulf of Mexico that is the same age as the rock layer. The new study seals the deal, researchers said, by finding asteroid dust with a matching chemical fingerprint within that crater at the precise geological location that marks the time of the extinction.

The crater left by the asteroid that wiped out the dinosaurs is located in the Yucatán Peninsula. It is called Chicxulub after a nearby town. Part of the crater is offshore and part of it is on land. The crater is buried beneath many layers of rock and sediment. A 2016 mission led by the International Ocean Discovery Program extracted rock cores from the offshore portion of the crater. Credit: The University of Texas at Austin/Jackson School of Geosciences/ Google Map.

“The circle is now finally complete,” said Steven Goderis, a geochemistry professor at the Vrije Universiteit Brussel, who led the study published in Science Advances on Feb. 24.

The study is the latest to come from a 2016 International Ocean Discovery Program mission co-led by The University of Texas at Austin that collected nearly 3,000 feet of rock core from the crater buried under the seafloor. Research from this mission has helped fill in gaps about the impactthe aftermath and the recovery of life.

The telltale sign of asteroid dust is the element iridium – which is rare in the Earth’s crust, but present at elevated levels in certain types of asteroids. An iridium spike in the geologic layer found all over the world is how the asteroid hypothesis was born. In the new study, researchers found a similar spike in a section of rock pulled from the crater. In the crater, the sediment layer deposited in the days to years after the strike is so thick that scientists were able to precisely date the dust to a mere two decades after impact.

“We are now at the level of coincidence that geologically doesn’t happen without causation,” said co-author Sean Gulick, a research professor at the UT Jackson School of Geosciences who co-led the 2016 expedition with Joanna Morgan of Imperial College London. “It puts to bed any doubts that the iridium anomaly [in the geologic layer] is not related to the Chicxulub crater.”

Sean Gulick, a research professor at The University of Texas at Austin Jackson School of Geosciences (right), and Joanna Morgan, a professor at Imperial College London, examine rock cores retrieved from the crater during the 2016 research mission led by the International Ocean Discovery Program. Credit: The University of Texas at Austin/ Jackson School of Geosciences.

The dust is all that remains of the 7-mile-wide asteroid that slammed into the planet millions of years ago, triggering the extinction of 75% of life on Earth, including all nonavian dinosaurs.

Researchers estimate that the dust kicked up by the impact circulated in the atmosphere for no more than a couple of decades – which, Gulick points out, helps time how long extinction took.

“If you’re actually going to put a clock on extinction 66 million years ago, you could easily make an argument that it all happened within a couple of decades, which is basically how long it takes for everything to starve to death,” he said.

A section of rock core pulled from the crater left by the asteroid impact that wiped out the dinosaurs. Researchers found high concentrations of the element iridium –a marker for asteroid material –in the middle section of the core, which contains a mixture of ash from the impact and ocean sediment deposited over decades. The iridium is measured in parts per billion. Credit: International Ocean Discovery Program.

The highest concentrations of iridium were found within a 5-centimeter section of the rock core retrieved from the top of the crater’s peak ring – a high-elevation point in the crater that formed when rocks rebounded then collapsed from the force of impact.

The iridium analysis was carried out by labs in Austria, Belgium, Japan and the United States.

“We combined the results from four independent laboratories around the world to make sure we got this right,” said Goderis.

In addition to iridium, the crater section showed elevated levels of other elements associated with asteroid material. The concentration and composition of these “asteroid elements” resembled measurements taken from the geologic layer at 52 sites around the world.

The core section and geologic layer also have earthbound elements in common, including sulfurous compounds. A 2019 study found that sulfur-bearing rocks are missing from much of the rest of the core despite being present in large volumes in the surrounding limestone. This indicates that the impact blew the original sulfur into the atmosphere, where it may have made a bad situation worse by exacerbating global cooling and seeding acid rain.

Gulick and colleagues at the University of Texas Institute for Geophysics and Bureau of Economic Geology – both units of the UT Jackson School – plan to return to the crater this summer to begin surveying sites at its center, where they hope to plan a future drilling effort to recover more asteroid material.

Featured image: The asteroid impact led to the extinction of 75% of life, including all non-avian dinosaurs. Credit: Willgard Krause/Pixabay.

Reference: Steven Goderis, Honami Sato, Ludovic Ferrière, Birger Schmitz, David Burney, Pim Kaskes, Johan Vellekoop, Axel Wittmann, Toni Schulz, Stepan M. Chernonozhkin, Philippe Claeys, Sietze J. de Graaff, Thomas Déhais, Niels J. de Winter, Mikael Elfman, Jean-Guillaume Feignon, Akira Ishikawa, Christian Koeberl, Per Kristiansson, Clive R. Neal, Jeremy D. Owens, Martin Schmieder, Matthias Sinnesael, Frank Vanhaecke, Stijn J. M. Van Malderen, Timothy J. Bralower, Sean P. S. Gulick, David A. Kring, Christopher M. Lowery, Joanna V. Morgan, Jan Smit, Michael T. Whalen, IODP-ICDP Expedition 364 Scientists, “Globally distributed iridium layer preserved within the Chicxulub impact structure”, Science Advances 24 Feb 2021: Vol. 7, no. 9, eabe3647 DOI: 10.1126/sciadv.abe3647

Provided by University of Texas

3D Model Shows Off The Insides of a Giant Permafrost Crater (Geology)

Researchers from the Oil and Gas Research Institute of the Russian Academy of Sciences and their Skoltech colleagues have surveyed the newest known 30-meter deep gas blowout crater on the Yamal Peninsula, which formed in the summer of 2020. The paper was published in the journal Geosciences.

Giant craters in the Russian Arctic, thought to be the remnants of powerful gas blowouts, first attracted worldwide attention in 2014, when the 20 to 40-meter wide Yamal Crater was found quite close to the Bovanenkovo gas field. The prevailing hypothesis is that these craters are formed after gas is accumulated in cavities in the upper layers of permafrost, and increasing pressure ultimately unleashes an explosive force. Most of these craters are rather short-lived as they apparently quickly fill with water over several years and turn into small lakes. As of now, there are some 20 known and studied craters.

In 2020, researchers found and surveyed the latest crater, dubbed C17, about 25 meters in diameter. It was found by Andrey Umnikov, director of the non-profit partnership “Russian Center of Arctic Development,” during a helicopter flight on July 16 in the central part of the Yamal Peninsula, close to three other craters including the famous Yamal Crater. OGRI deputy director Vasily Bogoyavlensky led the August 2020 expedition, which was possible thanks to the generous support of the government of Yamalo-Nenets Autonomous Area and Mr Umnikov’s organization. Evgeny Chuvilin and Boris Bukhanov from the Skoltech Center for Hydrocarbon Recovery took part in the expedition.

“The new crater is impressive in its ideal state of preservation, primarily the cone-shaped top where ejecta was thrown from, the outer parts of the heaving mound that precipitated the crater, the walls of the crater itself which are incredibly well preserved, and, of course, the gas cavity in the icy bottom of the crater,” Chuvilin says.

“Firstly, we got there in time to find the object in its almost pristine state, with no water filling it. Secondly, the giant underground cavity in the ice is unique in itself. A part of the icy dome of this cavity was preserved; before the explosion, it had this circular dome, and its bottom was elliptical, elongated to the north, with its axis ratio of approximately 1 to 4.5. From what we know we can say that the C17 crater is linked to a deep fault and an anomalous terrestrial heat flow,” Bogoyavlensky notes.

A certified pilot, Igor Bogoyavlensky, piloted the drone used for crater surveillance. That was the first time a drone flew inside the crater for “underground aerial survey” 10 to 15 meters below ground, running the risk of losing the aircraft. The team used the data to build a 3D model based on the drone footage from inside the crater. This is the first time scientists were able to study a “fresh” crater that has not yet eroded or filled with water, with a well-preserved ice cavity where gas had been accumulating. 3D modeling was earlier used for the Yamal Crater, but at the time it was already filled with water.

“Over the years we’ve gained a lot of experience with surveillance drones, yet this “underground aerial survey” of the C17 crater was the most difficult task I had ever faced, having to lie down on the edge of a 10-story deep crater and dangle down my arms to control the drone. Three times we got close to losing it, but succeeded in getting the data for the 3D model,” Igor Bogoyavlensky, the drone pilot, says.

Vasily Bogoyavlensky says the 3D model allowed them to capture the extremely complex shape of the underground cavity. “We could not see everything from above, especially the grottos, possible caverns in the lower part of the crater. You can clearly see all that with the 3D model. Our results suggest unequivocally that the crater was formed endogenously, with ice melting, a heaving mound dynamically growing due to gas accumulation and the explosion,” he adds.

The Skoltech researchers were able to study the cryogeological conditions of the crater, the composition of permafrost in this area as well as ejecta from the crater, temperature conditions at the crater floor and some other parameters. “This information will shed light on the conditions and formation of these unusual objects in the Arctic,” Chuvilin points out. 

In 2021, OGRI and Skoltech researchers are planning a new expedition to this crater to monitor its state and conduct further research into how it was formed.

Featured image: C17 Crater © Evgeny Chuvilin

Reference: Bogoyavlensky, Vasily; Bogoyavlensky, Igor; Nikonov, Roman; Kargina, Tatiana; Chuvilin, Evgeny; Bukhanov, Boris; Umnikov, Andrey. 2021. “New Catastrophic Gas Blowout and Giant Crater on the Yamal Peninsula in 2020: Results of the Expedition and Data Processing” Geosciences 11, no. 2: 71. https://doi.org/10.3390/geosciences11020071

Provided by Skoltech

Identical Evolution of Isolated Organisms (Paleontology)

Researchers at FAU prove parallel evolution of conodonts.

Palaeontologists at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) and the University of Calgary in Canada have provided new proof of parallel evolution: conodonts, early vertebrates from the Permian period, adapted to new habitats in almost identical ways despite living in different geographical regions. The researchers were able to prove that this was the case using fossil teeth found in different geographical locations. Their findings have now been published in the journal Proceedings of the Royal Society B.

A scanning electron microscope image of a dental platform element from the Conodont genus Sweetognathus, collected in Wyoming, USA. This specimen is between 293.7 and 294.9 years old. (Image: David Terrill, Charles Henderson)

One of the most convincing arguments proving the theory of evolution is that it is fairly easy to predict how animals and plants will evolve to adapt to changes in their habitats. There is no shortage of proof that organisms with a common ancestor evolve in the same way even if they are entirely isolated from each other. One of the most prominent examples is the Midas cichlid in Nicaragua. Approximately 6,000 years ago, individual fish colonised various crater lakes. Interestingly, they developed identical morphologies in their new habitats. One group specialised in catching small shrimps and developed a stocky body with a flat mouth. Another group hunts fish in deeper water and is considerably more streamlined. ‘These subspecies are found in each of the crater lakes, although there is no connection whatsoever between the habitats,’ says Dr. Emilia Jarochowska from GeoZentrum Nordbayern at FAU. ‘This is an example of parallel evolution.’

Fossils from Russia and Bolivia

Emilia Jarochowska’s research focuses on evolution in different ecosystems, but rather than studying animals which are still alive today she concentrates on conodonts, organisms which lived in the sea approximately 500 to 200 million years ago and were one of the first vertebrates. The cone-shaped teeth of the eel-like organisms can still be found as micro fossils in sedimentary rocks across the globe. Scientists estimate that there were roughly 3000 different species of conodonts. ‘Scientists have suspected for several years now that a certain subspecies known as Conodont Sweetognathus developed several parallel evolutionary adaptations,’ says Emilia Jarochowska.

The researchers from Erlangen set out with palaeontologists from the University of Calgary to prove this theory. The Canadian researchers had collected fossilised Sweetognathus teeth from various locations across the world, including Bolivia and Russia. Emilia Jarochowska explains, ‘As we now have such a good knowledge of tectonics over the history of the Earth, we can rule out the possibility that organisms from these regions were ever in contact with each other.’ The fossils measuring a mere two to three millimetres in length were scanned at GeoZentrum Nordbayern in a scanner with a spatial resolution of four micrometres, which delivers even higher definition pictures than a CT in a hospital. Precise 3D models and mathematical descriptions were made of more than 40 samples.

Parallel evolution confirmed

The painstaking analysis of the morphologies in the dental elements confirmed what scientists have suspected for years: Conodont Sweetognathus adapted repeatedly in response to different food sources after emigrating to new habitats in an almost identical fashion in spite of these habitats being isolated from each other. Comparing samples from a large number of fossils over a number of years has now allowed researchers to confirm without a doubt that the teeth found in Bolivia and Russia come from organisms with a common ancestor. ‘We were able to prove that two lineages of Sweetognathus in two different parts of the world followed the same developmental pattern,’ Emilia Jarochowska explains. ‘That is further proof for the theory of evolution – and for the effectiveness of international collaboration.’

References: W. Petryshen , C. M. Henderson , K. De Baets and E. Jarochowska, “Evidence of parallel evolution in the dental elements of Sweetognathus conodonts”, The Royal Society Publishing, 2020. https://royalsocietypublishing.org/doi/10.1098/rspb.2020.1922 https://doi.org/10.1098/rspb.2020.1922

Provided by FAU

Tiny Moon Shadows May Harbor Hidden Stores Of Ice (Planetary Science)

Hidden pockets of water could be much more common on the surface of the moon than scientists once suspected, according to new research led by the University of Colorado Boulder. In some cases, these tiny patches of ice might exist in permanent shadows no bigger than a penny.

“If you can imagine standing on the surface of the moon near one of its poles, you would see shadows all over the place,” said Paul Hayne, assistant professor in the Laboratory of Atmospheric and Space Physics at CU Boulder. “Many of those tiny shadows could be full of ice.”

In a study published today in the journal Nature Astronomy, Hayne and his colleagues explored phenomena on the moon called “cold traps”–shadowy regions of the surface that exist in a state of eternal darkness.

Many have gone without a single ray of sunlight for potentially billions of years. And these nooks and crannies may be a lot more numerous than previous data suggest. Drawing on detailed data from NASA’s Lunar Reconnaissance Orbiter, the researchers estimate that the moon could harbor roughly 15,000 square miles of permanent shadows in various shapes and sizes–reservoirs that, according to theory, might also be capable of preserving water via ice.

Future lunar residents, in other words, may be in luck.

“If we’re right, water is going to be more accessible for drinking water, for rocket fuel, everything that NASA needs water for,” said Hayne, also of the Department of Astrophysical and Planetary Sciences.

Visiting a crater

To understand cold traps, first take a trip to Shackleton Crater near the moon’s south pole. This humungous impact crater reaches several miles deep and stretches about 13 miles across. Because of the moon’s position in relation to the sun, much of the crater’s interior is permanently in shadow–a complete lack of direct sunlight that causes temperatures inside to hover at around minus 300 degrees Fahrenheit.

“You look down into Shackleton Crater or Shoemaker Crater, you’re looking into this vast, dark inaccessible region,” Hayne said. “It’s very forbidding.”

That forbidding nature, however, may also be key to these craters’ importance for planned lunar bases. Scientists have long believed that such cold traps could be ideal environments for hosting ice–a valuable resource that is scarce on the moon but is occasionally delivered in large quantities when water-rich comets or asteroids crash down.

“The temperatures are so low in cold traps that ice would behave like a rock,” Hayne said. “If water gets in there, it’s not going anywhere for a billion years.”

In their latest research, however, Hayne and his colleagues wanted to know how common such traps might be. Do they only exist in big craters, or do they spread over the face of the moon?

To find out, the team pulled data from real-life observations of the moon, then used mathematical tools to recreate what its surface might look like at a very small scale. The answer: a bit like a golf ball.

Based on the team’s calculations, the moon’s north and south poles could contain a tremendous number of bumps and knicks capable of hosting permanent shadows–many of them just a centimeter wide. Previous estimates pegged the area of cold traps on the moon at around 7,000 square miles, about half of what Hayne and his colleagues have predicted.

Mining for water

Hayne notes that his team can’t prove that these shadows actually hold pockets of ice–the only way to do that would be to go there in person or with rovers and dig.

But the results are promising, and future missions could shed even more light, literally, on the moon’s water resources. Hayne, for example, is leading a NASA effort called the Lunar Compact Infrared Imaging System (L-CIRiS) that will take heat-sensing panoramic images of the moon’s surface near its south pole in 2022.

If his team’s findings bear out, locating the ingredients for a hot shower on the moon may have just gotten a lot easier.

“Astronauts may not need to go into these deep, dark shadows,” Hayne said. “They could walk around and find one that’s a meter wide and that might be just as likely to harbor ice.”

References: Hayne, P.O., Aharonson, O. & Schörghofer, N. Micro cold traps on the Moon. Nat Astron (2020). https://doi.org/10.1038/s41550-020-1198-9 http://dx.doi.org/10.1038/s41550-020-1198-9

Provided by University Of Colorado At Boulder

This Transforming Rover Can Explore the Toughest Terrain (Planetary Science)

Made of a pair of two-wheeled vehicles, NASA’s DuAxel is designed to descend crater sides and near-vertical cliffs on the Moon, Mars, and beyond.

A rover trundles over rocky terrain, its four metal wheels clattering along until they encounter a seemingly insurmountable hazard: a steep slope. Down below is a potential trove of science targets. With a typical rover, the operators would need to find another target, but this is DuAxel, a robot built for situations exactly like this.

The DuAxel rover is seen here participating in field tests in the Mojave Desert. The four-wheeled rover is composed of two Axel robots. One part anchors itself in place while the other uses a tether to explore otherwise inaccessible terrain. Image credit: NASA/JPL-Caltech/J.D. Gammell

The rover is actually made of a pair of two-wheeled rovers, each called Axel. To divide and conquer, the rover stops, lowers its chassis and anchors it to the ground before essentially splitting in two. With the rear half of DuAxel (short for “dual-Axel”) firmly in place, the forward half undocks and rolls away on a single axle. All that connects the two halves now is a tether that unspools as the lead axle approaches the hazard and rappels down the slope, using instruments stowed in its wheel hub to study a scientifically attractive location that would normally be out of reach.

During the same field test, the DuAxel rover separates into two single-axled robots so that one can rappel down a slope too steep for conventional rovers. Image credit: NASA/JPL-Caltech/J.D. Gammell

This scenario played out last fall during a field test in the Mojave Desert, when a small team of engineers from NASA’s Jet Propulsion Laboratory in Southern California put the modular rover through a series of challenges to test the versatility of its design.

“DuAxel performed extremely well in the field, successfully demonstrating its ability to approach a challenging terrain, anchor, and then undock its tethered Axel rover,” said Issa Nesnas, a robotics technologist at JPL. “Axel then autonomously maneuvered down steep and rocky slopes, deploying its instruments without the necessity of a robotic arm.”

The two-wheeled Axel descends the slope while tethered to its counterpart anchored above the slope. The tether serves as a climbing rope of sorts while also providing power and a means of communication. Image credit: NASA/JPL-Caltech/J.D. Gammell

The idea behind creating two single-axle rovers that can combine into one with a central payload is to maximize versatility: The four-wheeled configuration lends itself to driving great distances across rugged landscapes; the two-wheeled version offers a nimbleness that larger rovers cannot.

“DuAxel opens up access to more extreme terrain on planetary bodies such as the Moon, Mars, Mercury, and possibly some icy worlds, like Jupiter’s moon Europa,” added Nesnas.

The flexibility was built with crater walls, pits, scarps, vents, and other extreme terrain on these diverse worlds in mind. That’s because on Earth, some of the best locations to study geology can be found in rocky outcrops and on cliff faces, where many layers of the past are neatly exposed. They’re hard enough to reach here, let alone on other celestial bodies.

The rover’s mobility and ability to access extreme locations is an enticing combination to Laura Kerber, a planetary geologist at JPL. “This is why I find the Axel rover to be quite delightful,” she said. “Instead of always trying to safeguard itself against dangers such as falling or flipping over, it is designed to withstand them.”

Video: A flexible rover that has both ability to travel long distances and rappel down hard-to-reach areas of scientific interest has undergone a field test in the Mojave Desert in California to showcase its versatility. Composed of two Axel robots, DuAxel is designed to explore crater walls, pits, scarps, vents and other extreme terrain on the moon, Mars and beyond. Credit: NASA/JPL-Caltech

A Two-Wheeled History

The radical concept of two robotic vehicles functioning as one has roots in the late 1990s, when NASA began exploring ideas for modular, reconfigurable, self-repairing rovers. This inspired Nesnas and his team at JPL to develop the robust, flexible two-wheeled robot that would come to be known as Axel.

They envisioned a modular system: Two Axels could dock to either side of a payload, for example, or three Axels could dock to two payloads, and so on, creating a “train” of Axels capable of transporting many payloads. This concept also fulfilled the “self-repairing” requirement of NASA’s challenge: Should one Axel fail, another could take its place.

Axel development remained focused on modular transportation until 2006, when satellite imaging of the Martian surface revealed gullies in crater walls. Later, the discovery of what appeared to be seasonal outflows of liquid water – dark features known as recurring slope lineae – heightened interest in using robots to take samples. Scientists wanted to know whether gullies and recurring slope lineaewere caused by water flows or something else.

But the slopes are too steep for a conventional rover – even for Curiosity or the soon-to-land Perseverance rover, both of which are designed to traverse slopes of up to 30 degrees. To explore these features directly would require a different kind of vehicle.

During warm seasons on Mars, dark streaks called “recurring slope lineae” often appear on crater slopes, as seen in this series of observations captured by the HiRISE camera aboard NASA’s Mars Reconnaissance Orbiter. The DuAxel rover is designed to rappel to such inaccessible areas to study them. Credit: NASA/JPL-Caltech/University of Arizona

So Nesnas and his team began developing a version of Axel that would be tethered to a lander, using the tether not just to descend a crater side or steep canyon wall, but also to supply power and communicate with the lander. Its wheels could be equipped with extra-high grousers, or treads, for added traction, while the wheel hubs could house microscopes, drills, sample-collection scoops, and other instrumentation to study the terrain. To turn, the two-wheeled axle would just rotate one of its wheels faster than the other.

Interest in the concept’s flexibility has led to a burgeoning family of two-wheeled designs, including NASA JPL’s A-PUFFER and BRUIE, which extend the possibility of exploration to new destinations and applications, including under water on icy worlds.

Despite the tethered Axel’s versatility, there was a notable limitation when used in conjunction with a stationary lander: The lander would need to be within rappelling distance of the crater side – demanding a degree of landing precision that may not be possible for a planetary mission.

To remove this requirement and boost mobility, the team reverted to the original modular design, adapted it to the new tethered Axel, and named it DuAxel.

“The key advantage of using DuAxel is made clear when you have landing site uncertainty, such as we do on Mars, or you want to move to a new location to rappel and explore with Axel,” said Patrick Mcgarey, a robotic technologist at JPL and DuAxel team member. “It enables untethered driving from the landing site and allows for temporary anchoring to the terrain because it is essentially a transforming robot made for planetary exploration.”

While DuAxel remains a technology demonstration and is waiting to be assigned a destination, its team will continue honing its technology; that way, when the time comes, the robot would be ready to roll where other rovers fear to tread.

Provided by NASA JPL

The Colorful Walls of an Exposed Impact Crater on Mars (Planetary Science)

Impact craters have been called the “poor geologists’ drill,” since they allow scientists to look beneath to the subsurface of a planet without actually digging down. It’s estimated that Mars has over 600,000 craters, so there’s plenty of opportunity to peer into the Red Planet’s strata – especially with the incredible HiRISE (High Resolution Imaging Science Experiment) camera on board the Mars Reconnaissance Orbiter which has been orbiting and studying Mars from above since 2006.

This beautiful image shows the interior of an impact crater in the Hellas Planitia region of Mars – just north of the gigantic Hellas impact basin located in the southern hemisphere of Mars. This nameless crater is about 6 to 7 kilometers wide in total, but this partial image shows about 1 km of width inside the crater wall. Partway down from the crater rim is a prominent bright layer of bedrock.

HiRISE can operate in visible wavelengths – the same as human eyes — but it also uses near-infrared wavelengths to obtain information on the mineral groups present.

A view of the interior of an impact crater on Mars shows prominent bright layer of bedrock. Credit: NASA/JPL/UArizona

The HiRISE team said the colors in this image are enhanced in infrared, and the data shows three distinct bedrock colors: yellow, light blue-green, and dark blue. The colors correspond to different types of rock that were deposited from the impact as nearly flat-lying sheets, perhaps a combination of lava flows and sediments.

The blue colors in HiRISE infrared often correspond to minerals like olivine and pyroxene that are common in lava. Other banded olivine-bearing layers also show up as yellow, which in some places have been partially or wholly altered to carbonate, giving it a green blue color, and light blue can correspond to iron or magnesium.

The HiRISE “swath” showing the complete image, along with the highlighted region inside the crater that includes the detail shown in the lead image. Credit: NASA/JPL/LPL/University of Arizona.

Over the years, HiRISE has photographed thousands of targeted swaths of Mars’ surface in unprecedented detail. HiRISE has captured such amazing things as avalanches, towering dust devils, and much more. From an altitude that varies from 200 to 400 kilometers (about 125 to 250 miles) above Mars, HiRISE acquires surface images containing individual, basketball-size (30 to 60 centimeters, or 1 to 2 feet wide) pixel elements, allowing surface features 4 to 8 feet across to be resolved. These high-resolution images provide unprecedented views of our neighboring planet.

This article is republished here from Universe Today under common creative licenses