One Feature Mars has That we Don’t: Polar Megadunes

For fans of astrophotography, Kevin M. Gill needs no introduction. Even if you’re not up on the latest astronomical news and developments, chances are you’ve still seen some of his images over the years. From beautiful artist renditions to breathtaking photographs of far-off planets, Gill has covered it all. Among the latest images available on his official Flickr page are pictures of a unique feature on Mars: the Chasma Boreale Megadunes!

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How Much Carbon Dioxide Snow Falls Every Winter on Mars?

Like Earth, Mars experiences climatic variations during the course of a year because of the obliquity of its rotational axis. This leads to the annual deposition/sublimation of the CO2 ice/snow, which results in the formation of the seasonal polar caps. Similarly, these variations in temperature result in interaction between the atmosphere and the polar ice caps, which has a seasonal effect on surface features.

On Mars, however, things work a little differently. In addition to water ice, a significant percentage of the Martian polar ice caps are made up of frozen carbon dioxide (“dry ice”). Recently, an international team of scientists used data from NASA’s Mars Global Surveyor (MGS) mission to measure how the planet’s polar ice caps grow and recede annually. Their results could provide new insights into how the Martian climate varies due to seasonal change.

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How Old is the Ice at Mars’ North Pole?

On Earth, the study of ice core samples is one of many methods scientists use to reconstruct the history of our past climate change. The same is true of Mars’ northern polar ice cap, which is made up of many layers of frozen water that have accumulated over eons. The study of these layers could provide scientists with a better understanding of how the Martian climate changed over time.

This remains a challenge since the only way we are able to study the Martian polar ice caps right now is from orbit. Luckily, a team of researchers from UC Boulder was able to use data obtained by the High-Resolution Imaging Science Experiment (HiRISE) aboard the Mars Reconnaissance Orbiter (MRO) to chart how the northern polar ice caps’ evolved over the past few million years.

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Another Incredible Picture of Mars, This Time From a Region Just Outside Valles Marineris

The Mars Reconnaissance Orbiter (MRO) delivers once again! Using its advanced imaging instrument, the High Resolution Imaging Experiment (HiRISE) camera, the orbiter captured a breathtaking image (shown below) of the plains north of Juventae Chasma. This region constitutes the southwestern part of Valles Marineris, the gigantic canyon system that runs along the Martian equator.

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This is the Spot Where ESA’s Schiaparelli Crashed Into Mars

On October 19th, 2016, the NASA/ESA ExoMars mission arrived at the Red Planet to begin its study of the surface and atmosphere. While the Trace Gas Orbiter (TGO) successfully established orbit around Mars, the Schiaparelli Lander crashed on its way to the surface. At the time, the Mars Reconnaissance Orbiter (MRO) acquired images of the crash site using its High Resolution Imaging Science Experiment (HiRISE) camera.

In March and December of 2019, the HiRISE camera captured images of this region once again to see what the crash site looked like roughly three years later. The two images show the impact crater that resulted from the crash, which was partially-obscured by dust clouds created by the recent planet-wide dust storm. This storm lasted throughout the summer of 2019 and coincided with Spring in Mars’ northern hemisphere.

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It Hasn’t Rained on Mars for a Long Time, but These Sand Dunes Look Like Raindrops, and They’re Filled with Chemicals Made in Water

Mars is well-known for being a dry and arid place, where dusty red sand dunes are prevalent and water exists almost entirely in the form of ice and permafrost. An upside to this, however, is the fact that these conditions are the reason why Mars’ many surface features are so well preserved. And as missions like the Mars Reconnaissance Orbiter (MRO) have shown, this allows for some pretty interesting finds.

Consider the picture recently taken by Curiosity’s High Resolution Imaging Science Experiment (HiRISE) instrument while orbiting above the Copernicus Crater on Mars. This image showed raindrop-like features that are actually signs of sand dunes that are rich in olivine. These same types of dunes exist on Earth but are very rare since this mineral weathers quickly and turns to clay in wet environments.

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Huge Sheets of Ice Found Hidden Just Beneath the Surface of Mars

Its an established fact that Mars was once a warmer and wetter place, with liquid water covering much of its surface. But between 4.2 and 3.7 billion years ago, the planet lost its atmosphere, which caused most of its surface water to disappear. Today, much of that water remains hidden beneath the surface in the form of water ice, which is largely restricted to the polar regions.

In recent years, scientists have also learned of ice deposits that exist in the equatorial regions of Mars, though it was unlcear how deep they ran. But according to a new study led by the U.S. Geological Survey, erosion on the surface of Mars has revealed abundant deposits of water ice. In addition to representing a major research opportunity, these deposits could serve as a source of water for Martian settlements, should they ever be built.

The study, titled “Exposed subsurface ice sheets in the Martian mid-latitudes“, recently appeared in Science. The study was led by Colin M. Dundas, a researcher with the U.S. Geological Survey, and included members from the Lunar and Planetary Laboratory (LPL) at the University of Arizona, Johns Hopkins University, the Georgia Institute of Technology, the Planetary Science Institute, and the Institute for Geophysics at the University of Texas at Austin.

Artists concept of the Mars Reconnaisance Orbiter (MRO). Credit: NASA/JPL

For the sake of their study, the team consulted data obtained by the High Resolution Imaging Science Experiment (HiRISE) aboard the Mars Reconnaissance Orbiter (MRO). This data revealed eight locations in the mid-latitude region of Mars where steep slopes created by erosion exposed substantial quantities of sub-surface ice. These deposits could extend as deep as 100 meters (328 feet) or more.

The fractures and steep angles indicate that the ice is cohesive and strong. As Dundas explained in a recent NASA press statement:

“There is shallow ground ice under roughly a third of the Martian surface, which records the recent history of Mars. What we’ve seen here are cross-sections through the ice that give us a 3-D view with more detail than ever before.”

These ice deposits, which are exposed in cross-section as relatively pure water ice, were likely deposited as snow long ago. They have since become capped by a layer of ice-cemented rock and dust that is between one to two meters (3.28 to 6.56 ft) thick. The eight sites they observed were found in both the northern and southern hemispheres of Mars, at latitudes from about 55° to 58°, which accounts for the majority of the surface.

It would be no exaggeration to say that this is a huge find, and presents major opportunities for scientific research on Mars. In addition to affecting modern geomorphology, this ice is also a preserved record of Mars’ climate history. Much like how the Curiosity rover is currently delving into Mars’ past by examining sedimentary deposits in the Gale Crater, future missions could drill into this ice to obtain other geological records for comparison.

At this pit on Mars, the steep slope at the northern edge (toward the top of the image) exposes a cross-section of a thick sheet of underground water ice. Credits: NASA/JPL-Caltech/UA/USGS

These ice deposits were previously detected by the Mars Odyssey orbiter (using spectrometers) and ground-penetrated radar aboard the MRO and the ESA’s Mars Express orbiter. NASA also sent the Phoenix lander to Mars in 2008 to confirm the findings made by the Mars Odyssey orbiter, which resulted in it finding and analyzing buried water ice located at 68° north latitude.

However, the eight scarps that were detected in the MRO data directly exposed this subsurface ice for the first time. As Shane Byrne, the University of Arizona Lunar and Planetary Laboratory and a co-author on the study, indicated:

“The discovery reported today gives us surprising windows where we can see right into these thick underground sheets of ice. It’s like having one of those ant farms where you can see through the glass on the side to learn about what’s usually hidden beneath the ground.”

These studies would also help resolve a mystery about how Mars’ climate changes over time. Today, Earth and Mars have similarly-tiled axes, with Mars’ axis tilted at 25.19° compared to Earth’s 23.439°. However, this has changed considerably over the course of eons, and scientists have wondered how increases and decreases could result in seasonal changes.

Artist’s impression of glaciers that may have existed on the surface of Mars in the past. Credit: NASA/Caltech/JPL/UTA/UA/MSSS/ESA/DLR Eric M. De Jong, Ali Safaeinili, Jason Craig, Mike Stetson, Koji Kuramura, John W. Holt

Basically, during periods where Mars’ tilt was greater, climate conditions may have favored a buildup of ice in the middle-latitudes. Based on banding and color variations, Dundas and his colleagues have suggested that layers in the eight observed regions were deposited in different proportions and with varying amounts of dust based on varying climate conditions.

As Leslie Tamppari, the MRO Deputy Project Scientist at NASA’s Jet Propulsion Laboratory, said:

“If you had a mission at one of these sites, sampling the layers going down the scarp, you could get a detailed climate history of Mars. It’s part of the whole story of what happens to water on Mars over time: Where does it go? When does ice accumulate? When does it recede?”

The presence of water ice in multiple locations throughout the mid-latitudes on Mars is also tremendous news for those who want to see permanent bases constructed on Mars someday. With abundant water ice just a few meters below the surface, and which is periodically exposed by erosion, it would be easily accessible. It would also mean bases need not be built in polar areas in order to have access to a source of water.

This research was made possible thanks to the coordinated use of multiple instruments on multiple Mars orbiters. It also benefited from the fact that these missions have been studying Mars for extended periods of time. The MRO has been observing Mars for 11 years now, while the Mars Odyssey probe has been doing so for 16. What they have managed to reveal in that time has provided all kinds of opportunities for future missions to the surface.

Further Reading: NASA, Science

Study of Martian Sedimentary Layers Reveals More About the Planet’s Past

As of 2016, Mars became the permanent residence of no less than eight robotic missions, a combination of orbiters, rovers and landers. Between extensive studies of the Martian atmosphere and surface, scientists have learned a great deal about the planet’s history and evolution. In particular, they have uncovered voluminous amounts of evidence that Mars once had flowing water on its surface.

The most recent evidence to this effect from the University of Texas at Austin, where researchers have produced a study detailing how water deposited sediment in Mars’ Aeolis Dorsa region. According to their research, this area contains extensive sedimentary deposits that act as a historical record of Mars, cataloguing the influence played by water-based erosion over time.

The study, titled “Fluvial Stratigraphy of Valley Fills at Aeolis Dorsa, Mars: Evidence for Base-Level Fluctuations Controlled by a Downstream Water Body“, recently appeared in the scientific journal GeoScienceWorld. Led by Benjamin D. Cardenas – a geologist with the Jackson School of Geosciences at the University of Texas at Austin – the team examined satellite data of the Aeolis Dorsa region to study the structure of sedimentary deposits.

MOLA Topographic Map of Aeolis Quadrangle (MC-23) on the planet Mars. Credit: USGS

For years, Aeolis Dorsa has been of interest to scientists since it contains some of the most densely-packed sedimentary layers on Mars, which were deposited by flowing water (aka. fluvial deposits). These deposits are visible from orbit because of the way they have undergone a process known as “topographic inversion” – which consists of deposits filling low river channels, then being exhumed to create incised valleys.

By definition, incised valleys are topographic lows produced by “riverine” erosion – i.e. relating to a river or riverbank. On Earth, these valleys are commonly created by rising sea levels, and then filled with sediment as a result of falling sea levels. As sea levels rise, the valleys are cut from the landscape as the waters move inland; and as the sea levels drop, retreating waters deposit sediment within them.

According to the study, this process has created an opportunity for geophysicists and planetary scientist to observe Mars’ geological record in three dimensions and across significant distances. As Cardenas told Universe Today via email:

“Sedimentary rocks in general record information about the environments under which they were deposited. Fluvial (river) deposits specifically record information about the way rivers migrated laterally, the way they aggraded vertically, and how these things changed over time.”

The dotted white arrow points to curved strata recording point bar growth and river migration while the black arrow shows topographically inverted river deposits outcropping as ridges (e.g., black arrow). Credit:

Here on Earth, the statigraphy (i.e. the order and position of sedimentary layers) of sedimentary rocks has been used by geologists for generations to place constraints on what conditions were like on our planet billions of years ago. It has only been in recent history that the study of sedimentary layers has been used to place constraints on what environmental conditions were like on other planetary bodies (like Mars) billions of years ago.

However, most of these studies have produced data that has been unable to resolve sedimentary packaging at the sub-meter scale. Instead, satellite images have been used to define large-scale stratigraphic relationships, such as deposition patterns along past water channels. In other words, the studies have focused on cataloging the existence of past water flows on Mars more than what has happened since then.

As Cardenas indicated, he and his team took a different approach, one which considered that Mars has experienced changes over the past 3.5 billion years. As he explained:

“In general, there has been the assumption that a lot of the martian surface is not particularly different than it was 3.5 billion years ago. We make an effort to demonstrate that the modern surface at our study area, Aeolis Dorsa, is the result of burial, exhumation, and un-equal erosion, and it can’t be assumed that the modern surface represents the ancient surface at all. We really try to show that what we see today, the features we can measure today, are sedimentary deposits of rivers, and not actual rivers. This is incredibly important to realize when you start making interpretations of your observations, and it is frequently a missed point.”

Perspective view of Reull Vallis based on images taken by the ESA’s Mars Express. Reull Vallis, a river-like structure, is believed to have formed when running water flowed in the distant martian past. Credit and Copyright: ESA/DLR/FU Berlin (G. Neukum)

For the sake of their research, Cardenas and his team used stereo pairs of high-resolution images and topographic data taken by the Context Camera (CTX) and the High Resolution Imaging Science Experiment (HiRISE) aboard the Mars Reconnaissance Orbiter (MRO). This data was then combined with the Integrated Software for Imagers and Spectrometers (ISIS) –  a digital image-processing package used by the U.S. Geological Survey (USGS) – and NASA’s Ames Stereo Pipeline.

These processed the paired images into high-resolution topographic data and digital elevation models (DEMs) which were then compared to data from the Mars Orbiting Laser Altimeter (MOLA) instrument aboard the Mars Global Surveyor (MSG). The final result was a series of DEMs that were orders of magnitude higher in terms of resolution than anything previously produced.

For all of this, Cardenas and his colleagues were able to identify stacking patterns in the fluvial deposits, noted changes in sedimentation styles, and suggested mechanisms for their creation. In addition, the team introduced a brand new method to measure the flow direction of the rivers that left these deposits, which allowed them to see how the landscape has changed over the past few billion years.

“The study shows there was a large body of water on Mars ~3.5 billion years ago, and that this body of water increased and decreased in volume slowly enough that river sedimentation had time to adjust styles,” said Cardenas. “This is more in line with slower climatic changes, and less in line with catastrophic hydrologic events. Aeolis Dorsa is positioned along hypothesized coastlines of an ancient northern ocean on Mars. It’s interesting to find coastal river deposits at Aeolis Dorsa, but it doesn’t help us constrain the size of the water body (lake, ocean, etc.)”

Nanedi Valles, a roughly 800-kilometre valley believed to be caused by ground-water outflow. Copyright ESA/DLR/FU Berlin (G. Neukum)

In essence, Cardenas and his colleagues concluded that – similar to Earth – falling and rising water levels in a large water body forced the formation of the paleo-valleys in their study area. And in a way that is similar to what is happening on Earth today, rivers that formed in coastal regions were strongly influenced by changes in water levels of a large, downstream water body.

For some time, it has been something of a foregone conclusion that the surface of Mars is dead, its features frozen in time. But as this study demonstrated, the landscape has undergone significant changes since it lost its atmosphere and surface water. These findings will no doubt be the subject of interest as we get closer to mounting a crewed mission to the Martian surface.

Further Reading: GSA, GeoScienceWorld

Best Photos Yet of the Mars Lander’s Demise

A closeup of the dark, approximately circular crater about 7.9 feet (2.4 meters) in diameter marking the crash of the Schiaparelli test lander on Mars. The photo was taken on October 25 by NASA's Mars Reconnaissance Lander (MRO). Credit:
A closeup of the dark, approximately circular crater about 7.9 feet (2.4 meters) in diameter that marks the crash of the Schiaparelli test lander on Mars. The new, higher-resolution photo was taken on October 25 by NASA’s Mars Reconnaissance Lander (MRO). A hint of an upraised rim is visible along the crater’s lower left side. The tiny white specks may be pieces of the lander that broke away on impact. The odd dark curving line has yet to be explained.  Credit: NASA/JPL-Caltech

What’s the most powerful telescope for observing Mars? A telephoto lens on the HiRise camera on the Mars Reconnaissance Orbiter that can resolve features as small as 3 feet (1-meter) across. NASA used that camera to provide new details of the scene near the Martian equator where Europe’s Schiaparelli test lander crashed to the surface last week.

The Schiaparelli test lander was protected by its heat shield as it descended through the Martian atmosphere at high speed. Credit: ESA
The Schiaparelli test lander was protected by its heat shield as it descended through the Martian atmosphere at high speed. Credit: ESA

During an October 25 imaging run HiRise photographed three locations where hardware from the lander hit the ground all within about 0.9 mile (1.5 kilometers) of each other. The dark crater in the photo above is what you’d expect if a 660-pound object (lander) slammed into dry soil at more than 180 miles an hour (300 km/h). The crater’s about a foot and a half (half a meter) deep and haloed by dark rays of fresh Martian soil excavated by the impact.

But what about that long dark arc northeast of the crater?  Could it have been created by a piece of hardware jettisoned when Schiaparelli’s propellant tank exploded? The rays are curious too. The European Space Agency says that the lander fell almost vertically when the thrusters cut out, yet the asymmetrical nature of the streaks — much longer to the west than east — would seem to indicate an oblique impact. It’s possible, according to the agency, that the hydrazine propellant tanks in the module exploded preferentially in one direction upon impact, throwing debris from the planet’s surface in the direction of the blast, but more analysis is needed. Additional white pixels in the image could be lander pieces or just noise.

This Oct. 25, 2016, image shows the area where the European Space Agency's Schiaparelli test lander reached the surface of Mars, with magnified insets of three sites where components of the spacecraft hit the ground. It is the first view of the site from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter taken after the Oct. 19, 2016, landing event and our highest resolution of the scene to date. Annotations by the author. Click for a full-resolution image. Credit: NASA/JPL-Caltech
This Oct. 25, 2016, image shows the area where the European Space Agency’s Schiaparelli test lander reached the surface of Mars, with magnified insets of three sites where components of the spacecraft hit the ground. It is the first view of the site from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter taken after the Oct. 19, 2016, landing event and our highest resolution of the scene to date. Click for a full-resolution image. Credit: NASA/JPL-Caltech

In the wider shot, several other pieces of lander-related flotsam are visible. About 0.8 mile (1.4 km) eastward, you can see the tiny crater dug out when the heat shield smacked the ground. Several bright spots might be pieces of its shiny insulation. About 0.6 mile (0.9 kilometer) south of the lander impact site, two features side-by-side are thought to be the spacecraft’s parachute and the back shell.  NASA plans additional images to be taken from different angle to help better interpret what we see.

The last happy scene for the lander when it still dangled from its chute before dropping and slamming into the surface. Credit: ESA
Schiaparelli dangles from its parachute in this artist’s view. A software error caused the chute to deploy too soon. Credit: ESA

The test lander is part of the European Space Agency’s ExoMars 2016 mission, which placed the Trace Gas Orbiter into orbit around Mars on Oct. 19. The orbiter will investigate the atmosphere and surface of Mars in search of organic molecules and provide relay communications capability for landers and rovers on Mars. Science studies won’t begin until the spacecraft trims its orbit to a 248-mile-high circle through aerobraking, which is expected to take about 13 months.

Everything started out well with Schiaparelli, which successfully transmitted data back to Earth during its descent through the atmosphere, the reason we know that the heat shield separated and the parachute deployed as planned. Unfortunately, the chute and its protective back shell ejected ahead of time followed by a premature firing of the thrusters. And instead of burning for the planned 30 seconds, the rockets shut off after only 3. Why? Scientists believe a software error told the lander it was much closer to the ground than it really was, tripping the final landing sequence too early.

Landing on Mars has never been easy. We’ve done flybys, attempted to orbit the planet or land on its surface 44 times. 15 of those have been landing attempts, with 7 successes: Vikings 1 and 2, Mars Pathfinder, the Spirit and Opportunity rovers, the Phoenix Lander and Curiosity rover. We’ll be generous and call it 8 if you count the 1971 landing of Mars 3 by the then-Soviet Union. It reached the surface safely but shut down after just 20 seconds.

Mars can be harsh, but it forces us to get smart.

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