Tag: Mars Reconnaissance Orbiter

Today we have two cool images, both giving us a tiny glimpse at what it is like in the middle of summer on the fringes of Mars’ south pole ice cap. Their location is indicated by the blue crosses on the overview map on the right.

To review, the south pole on Mars is, like its north pole, mostly made up of a permanent icecap of water. In the south, this icecap is mostly mixed with dust and debris in the area outlined in black and dubbed the layered deposits. On top of this is a smaller thick water ice cap, indicated by light blue, which is in turn topped by a thin cap of frozen carbon dioxide, or dry ice, indicated by white. During the winter the entire pole, down to 60 degrees latitude also gets covered by a temporary mantle of dry ice, that sublimates away each spring.

Now for our cool images!
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Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken on September 30, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

It shows one half of what scientists have dubbed a pollywog crater, in which there is a single breach in the crater wall, aligned with the low point in the crater’s floor. Such craters suggest that they were once water- or ice-filled, and that they drained out through the breach either quickly in a single event or slowly over multiple events.

The second image below was taken by the wide angle context camera on MRO, and not only shows this entire crater, but several other adjacent craters, all of which show evidence of glacial fill in their interiors. The latitude here is 34 degrees south, placing these craters within the mid-latitude bands where such glacial features have been found by scientists in great numbers.
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Today’s cool image is actually a bunch, all found recently in the monthly image download from the high resolution camera on Mars Reconnaissance Orbiter (MRO).

All the photos I post below show pimple-like cones, all of which appear to be a type of small volcano. The cones are found in a wide range of locations, from the northern lowland plains to the cratered highlands to the mid-latitude transition zone between the two. They are also found at the bottom of deep canyons, in the floors of craters, and amidst mountains.

Let us begin.
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Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on October 25, 2020. It shows what it calls a “possible volcanic vent east of Olympus Mons”.

Is this active? If not, how old is it. Also, the elongated shape of the vent suggests the possibility of a lava tube, or at least some underground complexity to the release of its magma.

In order to get some clarity, I emailed Sarah Sutton of the Lunar and Planetary Laboratory of the University of Arizona, who requested this photograph. Her response:

The image is of a small shield volcano with an elongated vent at the summit. We don’t have complete stereo here yet, so we can’t tell exactly what the height is. This vent might have sourced tube-fed flows, but in this case, we can’t resolve such features in the image data. This and other small shield volcanoes in the vicinity are partially buried by plains-forming lava flows. The lava flows around the base overlap the flows that emanate radially from the summit vent. Therefore we infer that the shield is older than the surrounding lava flows.

The vent, which runs from the southwest to the northeast, sits on top of a sloping wide hill, which is that small shield volcano described by Sutton. The flat plains surrounding this hill are from later eruptions from other and possibly larger volcanoes. The wider overview map below might give us a clue as to the source.
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Scientists using the radar instrument on Mars Reconnaissance Orbiter (MRO) have now confirmed that the Martian glacial features that most resemble the glaciers seen on Earth are made of substantial amounts of ice, and were possibly active and growing only a few million years ago.

“Our radar analysis shows that at least one of these features is about 500 meters thick and nearly 100 percent ice, with a debris covering at most ten meters thick,” said Berman, lead author of “Ice-rich landforms of the southern mid-latitudes of Mars: A case study in Nereidum Montes” published online in Icarus at https://doi.org/10.1016/j.icarus.2020.114170. PSI scientists Frank C. Chuang, Isaac B. Smith and David A. Crown are co-authors on the paper.

Global mapping of Viscous Flow Features (VFFs), a general grouping of ice-rich flow features in the southern hemisphere of Mars shows a dense concentration in Nereidum Montes, along the northern rim of Argyre basin. Located within a northwestern subregion of Nereidum Montes is a large number of well-preserved VFFs and ice-rich mantling deposits, the paper says, potentially the largest concentrations of any non-polar region in the southern hemisphere.

…Processed data from the Shallow Radar (SHARAD) instrument aboard NASA’s Mars Reconnaissance Orbiter spacecraft were used to search for basal reflections across VFFs within the region. For one in particular, these observations and analysis indicate that it is composed of nearly pure water ice. Model ages obtained from crater counts and their associated size-frequency distributions (SFDs) on both ice-rich mantling deposits and small lobate VFFs suggest that the deposits stabilized several to tens of millions of years ago in the Late Amazonian Epoch, and that small lobate VFFs likely formed due to the mobilization of mantling deposits.

This data here reinforces the impressions from many other places within the 30-60 degree latitude bands on Mars where many such features are found.

Mars might be a desert, but it is a desert like Antarctica, not the Sahara. Any settlement there must use the Earth’s south pole as its guide for construction and design.

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Today’s cool image to the right, cropped and reduced to post here, is intriguing for a number of reasons. Taken on September 11, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), it shows a partially buried crater found in the middle of Hellas Basin, the lowest point on Mars and what I like to call the red planet’s basement.

What makes this crater intriguing is the layered pile of material filling its interior. If I didn’t know any better, I would think some construction crew has used a bulldozer to push debris from the crater’s right half in order to smooth the ground in preparation for building a strip mall, office building, or housing development.

This of course is not what happened. Then what did create those layered piles in the crater’s left half?
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Cool image time! The photo to the right, rotated and cropped to post here, was taken on September 27, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what is likely a crater that is partly buried by ice and dust and sand near or on the edge of Mars’s south polar ice cap.

It also shows an example of what planetary scientists have dubbed “cryptic terrain,” found generally on the margins of that ice cap. In this case, the location is on a plateau adjacent to the ice cap dubbed Promethei Planum. Despite a lot of searching, I could not locate any research papers describing Promethei Planum, though data outlined in one Mars Express press release from 2008 suggested it was part of the polar ice cap more than two miles thick that is covered by a thin mantle of dry ice each winter.

The strange curlicue cliffs and plateaus seen here are thought to form as part of the arrival and then sublimation away of that seasonal dry ice mantle, but how that process exactly works to create these particular geological features remains I think a mystery. North is to the top. The general grade is also downhill away from the icecap to the north.

Moreover, the overview map below, with the location of this image indicated by the blue cross, illustrates more mysteries.
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Cool image time! The photo to the right, cropped and reduced to post here, was taken on October 26, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It is what the camera team calls a “terrain sample,” meaning it was not specifically requested by a researcher but was instead chosen by the camera team because they need to regularly take images to maintain the camera’s temperature. When they do this, they try to pick a location that hasn’t been photographed in high resolution previously, and that might have some interesting features. Sometimes the photo is boring. Sometimes they hit pay dirt.

In this case, the photo captured an small impact crater, about 1,300 feet across, surrounded by a spray of secondary impacts. The color portion of the image shows what I suspect are dust devil tracks cutting across a surface that, because of its blue tint, is either rough or has frost or ice within it. At 48 degrees north latitude, the possibility of the latter is high, especially because this location is northwest of the Erebus mountains, where SpaceX has its prime Starship candidate landing zone and where scientists suspect ice is readily available very close to the surface. The overview map below shows this context.
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Cool image time! The photo to the right, cropped and reduced to post here, was taken on August 15, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a truly strange bunch of blocks beside a clean flow neatly organized in almost straight parallel lines.

What is going on? This location is at 38 degrees south latitude, a latitude where scientists have found a lot of features that resemble water ice glaciers, generally protected from sublimating away by a thin layer of dust and debris.

A first guess is that the smooth glacial flow at the lower right is disturbing the glacial material next to it, causing it to rip apart and break up. At the same time, the hollowed look of these glacial blocks suggests that the ice below that protective debris layer is also slowly sublimating away, causing the surface to sink.

The wider shot below helps confirm this impression.
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Cool image time! The photo to the right, cropped and reduced to post here, was taken on August 9, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Uncaptioned, the image is merely dubbed a “knob field.”

I won’t spend much time trying to explain this geology. It might be related to pedestal craters, but these ridges and mesas don’t really look like those features, since they don’t really stand above the surrounding terrain.

Maybe they are a very ancient field of craters long buried, now partly exposed due to erosion, but also partly buried by wind-blown Martian sand and dust. Once again, that many of their shapes don’t resemble craters discounts this explanation.

The location of this photo is in the southern cratered highlands, as shown by the black cross in the overview map below.
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Cool image time! The photo to the right, cropped and reduced to post here, was taken on July 1, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a very puzzling terraced mesa inside an enclosed depression or sinkhole (the western half of which can be seen in the full image).

What caused that mesa? A first scan of the image and the data suggests we are looking at sinkage related to the melting of an underground ice table. The latitude here is 34 degrees south, just far enough away from the equator for glacial activity to be possible. Moreover, the small circular depression in the upper right of the image strongly suggests an impact crater into slushy material. The implication is that this depression is the result of the melting or sublimation of underground ice, leaving behind a mesa that is made of solider stuff.

Another possibility is that the terraced mesa is actually the remains of glacial material. In the full image features inside other nearby depressions are terraced also, but are also much more reminiscent of glacial features found in many craters in the mid-latitudes. The depression is also close to the headwaters of Reull Valles, a meandering canyon where many images have shown glacial features (see for example here, here, and here).

These features however could also have nothing to do with water ice.
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Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken on August 12, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what to any Earthling’s eye appears to be a somewhat ordinary flat-topped mountain peak with two major flanking ridgelines descending downward to the north and the south, and two minor ridgelines descending to the northwest and southwest.

This peak and its landscape would surely be quite a spectacularly place to visit, should humans ever settle Mars and begin doing sightseeing hikes across its more interesting terrain. I can definitely imagine hiking trails coming up the two minor ridges, with a crest trail traversing the main north-south ridge across the peak.

This is not however a mountain on Earth. It is on Mars, which makes its formation and evolution over time fundamentally different than anything we find on Earth, despite its familiar look.

First, what formed it? Unlike most of Earth’s major mountain chains, the mountains of Mars were not formed by the collision of tectonic plates, squeezing the crust upward. Mars does not have plate tectonics. Most of its mountains formed either from the rise of volcanoes at single hot spots, or from the wearing away of the surrounding terrain to leave behind a peak or mesa.
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Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken on June 24, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a distinctive mesa in a mountainous region in the cratered highlands of Mars, just north of Hellas Basin, the deepest basin on the red planet.

The mesa’s most distinctive feature are its terraced layers, a feature that MRO has found in numerous other places surrounding and inside Hellas Basin (see for example the cool images here, here, here, here, here, and here.)

On Earth the assumption would be that these terraced layers imply different sedimentary layers that erode at different rates, as best illustrated by the Grand Canyon in Arizona. On Mars that assumption is not unreasonable, but unlike Earth, those layers could not have been formed in connection with large ocean bodies creating seafloor layers from the deposit of sealife over centuries. Some other geological process over time formed them, with volcanism, either from volcanoes or impact, being the most likely.
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