Tag: Mars Reconnaissance Orbiter

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Using orbital data from Mars Reconnaissance Orbiter (MRO), scientists have found salt deposits on Mars where nearby crater counts suggest that the salt water that once held these deposits could have evaporated away as recently as 2.3 billion years ago.

Using [MRO’s] cameras to create digital elevation maps, Leask and Ehlmann found that many of the salts were in depressions – once home to shallow ponds – on gently sloping volcanic plains. The scientists also found winding, dry channels nearby – former streams that once fed surface runoff (from the occasional melting of ice or permafrost) into these ponds. Crater counting and evidence of salts on top of volcanic terrain allowed them to date the deposits.

Past data has suggested that if liquid surface water had existed on Mars, it was gone by three billion years ago.

You can read the scientists’ research paper here.. The maps to the right, figure two from the paper, shows the locations of discovered salt deposits, almost all of which are in the Martian southern cratered highlands of Mars.

Is there uncertainty in these results? My regular readers know that the answer is of course yes. The biggest problem for these Mars researchers is that, despite the surface evidence that liquid water should have once flowed on the surface of Mars, no scientist has yet come up with a satisfactory model of Mars’ past climate that would have made that possible. The planet was either too cold or had too thin an atmosphere, based on other data. And getting it warmer or with a thicker atmosphere involves inventing any number of scenarios that are all questionable, based on what is presently known.

There is also the increasing evidence that glaciers of ice, not water, might have carved those winding, dry channels. If so, many of the assumptions that liquid water existed might simply be wrong, or incomplete. The scientists who wrote this report recognize this importance of ice on Mars, and note in their abstract that

…we think that the water source came from surface runoff, rather than deep groundwater welling up to the surface. The small amounts of water required are most likely from occasional melting of ice.

As always, more data is needed, with the most useful data that will clarify these conclusions being that gathered by future colonists on the surface of Mars itself.

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Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken on November 4, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a small portion of the floor of a very ancient and eroded unnamed 40-mile-wide crater on Mars.

MRO’s science team labeled this picture simply as a “Fractured Feature.” The section I have focused on in the cropped image is clearly the fractures the scientists were interested in. What is heck caused this?

The location is at 39 degrees north latitude and is located at the very western end and in the center of the 2,000-mile-long mid-latitude strip I call glacier country because practically every photo exhibits evidence of glaciers. Thus, this fractured terrain is almost certainly evidence of ice that partly buried and thus protected from sublimating away.

The collapse feature indicates more, however. The circular shape of the fractures suggests that the center of this feature is sinking, with the ice on all sides slipping downward and breaking as it does so. The location however is not in the center of this crater, but near its southern interior rim. Moreover, in a wider image from MRO’s context camera this feature appears to be within what looks like a thick patch of ice filling most of the southeast quadrant of the crater. On it are other similar collapse features.

The data suggests that this ice patch is eroding, but doing so influenced by the rough terrain on which it sits. The sinks suggest the glacial ice is sublimating first over low spots, but this is hardly certain.

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Many features on Mars immediately make one think of the Grand Canyon and the stark dramatic geology of the American southwest. Today’s cool image on the right, cropped and reduced to post here, is a typical example. Photographed on September 7, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), it shows a dramatic cliff face that I estimate is about 3,000 feet high.

A closer look, however, almost always shows that this Martian terrain is not like the American southwest at all, but alien in its own way.

At the base of this abrupt cliff the terrain suddenly changes to a series of smooth downward fan-shaped flows. The cliff evokes rough boulders, avalanches, and chaotic erosion. The fans evoke a gentle and organized erosion of small particles like dust or sand. The two processes are completely different, and yet here the former is butted right up against the latter.

The fans also appear to flow out of hollows in the rough cliff, suggesting that somehow as the cliff erodes in chunks those chunks break into sand or dust, find the lowest points, and then flow downward like liquid.

How strange. How Martian. And how truly beautiful.

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Time for a cool image! The photo to the right, rotated, cropped, and reduced to post here, was taken on September 8, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a region of strangely sculptured terrain located several hundred miles south of Olympus Mons.

It appears the prevailing winds are to the west. The question is whether the wind is shaping a hard lava surface, over eons, or is shaping instead layers of dust or volcanic ash quickly and seasonally. At this location either is possible. In fact, we might even be seeing evidence of both at the same time.

The overview map below shows that the location is just outside the Medusae Fossae Formation, the largest volcanic ash deposit on Mars.
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Today’s cool image comes from today’s Mars Reconnaissance Orbiter’s (MRO) high resolution picture of the day, rotated and cropped to post here. The original was taken back on March 28, 2017.

What formed those strange circular ridges and the many small cracks and hollows? The caption provided is somewhat vague and I think confusing:

This formation looks like a crater from a meteor impact rather than an ancient caldera of a volcano. Connected to the crater is a carved-out area that resembles a lake bed. At high resolution, we might be able to determine the likelihood of a water lake bed or lava bed. This observation will give insight into some of the interesting geology of this area.

The crater this caption is referring to is not visible in the image provided. It can be seen to the west of this location, in the MRO context camera picture below.
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Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken on July 17, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the scientists label as an alluvial fan.

I have also seen them label this kind of avalanche as mass wasting, where the material moves down slope suddenly in a single mass.

The image shows the aftermath of such an event, after a large blob of material broke free from the mountainside and slid almost as a unit downhill to settle more than two miles away on the floor of the canyon. The distance traveled and the blobby nature of the flow both reveal how the lower Martian gravity changes the nature of such events, compared to what you might see on Earth. The flows can travel farther, and can hold together as a unit easier.

The overview map below not only provides the context, but it tells us that such events are remarkably common in this place.
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On Mars, one of the most common kinds of landscape is called chaos terrain. Made up of mesas, buttes, and cross-cutting random canyons, this geology is not seen on Earth, and when first identified by scientists in early orbital pictures in the 1970s, it baffled them. While it is clear that some form of erosion process caused it, the scientists did not have enough data then to figure out what that process was.

Today scientists have a rough theory, based on what they now know about Mars’ overall geology and its climate and orbital history. The canyons of chaos terrain were originally fault lines where either water or ice could seep through and widen. See this January 2020 post for a more detailed explanation.

Most of the cool images I have posted of chaos terrain have been in places in the mid-latitudes that are covered with glaciers. See for example this December 2019 post of one particular mesa in glacier country, with numerous glaciers flowing down its slopes on all sides. That mesa is quite typical of all such mesas in the mid-latitudes.

Today’s cool image above, cropped to post here, takes us instead to the Martian very dry equatorial regions. The photo was taken on May 17, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), and like mid-latitude chaos, it shows a collection of random mesas with canyons cut almost randomly between.

Unlike the mid-latitudes, however, there is no evidence of glaciers here. Instead, the canyons and mesa slopes are covered with dust, shaped into wind-blown dunes.

As always, the overview map below gives us some context.
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Today’s cool image is also today’s picture of the day from the science team of the high resolution camera on Mars Reconnaissance Orbiter (MRO. That picture, rotated, cropped, and reduced to post here, can be seen to the right. As the caption authors Sharon Wilson and Sarah Sutton write:

The smooth volcanic surfaces in the Gordii Fossae region are sometimes interrupted by long, narrow troughs, or fissures. These fissures form when underground faults, possibly involving magma movement, reach the near-surface, allowing material to collapse into pits or an elongated trough. This fissure appears to have erupted material that flowed onto the surface.

If you use your imagination, this trough resembles a gecko with its long tail and web-shaped feet!

This impression is even more evident in the wider image taken by MRO’s context camera below.
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Cool image time! The photo to the right, cropped and reduced to post here, was taken on May 30, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows the dusty dry floor of the chaos region of rough terrain in a side canyon of Valles Marineris, near its outlet. The color strip and the bright outcrops suggest that this terrain contains interesting minerals and resources. To determine exactly what those materials are however requires more information not available in this photo.

This ancient chaos terrain is the leftover eroded sea floor of a intermittent inland sea, leftover water from the catastrophic floods that are theorized to have flowed out of Valles Marineris and carved its gigantic canyons.

The overview map below shows this hypothesized sea.
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Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken on August 29, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the scientists label an “inverted channel in Arabia Terra,” a small example of the more than 10,000 miles of fossilized rivers in this region on Mars that scientists have identified using MRO.

They are made of sand and gravel deposited by a river and when the river becomes dry, the channels are left upstanding as the surrounding material erodes. On Earth, inverted channels often occur in dry, desert environments like Oman, Egypt, or Utah, where erosion rates are low – in most other environments, the channels are worn away before they can become inverted. “The networks of inverted channels in Arabia Terra are about 30m high and up to 1–2km wide, so we think they are probably the remains of giant rivers that flowed billions of years ago. [emphasis mine]

Since this fossilized river is located at 11 degrees north latitude, smack in the middle of the dry equatorial regions of Mars, it has certainly been a dry desert for a very long time. You can see how barren the terrain appears by looking at the wider view afforded by MRO’s context camera below.
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