Tag: geology

Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on November 18, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The science team labeled this image “Inverted Channel and Possible Lake Deposits.” The sharp razor-like butte, which I estimate is about 200 to 400 feet high, is an example of the several inverted channels in the full image. The serrated-edged flat plateau at the top of this picture, one of several in the full image, is an example of those possible lake deposits.

Why do the scientists think a lake might have once been here? Located at 8 degrees north latitude in the dry equatorial regions of Mars, there is almost certainly no near surface ice here now.

As always, the overview map provides the context, and a possible explanation.
» Read more

Click for original image.

Cool image time! The picture to the right, rotated and cropped to post here, was taken on December 31, 2022 by the high resolution camera on Mars Reconnaissance Orbiter.

The headline is pure silliness, and should not be taken seriously. However, the geological feature is intriguing nonetheless. Its almost perfect circular shape suggests a partly buried or eroded crater, except that its consistent thickness, almost like a wall, does not match what the rims of any crater should look like. Crater rims are made up of ejected material pushed out during impact, and thus always include some chaotic features.

My guess is that this circular feature is volcanic in nature. Maybe this was once a caldera, and the circle indicates a final vent from which lava extruded and then solidified.

At least, that’s my story.

The feature is located in the southwest quadrant of Hellas Basin, the basement of Mars, at 49 degrees south latitude. While this also suggests that ice might help explain this, we must also remember that much of the geology in that basin remains unexplained. Thus, there is no reason not to add one more feature to the list.

Click for original image.

Today’s cool image proves once again that you must never too quickly jump to any conclusions when you first look at a picture from space. The photo to the right, cropped, reduced, and sharpened to post here, was taken on November 24, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

At first glance it appears that those ridges are topped with patches of snow or frost. Not. What appears white in this black and white photo is immediately revealed to be light-colored dust in the color image.

According the label assigned to this image by the science team, these ridges represent layers, likely tilted steeply so that when exposed they form the layered cliff edges where that light dust has now gathered.

The overview map below provides further evidence that the white patches are dust, not snow.
» Read more

Click for original image.

Today’s cool image illustrates in some ways the uncertainty of science. The photo to the right, rotated, cropped, reduced, and sharpened to post here, was taken on December 1, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The science team intriguingly labeled it “Small Candidate Lake Deposit Downstream of Alluvial Fan.” I am not sure what they consider that lake deposit in the full image, so I have focused on the area of stucco-like ground, which resembles bedrock that has been corroded by some water process.

This area is just to the east of the central peaks of an unnamed 25-mile-wide crater in the southern cratered highlands. Many of the craters in this region are believed by scientists to have once harbored lakes formed by run-off from the glaciers that once existed on the craters’ inner rim. In this case it appears this stucco area is the head of an alluvial fan, coming down from the crater’s central peaks. You can see its beginning in this MRO high resolution image of the central peaks, taken in November 2016. As defined geologically,

An aluvial fan is an accumulation of sediments that fans outwards from a concentrated source of sediments, such as a narrow canyon emerging from an escarpment. They are characteristic of mountainous terrain in arid to semiarid climates, but are also found in more humid environments subject to intense rainfall and in areas of modern glaciation.

In this case the terrain is now arid, but shows evidence it once was icy wet.
» Read more

Click for full image.

Cool image time! The photo to the right, cropped to post here, was taken on October 31, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a small 4,000-foot-wide crater that is practically filled with a smooth, almost perfectly spherical mound, with the rest of the crater interior filled with sand dunes and what appears to be glacial debris.

Is that mound also glacial debris, covered with a layer of dirt and dust to protect it? If so, one wonders how the ice ended up in this shape. There are other craters with similar mounds in this region, all suggesting glacial debris but with the same question. Craters with lots of near surface ice in this region more often have a squishy blobby look.

Is the mound instead possibly mud, expressing the existence of a mud/ice volcano? If so, it shows no central pit or caldera, which is typical of such things.

Is it hardened sand? Martian dust that gets blown into craters generally gets trapped there, building up over time. If so, however, why does it have a smooth almost perfectly rounded shape? The ripple sand dunes surrounding it are more like what you would expect.

The small craters on the mound also tell us that it is hardened and old, no matter what it is made of.
» Read more

Click for full image.

Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken on December 5, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a collection of wormlike dunes located in the giant sea of dunes that surrounds the Martian north pole ice cap.

North is to the top. The season when this picture was taken was northern winter. The Sun is barely above the horizon, only 8 degrees high, and shining from the southeast. Because it is winter it is also dust season, making the atmosphere hazy and thus making the light soft. No distinct shadows, except that the sides of the dunes facing away from the Sun are darkly shadowed.

The consistent orientation of the dunes suggests that the prevailing winds blow from the northeast to create the steep-sided alcoves. The wind however might not be the only factor to form these dunes.
» Read more

Click for full image.

The photo to the right, cropped, reduced, and enhanced to post here, was taken on October 27, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The full photo was simply labeled as a “collapse feature”, and because it contained a few other sinks to the north beyond the top edge of this cropped picture, it is unclear if the scientists were referring to this sink in particular.

This sink is the most interesting however, because it really looks like something had sucked material out from below, causing the surface crust to fall downward, intact except for some cracks along the perimeter of the collapse.

The overview map below as always provides some context that might explain what we are seeing.
» Read more

Click for full image.

Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken on October 2, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a cluster of craters filled with ripple dunes.

The color strip tells us something [pdf] about the surface materials here. The reddish-orange in the craters is thought to be dust. The greenish terrain above the craters is likely coarse rock or bedrock, covered with a veneer of dust.

There is no ice here, just dust that over time has become trapped in the craters and cannot escape. And though there is also dust on the surrounding terrain, there is not that much. The craters themselves are likely very ancient, based on their shape and the eroded condition of their rims.

» Read more