Gullies on a crater wall in the icy north of Mars
Click for original image.
Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on July 4, 2025 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows the lower right quadrant of a five-mile-wide unnamed crater in the high northern mid-latitudes of Mars.
The science team in its label for this picture focuses on the gullies visible on the crater’s interior wall. To my Earth-bound eye, these gullies look like recent erosion caused by underground ice sublimating into gas, causing the surface to collapse downward into the crater. This however is a purely uneducated guess.
The floor of the crater however shows features that resemble glacial fill, seen in numerous high latitude craters on Mars. This is not surprising, as the crater is located at 59 degrees north latitude, close enough to the pole for there to be a lot of near surface ice to be present.
The white dot on the overview map to the right marks the location, on the far north edge of Utopia Basin, one of several of Mars’ very large ancient impact basins.
At this latitude the entire surface of the terrain looks as if it is shaped by the presence of a near surface ice sheet. For example, in the inset we can see a large splash apron surrounding this crater, as if the impact had landed on ground impregnated with ice that quickly melted, splashed outward, and then refroze.
In the case of the gullies, researchers are still trying to figure out the geological processes that form them. They are found in many places in the Martian mid-latitudes. While initially believed to be related to the sublimation of underground ice, more recent research suggests they are formed by the seasonal dry ice frost cycle that in the high latitudes has carbon dioxide condense to fall as snow in autumn and then sublimate away in the spring.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The print edition can be purchased at Amazon. from any other book seller, or direct from my ebook publisher, ebookit.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
Click for original image.
Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on July 4, 2025 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows the lower right quadrant of a five-mile-wide unnamed crater in the high northern mid-latitudes of Mars.
The science team in its label for this picture focuses on the gullies visible on the crater’s interior wall. To my Earth-bound eye, these gullies look like recent erosion caused by underground ice sublimating into gas, causing the surface to collapse downward into the crater. This however is a purely uneducated guess.
The floor of the crater however shows features that resemble glacial fill, seen in numerous high latitude craters on Mars. This is not surprising, as the crater is located at 59 degrees north latitude, close enough to the pole for there to be a lot of near surface ice to be present.
The white dot on the overview map to the right marks the location, on the far north edge of Utopia Basin, one of several of Mars’ very large ancient impact basins.
At this latitude the entire surface of the terrain looks as if it is shaped by the presence of a near surface ice sheet. For example, in the inset we can see a large splash apron surrounding this crater, as if the impact had landed on ground impregnated with ice that quickly melted, splashed outward, and then refroze.
In the case of the gullies, researchers are still trying to figure out the geological processes that form them. They are found in many places in the Martian mid-latitudes. While initially believed to be related to the sublimation of underground ice, more recent research suggests they are formed by the seasonal dry ice frost cycle that in the high latitudes has carbon dioxide condense to fall as snow in autumn and then sublimate away in the spring.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The print edition can be purchased at Amazon. from any other book seller, or direct from my ebook publisher, ebookit. The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
Hi Bob… I can only agree with your analysis here….. ( I have to do some research on why we never see liquid CO2.. but I can do that myself when it occurs to me and I have time)
I have a question for you which I cannot recall if you have an opinion on.. in very many deep surface features on Mars ( valleys, craters, and such ) there is a dark layer in the strata, not so far down and visible almost everywhere on the planet. It seems to me that almost all the “dark streaks” originate from this layer. I know the current best guess is CO2 lumps sliding down the slope while sublimating, but why the dark layer? And why would it be dry ice rich?
You probably have more experience looking at random interesting images of Mars than anyone alive, I am very interested in your opinion, and if you ( or anyone else ) have any theories… I have given it a lot of thought and only drawn blanks.
Lee S: It is a a mistake to assume only one dark layer throughout the planet. Nor should you assume the dark streaks are from it.
There are many dark and light layers in the innumerable bedding planes that rover and orbital images have discovered all across the planet. The different shades likely relate to the nature of material coming from volcanic eruptions that placed layers on the surface.
Until we go there we will not be able to properly map out this eruption history. Once there however we should be able to create a reasonably detailed timeline for almost all of Martian history. Unlike Earth, the geology on Mars is not covered with life, and the atmosphere doesn’t change things as quickly or as drastically. And there are no oceans.
I agree that we really need some boots on the ground to sample and analyse the strata… With little history of water and no tectonic activity it should be pristine… Oh to be able to pull a long core sample up! But I still stand by my observation that there seems to be a fairly thin narrow dark band in most craters, not so far from the surface, a few 10’s of meters… And it seems consistent pretty much on all photos I have had a good look at. Perhaps this dark layer originates from a period of unusual activity certainly, but I have definitely noticed the dark streaks seem to mostly originate from around this layer.
Perhaps this is just my mind finding patterns where there are non… But every time I see a new picture of crater walls or valleys the phenomenon jumps out at me.