Martian gullies flowing down to a Martian river of ice
Click for original image.
Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on May 16, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).
The scientists label this as “gullies previously identified in the walls of Harmakhis Vallis.” The gullies are obvious, the series of erosion features on the cliff wall. The cliff itself drops about 2,800 feet from the rim to the floor, and also appears to have internal horizontal layers that the gullies cut through.
What causes the gullies? Planetary scientists have a number of theories, none of which appear to explain the gullies everywhere on the Martian surface. They all appear in the mid-latitudes, where the most glaciers on Mars are found, and appear to be related to ice or frost freeze-thaw processes, with some gullies actually very ancient and formed when the planet’s rotational tilt was significantly different.
The white dot on the overview map to the right marks the location, on the north wall of Harmakhis Vallis, a long channel that flows 500 miles down into Hellas Basin, the death valley of the red planet. Harmakhis for most of its length appears to be filled with glacial ice, though it is unclear whether that ice is presently active or stationary. As indicated by the inset, at this point the channel narrows, which means the ice flow would have accelerated at this point, when it was active. That added motion would also be a contributing factor in creating the gullies.
In searching Behind the Black for background information on Harmakhis, I discovered that I featured an MRO image of this exact same cliff back in May 2023, though in that picture the shadows made it difficult to see the gullies. In that cool image I noticed the lack of debris at the bottom of the cliff, suggesting that it was probably carried away by the glacier when it was active. This fact strengthens the hypothesis that both the gullies and glacier are present static and unchanging.
The effort to image this cliff over time tells us that scientists are monitoring these gullies and the glacier for any changes. We will have to wait for their published papers to find out if any motion, as the resolution available here is not sufficient to tell.
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 or from any other book seller. If you want an autographed copy the price is $60 for the hardback and $45 for the paperback, plus $8 shipping for each. Go here for purchasing details. 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 May 16, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).
The scientists label this as “gullies previously identified in the walls of Harmakhis Vallis.” The gullies are obvious, the series of erosion features on the cliff wall. The cliff itself drops about 2,800 feet from the rim to the floor, and also appears to have internal horizontal layers that the gullies cut through.
What causes the gullies? Planetary scientists have a number of theories, none of which appear to explain the gullies everywhere on the Martian surface. They all appear in the mid-latitudes, where the most glaciers on Mars are found, and appear to be related to ice or frost freeze-thaw processes, with some gullies actually very ancient and formed when the planet’s rotational tilt was significantly different.
The white dot on the overview map to the right marks the location, on the north wall of Harmakhis Vallis, a long channel that flows 500 miles down into Hellas Basin, the death valley of the red planet. Harmakhis for most of its length appears to be filled with glacial ice, though it is unclear whether that ice is presently active or stationary. As indicated by the inset, at this point the channel narrows, which means the ice flow would have accelerated at this point, when it was active. That added motion would also be a contributing factor in creating the gullies.
In searching Behind the Black for background information on Harmakhis, I discovered that I featured an MRO image of this exact same cliff back in May 2023, though in that picture the shadows made it difficult to see the gullies. In that cool image I noticed the lack of debris at the bottom of the cliff, suggesting that it was probably carried away by the glacier when it was active. This fact strengthens the hypothesis that both the gullies and glacier are present static and unchanging.
The effort to image this cliff over time tells us that scientists are monitoring these gullies and the glacier for any changes. We will have to wait for their published papers to find out if any motion, as the resolution available here is not sufficient to tell.
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 or from any other book seller. If you want an autographed copy the price is $60 for the hardback and $45 for the paperback, plus $8 shipping for each. Go here for purchasing details. 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
Of interest
https://phys.org/news/2024-08-team-pixel-global-image-dataset.html
I still believe the gullies are caused by wind blown sand. Either blown off from above, or blown back up the hill from below, in a continuous erosion cycle.
It will be interesting to test the hypothesis by comparing these “lower altitude” erosion gullies with “higher altitude” which doesn’t have as much density in the wind to move sand grains.