The inexplicable behavior of Martian dust devils
Click for original image.
Today’s cool image illustrates the puzzling inclination of Martian dust devils to strongly favor specific regions on the Martian surface, for reasons that at present no one can confidently explain.
The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on June 28, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a plethora of dust devil tracks, almost all of which have an east-west orientation. Moreover, the tracks seem uninfluenced by the surface topography, continuing on their path without deviation, even as they cross cliffs, craters, and mounds. The orientation tells us the direction of the prevailing winds, though I don’t know if those winds blow to the east or to the west.
What makes this image revealing is that a gathering of such dust devil tracks is seen so rarely in other MRO high resolution photographs. I look at a lot of MRO pictures, and though dust devil tracks are not rare, most images don’t show this many. Apparently, there are specific conditions on Mars that cause a lot of tracks to appear in specific locations, either because atmospheric conditions create a lot more dust devils, or the ground conditions allow the tracks to become more visible.
On the overview map to the right the black dot marks this location, near the transition from the southern cratered highlands and Arabia Terra, the largest region between those cratered highlands and the northern lowland plains.
The inset illustrates the cratered nature of this region. It is not dissimilar to the cratered regions all across the southern hemisphere of Mars. And yet, here we see lots of dust devil tracks that we do not see elsewhere.
I have posted several previous cool images focused on locations where dust devils like to concentrate. In one case, posted in December 2019, some aspect of the ground itself attracts the devils, which act to clear off the dust from the surface so that any visible tracks there are very temporary.
In another case, from March 2019, the tracks appear to be more permanent. Here the dust devils appear to congregate along the crest of a ridge, and have been doing so for at least a decade. Why however remains unknown.
A third location was highlighted in December 2022. Once again some of the tracks seem to be concentrated along a ridge, but there are numerous other tracks scattered across the terrain as well.
What makes these particular images interesting is that they are the exception that proves the rule. Generally, MRO images of the Martian surface show comparably fewer dust devil tracks, usually none at all. Even in very dusty regions, such as the Medusae Fossae Formation (the largest volcanic ash deposit on Mars), the number of tracks is few or none.
This remains an open question about Mars, its atmosphere, and its weather conditions. Don’t expect an answer however until humans are roaming the red planet, doing in situ research in many different places.
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 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.
Today’s cool image illustrates the puzzling inclination of Martian dust devils to strongly favor specific regions on the Martian surface, for reasons that at present no one can confidently explain.
The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on June 28, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a plethora of dust devil tracks, almost all of which have an east-west orientation. Moreover, the tracks seem uninfluenced by the surface topography, continuing on their path without deviation, even as they cross cliffs, craters, and mounds. The orientation tells us the direction of the prevailing winds, though I don’t know if those winds blow to the east or to the west.
What makes this image revealing is that a gathering of such dust devil tracks is seen so rarely in other MRO high resolution photographs. I look at a lot of MRO pictures, and though dust devil tracks are not rare, most images don’t show this many. Apparently, there are specific conditions on Mars that cause a lot of tracks to appear in specific locations, either because atmospheric conditions create a lot more dust devils, or the ground conditions allow the tracks to become more visible.
On the overview map to the right the black dot marks this location, near the transition from the southern cratered highlands and Arabia Terra, the largest region between those cratered highlands and the northern lowland plains.
The inset illustrates the cratered nature of this region. It is not dissimilar to the cratered regions all across the southern hemisphere of Mars. And yet, here we see lots of dust devil tracks that we do not see elsewhere.
I have posted several previous cool images focused on locations where dust devils like to concentrate. In one case, posted in December 2019, some aspect of the ground itself attracts the devils, which act to clear off the dust from the surface so that any visible tracks there are very temporary.
In another case, from March 2019, the tracks appear to be more permanent. Here the dust devils appear to congregate along the crest of a ridge, and have been doing so for at least a decade. Why however remains unknown.
A third location was highlighted in December 2022. Once again some of the tracks seem to be concentrated along a ridge, but there are numerous other tracks scattered across the terrain as well.
What makes these particular images interesting is that they are the exception that proves the rule. Generally, MRO images of the Martian surface show comparably fewer dust devil tracks, usually none at all. Even in very dusty regions, such as the Medusae Fossae Formation (the largest volcanic ash deposit on Mars), the number of tracks is few or none.
This remains an open question about Mars, its atmosphere, and its weather conditions. Don’t expect an answer however until humans are roaming the red planet, doing in situ research in many different places.
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 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
Rotation of the planet causes Coriolis movement of the air, which is in conflict with the cold denser air descending from the plateau above. As they collide, it creates current eddies similar to whirlpools in water….
Na, I just made that up.
It could just as easily be higher air density being funneled pass the large Impact Craters Mountain range on one side and the higher terrain on the other side. The two air flows may have a different pH resulting in a ion exchange reaction resulting in a spinning vortex until the energy is spent…
Or the direct ionizing sunlight on the equator imparting an electrical charge to the dust, similar to a balloon rubbed on your hair, creating lift with a high electrical charge resulting in a magnetic Taurus that causes air to move driven by opposite charges on the ground.
Na, I made that up to.
I am intrigued and perplexed. I’ve played in many large dust devils in the desert as a kid, even tried a bedsheet to see if it would lift me in the air… It would just knock me off balance throwing me this way and that, with sand in my eyes.
Not all the trails go the same way, some even making U-turns. Others using hills like ski jumps but not landing on the other side where the trails disappear. Some trails follow the contour of the land like they lazily move extremely slow, while others follow straight lines through and over obstacles without deviation. The larger trails have arcing castoffs indicating the direction they are moving and the direction of the spin.
I thought I had it figured out until I saw two of the trails with castoffs in the opposite directions (opposite spin) moving towards each other creating a dust cast off basket weave before they merged. Beautiful.
I suppose because mars does not have a magnetic field, the spin of the dust devils will not all be the same.
I will also note the unusual amount of “splat” meteor Impacts. especially the smaller ones… The hot meteors appear to hit the ground creating a foam that raises unusually high resulting in ant hill formations. The soil in this area is odd, low water table or something.
I have to keep reminding myself, “this is another planet!”
Thank you for posting these, I find myself spending time that I don’t have scanning every foot looking for Waldo. (meaning anything out of the ordinary)
Loved that: “Na, I made that up”
I used to get in dust devils too.
The 1998 Oak Grove tornado exhibited ground rowing on hill slopes. Grand Island and El Reno had “A” and “U” shaped tracks.
Vorticity has always interested me.
. . . some aspect of the ground itself attracts the devils, . . .
If you really want to attract whirlwinds, put up a mobile home. Works great in Florida.
The only reason I can imagine for the dust devils to not be easily deviated by topography is they have higher altitude support, meaning the vortex goes invisibly higher up than the dust. In that case the ground would be less of a factor.
Allan: Good point. However, if the ground is less of a factor, then how do we explain the phenomenon I describe in this post where the evidence suggests that the dust devils specifically favor certain areas of ground?
The dark splotches on Mars: Magnets for dust devils