The slowly changing dunes of Mars
In order to better understand the climate and geology of Mars, scientists need to study how the thin Martian atmosphere causes changes to the planet’s numerous sand dunes. To do this, they have been using the high resolution camera on Mars Reconnaissance Orbiter (MRO) to periodically snap photos of the same places repeatedly over time, to track any changes that might occur.
Recently the monthly download dump of images from MRO included one such location in the northwest quadrant of Hellas Basin, what I call the basement of Mars because it the planet’s lowest point. The uncaptioned image was taken on May 20, 2019 and was titled “Hellas Region Sand Dune Changes.” A review of past images shows that MRO has taken pictures of this location several times in the past, in 2011 and in 2017. All these images were taken during the Martian autumn season, and were taken to see if over time there were any significant changes to the dunes due to winds.
My superficial comparison of the 2011 and 2017 images does not show much obvious change. There could be small changes that my quick review did not spot, and there is also the strong possibility that the entire dune field could have shifted as a unit over those three Martian years, a change that would require a more detailed analysis beyond my technical capabilities. Click on both links, put the photographs in separate tabs, and switch quickly between them to see if you can spot any differences.
Comparing the 2011 and 2019 images however shows some significant changes, most of which I think are due to the 2018 global dust storm. Below is that comparison.
I have rotated, cropped, and reduced the images, plus stretched the 2011 photo, to create this matching comparison. The yellow arrows point to the same locations in each image, to help you orient yourself. Compared to the earlier image, the entire dune field is now covered with a new layer of material, much of it filling the low places between the dunes and thus reducing the overall elevation differences. In addition the new image shows a lot of dust devil tracks, not visible at all in the older image.
The dunes themselves however do not appear to have changed in any obvious way.
Some of these differences could be because the second image is taken at a slightly different angle, with the shadows less pronounced. That some dunes appear completely covered, and that some low spaces appear clearly filled, shows that lighting differences cannot explain all the changes. Moreover, that the darkest shadows in the second image match closely in size with the same shadows in the earlier images suggests that the lighting differences were not very substantial.
What these quick review suggests is that over a long time the big dunes at this location are relatively stable. They might slowly move with time, almost as a unit, and big events like a global dust storm can cover them with new deposits blown in from elsewhere, but the basic structure of the dune field appears to remain unchanged.
How that new material, deposited by the global dust storm, will change these dunes in the future remains unknown. Only time and more observations will tell us.
Readers!
Please consider supporting my work here at Behind the Black. Your support allows me the freedom and ability to analyze objectively the ongoing renaissance in space, as well as the cultural changes -- for good or ill -- that are happening across America. Fourteen years ago I wrote that SLS and Orion were a bad ideas, a waste of money, would be years behind schedule, and better replaced by commercial private enterprise. Only now does it appear that Washington might finally recognize this reality.
In 2020 when the world panicked over COVID I wrote that the panic was unnecessary, that the virus was apparently simply a variation of the flu, that masks were not simply pointless but if worn incorrectly were a health threat, that the lockdowns were a disaster and did nothing to stop the spread of COVID. Only in the past year have some of our so-called experts in the health field have begun to recognize these facts.
Your help allows me to do this kind of intelligent analysis. I take no advertising or sponsors, so my reporting isn't influenced by donations by established space or drug companies. Instead, I rely entirely on donations and subscriptions from my readers, which gives me the freedom to write what I think, unencumbered by outside influences.
You can support me either by giving a one-time contribution or a regular subscription. There are four ways of doing so:
1. Zelle: This is the only internet method that charges no fees. All you have to do is use the Zelle link at your internet bank and give my name and email address (zimmerman at nasw dot org). What you donate is what I get.
2. Patreon: Go to my website there and pick one of five monthly subscription amounts, or by making a one-time donation.
3. A Paypal Donation or subscription:
4. Donate by check, payable to Robert Zimmerman and mailed to
Behind The Black
c/o Robert Zimmerman
P.O.Box 1262
Cortaro, AZ 85652
You can also support me by buying one of my books, as noted in the boxes interspersed throughout the webpage or shown in the menu above.
In order to better understand the climate and geology of Mars, scientists need to study how the thin Martian atmosphere causes changes to the planet’s numerous sand dunes. To do this, they have been using the high resolution camera on Mars Reconnaissance Orbiter (MRO) to periodically snap photos of the same places repeatedly over time, to track any changes that might occur.
Recently the monthly download dump of images from MRO included one such location in the northwest quadrant of Hellas Basin, what I call the basement of Mars because it the planet’s lowest point. The uncaptioned image was taken on May 20, 2019 and was titled “Hellas Region Sand Dune Changes.” A review of past images shows that MRO has taken pictures of this location several times in the past, in 2011 and in 2017. All these images were taken during the Martian autumn season, and were taken to see if over time there were any significant changes to the dunes due to winds.
My superficial comparison of the 2011 and 2017 images does not show much obvious change. There could be small changes that my quick review did not spot, and there is also the strong possibility that the entire dune field could have shifted as a unit over those three Martian years, a change that would require a more detailed analysis beyond my technical capabilities. Click on both links, put the photographs in separate tabs, and switch quickly between them to see if you can spot any differences.
Comparing the 2011 and 2019 images however shows some significant changes, most of which I think are due to the 2018 global dust storm. Below is that comparison.
I have rotated, cropped, and reduced the images, plus stretched the 2011 photo, to create this matching comparison. The yellow arrows point to the same locations in each image, to help you orient yourself. Compared to the earlier image, the entire dune field is now covered with a new layer of material, much of it filling the low places between the dunes and thus reducing the overall elevation differences. In addition the new image shows a lot of dust devil tracks, not visible at all in the older image.
The dunes themselves however do not appear to have changed in any obvious way.
Some of these differences could be because the second image is taken at a slightly different angle, with the shadows less pronounced. That some dunes appear completely covered, and that some low spaces appear clearly filled, shows that lighting differences cannot explain all the changes. Moreover, that the darkest shadows in the second image match closely in size with the same shadows in the earlier images suggests that the lighting differences were not very substantial.
What these quick review suggests is that over a long time the big dunes at this location are relatively stable. They might slowly move with time, almost as a unit, and big events like a global dust storm can cover them with new deposits blown in from elsewhere, but the basic structure of the dune field appears to remain unchanged.
How that new material, deposited by the global dust storm, will change these dunes in the future remains unknown. Only time and more observations will tell us.
Readers!
Please consider supporting my work here at Behind the Black. Your support allows me the freedom and ability to analyze objectively the ongoing renaissance in space, as well as the cultural changes -- for good or ill -- that are happening across America. Fourteen years ago I wrote that SLS and Orion were a bad ideas, a waste of money, would be years behind schedule, and better replaced by commercial private enterprise. Only now does it appear that Washington might finally recognize this reality.
In 2020 when the world panicked over COVID I wrote that the panic was unnecessary, that the virus was apparently simply a variation of the flu, that masks were not simply pointless but if worn incorrectly were a health threat, that the lockdowns were a disaster and did nothing to stop the spread of COVID. Only in the past year have some of our so-called experts in the health field have begun to recognize these facts.
Your help allows me to do this kind of intelligent analysis. I take no advertising or sponsors, so my reporting isn't influenced by donations by established space or drug companies. Instead, I rely entirely on donations and subscriptions from my readers, which gives me the freedom to write what I think, unencumbered by outside influences.
You can support me either by giving a one-time contribution or a regular subscription. There are four ways of doing so:
1. Zelle: This is the only internet method that charges no fees. All you have to do is use the Zelle link at your internet bank and give my name and email address (zimmerman at nasw dot org). What you donate is what I get.
2. Patreon: Go to my website there and pick one of five monthly subscription amounts, or by making a one-time donation.
3. A Paypal Donation or subscription:
4. Donate by check, payable to Robert Zimmerman and mailed to
Behind The Black
c/o Robert Zimmerman
P.O.Box 1262
Cortaro, AZ 85652
You can also support me by buying one of my books, as noted in the boxes interspersed throughout the webpage or shown in the menu above.
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