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Linear sand dunes in the Proctor crater, seen by Mars reconnaissance orbiter (MRO) on June 10, 2007. Image via NASA / JPL / University of Arizona.
Like the Earth, Mars has many sand dunes, but scientists are now learning that the processes involved in their formation and movement can be very different from what is happening on our own planet. A team of planetary scientists from the University of Arizona (UA) conducted the most detailed study ever done on how sand is moving on Mars and on the difference between this movement and the movement of sand in the deserts of the Earth.
The new research was led by Matthew Chojnacki at the Lunar and Planetary Laboratory (LPL) of AU and the peer-reviewed results were published in the current issue of the journal. Geology March 11, 2019.
The team discovered that the processes do not The movement of sand on Earth plays a very important role in the way sand is transported to Mars, including large-scale features of the landscape and differences in surface temperature of terrain. As Chojnacki explained:
Because there are large sand dunes in different parts of Mars, these are good places to look for changes … If you do not move sand, it means the surface is just sitting there and is bombarded by ultraviolet and gamma rays that destroy complex molecules and all ancient Martian biosignatures.
Another amazing set of sand dunes, large and small, in Proctor Crater on Mars, seen by MRO on February 9, 2009. Image via NASA / JPL / University of Arizona.
It may seem surprising that Mars even has sand dunes because its atmosphere is so thin – about 0.6% of sea level atmospheric pressure at sea level – but this is the case, and they can to go from a few feet to hundreds of feet. They have been seen from a spacecraft in orbit and very close to the ground by rovers. However, sand dunes on Mars move much more slowly, about two feet per year (about one Martian year), while sand dunes on Earth can migrate up to 100 feet per year. According to Chojnacki:
On Mars, there is simply not enough wind energy to move a significant amount of material to the surface. It may take two years on Mars to see the same movement that you usually see during a season on Earth.
Researchers wanted to ask other questions, such as whether the Martian sand dunes are still active or whether they are simply relics dating back millions or billions of years, when the atmosphere was thicker. As Chojnacki stated:
We wanted to know: is the movement of sand uniform across the planet, or is it strengthened in some areas relative to others? We measured the speed and volume at which the dunes move on Mars.
Sand dunes inside the crater Victoria, near the landing site of the robot Opportunity, seen by MRO on October 3, 2006. Image via NASA / JPL / University of Arizona.
Barchan dunes in the Hellespontus area, seen by the MRO on March 16, 2008. Image via NASA / JPL / University of Arizona.
Spotted sand dunes near the North Martian Pole, seen by the MRO on April 13, 2008. These are places where carbon dioxide ice has sublimated the dunes. Image via NASA / JPL / University of Arizona.
Frosted sand dunes near the North Martian Pole, seen by the MRO on February 19, 2008. Image via NASA / JPL / University of Arizona.
To help understand the causes of sand movement on Mars, researchers used high-resolution images taken by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter (MRO) probe. MRO has been orbiting Mars since 2006, taking thousands of detailed images of the surface all over the planet. For this particular work, the researchers mapped sand volumes, dune migration rates, and heights of 54 dune fields, including 495 individual dunes. Chojnacki said:
This work could not have been done without HiRISE. The data does not come only from images, but comes from our photogrammetry lab that I co-manage with Sarah Sutton. We have a small army of undergraduate students who work part-time and build these digital terrain models that provide a fine-scale topography.
What the researchers found was surprising. Although there are old inactive sand dunes, much remains today. They fill and sweep craters, canyons, faults, fissures, volcanic remains, polar basins and plains surrounding craters. The atmosphere of Mars is perhaps thin, but it still allows to transport grains of sand in a wide variety of landscapes.
Three regions are the most active: Syrtis Major Planum, a dark area larger than Arizona; Hellespontus Montes, a mountain range about two-thirds the length of the Cascades; and Olympia Undae (Northern Polar Erg), a sea of sand surrounding the northern polar ice cap. What makes these areas unique is that they experience conditions that will not necessarily affect sand dunes: abrupt transitions in topography and surface temperatures. According to Chojnacki:
These are not factors that you will find in Earth Geology. On Earth, the factors at play differ from those of Mars. For example, near-surface groundwater or plants growing in the area delay the movement of dune sand.
Close-up view of a sand dune called Namib Dune, which is part of the Bagnold dunes near Mount Sharp in the Gale crater, seen by the Curiosity rover on December 18, 2015. The Namib is about 5 meters (16 feet) from above. Image via NASA / JPL-Caltech / MSSS.
Another view of Curiosity from part of the Bagnold dunes near Mount Sharp in the Gale Crater. Image via NASA / JPL-Caltech / MSSS.
The researchers also found that small basins filled with shiny dust also exhibited higher sand movement speeds, as noted by Chojnacki:
A bright pool reflects the sunlight and warms the air above much faster than the surrounding areas, where the floor is dark, so that the air rises from the basin to the edge of the basin, resulting in the wind and, therefore, the sand.
NASA's Curiosity rover studied a dune field in the crater of Gale, the dunes of Bagnold. Orbiter Mars Odyssey has also recently seen an unusual hexagonal dune field created by Martian winds.
Mars is often considered a desert world, for good reason. Sand dunes flow on the surface, just like in the deserts of the Earth, like the Sahara. In some places, you could swear you were in the American Southwest, with a strangely similar landscape. But Mars is not Earth, and different environmental and geological factors play a key role in the behavior and differences of sand dunes on both worlds.
Conclusion: This new study shows how sand dunes on Mars, although visually and aesthetically similar to their terrestrial counterparts, can differ significantly in the way they are formed and how they migrate to the surface of this planet. desert world and cold.
Source: Boundary Condition Controls in Mars High Sand Flow Regions
Via UANews
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