Credit & Copyright: HiRISE,
MRO,
LPL (U. Arizona),
NASA;
Processing:
Weodek Geaeewski;
Text: Alex R. Howe (NASA/USRA, Reader's History of SciFi Podcast)
Explanation:
Why are these sand dunes on
Mars striped?
No one is sure.
The featured image shows striped dunes in
Kunowsky Crater on Mars, photographed recently with the
Mars Reconnaissance OrbiterBs HiRISE Camera.
Many Martian dunes are known to be covered unevenly with carbon dioxide
(dry ice) frost,
creating patterns of light and dark areas.
Carbon dioxide doesnBt melt, but
sublimates, turning directly into a gas.
Carbon dioxide is also a
greenhouse material even
as a solid,
so it can trap heat under the ice and
sublimate from the bottom up, causing
geyser-like eruptions.
During Martian spring, these eruptions can cause a pattern of dark
defrosting spots, where the
darker sand is exposed.
The featured image, though, was taken during Martian autumn,
when the weather is getting colder B making these stripes particularly puzzling.
One hypothesis is that they are caused by cracks in the ice that form from weaker
eruptions or
thermal stress as part
of the day-night cycle, but research continues.
Watching these dunes and others through more
Martian seasons
may give us more clues to solve this mystery.
Text: Alex R. Howe (NASA/USRA, Reader's History of SciFi Podcast)
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