Zhurong spotted telltale patterns in Martian dunes.
The crescent shape of the dunes has been eroded over hundreds of thousand years, with long dark ridges, called transverse aeolian ridges , forming on top of the dune fields, but apparently at a different angle than that of the wind-blown dunes. TARs have been observed all across
at lower mid-latitudes, but global atmospheric circulation models that describe the direction of the winds on the Red Planet have been unable to explain how the features could have formed — until now.How Mars' winds changed as the ice age came to an end, forming long ridges at a different angle to the dunes.
Zhurong's investigation of the dunes found that their crescent-shaped bodies are made of brighter material underneath the darker material that forms the TARs. From orbit, Tianwen-1 observed 2,262 bright dunes across Mars, and based on the number of craters that have impacted on top of the dunes, the research team estimates that they formed between 2.1 million and 400,000 years ago. That means the dark TARs must have formed on top of them within the past 400,000 years.
These dates coincide with the start and end of Mars' last major ice age. For the TARs to have formed at a different angle to the dunes implies that the wind direction in the lower mid-latitudes must have changed with the end of the ice age.
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