Snow may have fallen on Mars 400,000 years ago

Mars seems to have had liquid water on its floor as lately as 400,000 years in the past, probably beginning as snow that melted and helped flip sand dunes into stable, cracked crusts, based on photos taken by China’s Zhurong rover.

Numerous proof factors in direction of Mars having had huge deposits of liquid water sooner or later in its historic previous, however how lengthy this water endured for or how a lot made it to the planet’s current previous is unclear.

Now, Xiaoguang Qin on the Chinese language Academy of Sciences in Beijing and his colleagues have discovered cracks, crusts and clumps of particles on prime of sand dunes within the Martian plain of Utopia Planitia that may solely be defined by liquid water from between 400,000 and 1.4 million years in the past.

“Sand dunes are a extra fashionable landform,” says Qin. “These crusts on the dunes’ surfaces have solidified the sand dunes and stopped them shifting.”

The presence of sure salts within the sand led the workforce to imagine the water initially fell onto the sand dunes within the type of snow or frost, which later melted and blended with the sand to kind hydrated minerals. These minerals then clumped collectively and, as soon as the water evaporated, have been cemented in place and shaped the cracked crust seen by the rover’s digital camera.

The mechanism that Qin and his workforce suggest for the cracks having shaped by a water-based cement is convincing, says Matt Balme on the Open College within the UK, however there may be nonetheless a chance that it might have shaped by one other Martian geological mechanism that we aren’t conscious of on Earth, he says.

Given what number of sand dunes have been seen in different Mars missions, it is perhaps value revisiting these photos to see if comparable options will be discovered, says Balme.