Mars could not have had liquid water lengthy sufficient for all times to kind

Enlarge (credit score: NASA/JPL-Caltech/College of Arizona)

Mars has a historical past of liquid water on its floor, together with lakes just like the one which used to occupy Jezero Crater, which have lengthy since dried up. Historic water that carried particles—and melted water ice that presently does the identical—have been additionally considered the one factor driving the formation of gullies unfold all through the Martian panorama. That view could now change because of new outcomes that counsel dry ice may also form the panorama.

It’s elegant

Beforehand, scientists have been satisfied that solely liquid water formed gullies on Mars as a result of that’s what occurs on Earth. What was not taken into consideration was sublimation, or the direct transition of a substance from a stable to a gaseous state. Sublimation is how CO₂ ice disappears (generally water ice experiences this, too).

Frozen carbon dioxide is in all places on Mars, together with in its gullies. When CO₂ ice sublimates on certainly one of these gullies, the ensuing gasoline can push particles additional down the slope and proceed to form it.