Landforms Suggest Liquid Water was on Mars Relatively Recently

A geographic analysis of the southern hemisphere on Mars suggests that the landforms there were formed by running liquid water in geologically recent times.

Writing in the solar system studies journal Icarus, scientists report that a large crater in Mars's south is home to well-preserved gullies and debris flow deposits that appear to have been formed by liquid water.

Debris flows occur when sediment becomes so saturated with water it gets too heavy to remain in place, sinking downward as a single unit along a slope.

When a debris flow on Earth comes to a stop it displays characteristic surface features including lobate deposits and paired levees along flow channels, the scientists said, noting that these same features have been observed within the Martian crater.

The topography of debris flow remnants on the Norwegian islands of Svalbard were compared to what the scientists observed on Mars, and they appear to be a geomorphological match.

"Our fieldwork on Svalbard confirmed our interpretation of the Martian deposits," said lead study author Andreas Johnsson of Sweden's University of Gothenburg. "What surprised us was that the crater in which these debris flows have formed is so young."

Johnsson and his collaborators report the age of the Martian crater to be about 200,000 years old, which is about 200,000 years after the end of Mars's last ice age.

That the crater formed so long after the last Martian ice age suggests that water must have been on the planet relatively recently, in geological terms.

"Gullies are common on Mars, but the ones which have been studied previously are older, and the sediments where they have formed are associated with the most recent ice age," Johnsson said in a statement. "Our study crater on Mars is far too young to have been influenced by the conditions that were prevalent then. This suggests that the meltwater-related processes that formed these deposits have been exceptionally effective also in more recent times."

Possible sources that the scientists have suggested for the water include melting snow packs from when conditions on Mars were more favorable for snow, or that the planet's orbital axis was more tilted in the past than it is today.