New Evidence for a Wetter, Warmer Ancient Mars

A 3-D image of a trough in the Nili Fossae region of Mars shows phyllosilcates (in magenta and blue hues) on slopes of mesas and canyon walls, showing water played a role in Mars’ past.

For all the Mars romanticists out there, we (yes, that means me, too) hope and maybe even dream that Mars once harbored water. And not just a little spurt of groundwater every once in awhile; we want the water to have been there in abundance and for enough time to make an impact on the planet and its environment. Now, proof of copious amounts of water in Mars’ past may have been found. Two new papers based on data from the Mars Reconnaissance Orbiter (MRO) found that vast regions of the ancient southern highlands of Mars hosted a water-rich environment, and that water played a sizable role in changing the minerals of a variety of terrains in the Noachian period – about 4.6 billion to 3.8 billion years ago.

John Mustard, a professor of planetary geology at Brown University and deputy principal investigator for the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on MRO investigated the pervasive presence of phyllosilicates, clay-like minerals that preserve a record of water’s interaction with rocks.

Specifically, Mustard and his team from 13 other institutions focused on phyllosilicate deposits in areas like craters, valleys and dunes all over the planet. Among the highlights, he detected the clay-like minerals in fans and deltas within three regions, most notably the Jezero crater. That discovery marks the first time hydrated silicates have been found in sediments “clearly lain by water,” Mustard said.

The team also found phyllosilicate deposits in thousands of places in and around craters, including the pointed peaks located at the center of some of the depressions. This suggests that water was present 4-5 kilometers below the ancient Martian surface, the team wrote, due to the generally accepted principle that crater-causing collisions excavate underground minerals that are then exposed on the crater peaks.

“Water must have been creating minerals at depth to get the signatures we see,” Mustard said.

The clay minerals were formed at low temperatures (100-200°C) – an important clue to understanding the Red Planet’s potential for habitability during the Noachian period.

“What does this mean for habitability? It’s very strong,” Mustard said. “It wasn’t this hot, boiling cauldron. It was a benign, water-rich environment for a long period of time.”

In another paper, graduate student Bethany Ehlmann and colleagues from Brown and other institutions analyzed sediment deposits in two exquisitely preserved deltas in the Jezero crater, which held an ancient lake slightly larger than Lake Tahoe. The deltas suggest a flow from rivers carrying the clay-like minerals from an approximate 15,000-square kilometer watershed during the Noachian period.
Ehlmann said scientists cannot determine whether the river flow was sporadic or sustained, but they do know it was intense and involved a lot of water.

The deltas appear to be excellent candidates for finding stored organic matter, Ehlmann said, because the clays brought in from the watershed and deposited in the lake would have trapped any organisms, leaving in essence a cemetery of microbes.

“If any microorganisms existed on ancient Mars, the watershed would have been a great place to live,” Ehlmann said. “So not only was water active in this region to weather the rocks, but there was enough of it to run through the beds, transport the clays and run into the lake and form the delta,” she said.

Original News Source: Brown University Press Release