Supersalty Water Could’ve Erased Some Evidence of Life on Mars

Rocks on Mars protect a report of the planet’s historic previous, however a shocking discovery made by NASA’s Curiosity rover exhibits some patches of Martian rock have had their histories fully erased.

The main goal of NASA’s Curiosity mission is to judge the prior potential for habitability on Mars, whereas the newly arrived Perseverance mission goals to search out precise remnants or indicators of prior life. To that finish, Curiosity has been investigating sedimentary rocks in Gale crater, that are full of clay minerals. Clay is a crucial marker of habitability, because it suggests the previous presence of liquid water—a key ingredient for all times.

Using its Chemistry and Mineralogy instrument, also called CheMin, the six-wheeled rover has been analyzing drill samples of sedimentary layers alongside the decrease reaches of Mount Sharp. In 2019, a fortuitous pathway from Vera Rubin ridge to Glen Torridon made it attainable for Curiosity to look at a mudstone layer that shaped in a Martian lake some 3.5 billion years in the past.

The rover took samples from two areas positioned lower than 1,310 ft (400 meters) aside. Research printed as we speak in Science describes sudden variations in these two areas, as one patch featured solely half of the anticipated quantity of clay minerals. Instead, these historic mudstones have been full of iron oxides, which, apparently sufficient, is the stuff that offers Mars its iconic pink hue.

The mudstone from each patches dates again to the identical time and place, in order that they ought to include related quantities of clay minerals. This shocking commentary required the researchers, led by Tom Bristow from NASA’s Ames Research Center, to conjure a proof for the lacking clay. Indeed, historic rocks are identified for being repositories of historical past, however as the brand new analysis exhibits, pure geological processes can undo this report.

To clarify what occurred, the group posited a situation by which water leaked down into the clay from a sulfate deposit positioned immediately above. The supersalty brines seeped by way of grains of sand on the backside of the previous lake and, by doing so, ceaselessly modified the mineral-rich layers beneath.

“We used to think that once these layers of clay minerals formed at the bottom of the lake in Gale Crater, they stayed that way, preserving the moment in time they formed for billions of years,” Bristow defined in a NASA statement. “But later brines broke down these clay minerals in some places—essentially resetting the rock record.”

In an e-mail, Bristow stated the brand new analysis provides to the steadily rising image of historic Martian habitability.

“It backs up previous evidence that showed fluids continued to move through Gale crater rocks long after they were deposited,” he defined. “It also shows that there were geochemical gradients—some parts of the rocks were affected more than others and fluid chemistry changed,” stated Bristow, including that organic organisms “can use geochemical gradients to capture energy.”

This course of wasn’t uniform throughout the underside of the previous lake, because it occurred after the lake misplaced its liquid water, in response to the analysis. Groundwater in Gale crater continued to stream—and in addition transport and dissolve chemical substances—beneath the floor. As a consequence, some pockets of subsurface mudstone have been uncovered to totally different situations. Those pockets uncovered to the salty water underwent a course of referred to as “diagenesis,” by which the altering mineralogy worn out the geological—and presumably organic—report.

Interestingly, if not mockingly, diagenesis may create environments pleasant to microbes even because it erased potential proof of life, in response to John Grotzinger, a co-author of the examine and a professor of geology at Caltech.

“These are excellent places to look for evidence of ancient life and gauge habitability,” Grotzinger stated within the assertion. “Even though diagenesis may erase the signs of life in the original lake, it creates the chemical gradients necessary to support subsurface life, so we are really excited to have discovered this.”

I like this paper for a number of causes. First, it improves our understanding of the geological processes on the Red Planet and its unanticipated complexities. Second, it’s a reminder that Curiosity remains to be doing necessary work on Mars, even 9 years after it first began rolling and as Perseverance begins to steal the limelight.

This examine can now inform the Perseverance group as they consider targets for investigation and select rock samples that might finally be dropped at Earth for nearer evaluation. Excitingly, the 2 rovers at the moment are working as a group (though they’re 2,300 miles aside), and, in so doing, they will affect one another’s work.

More: NASA’s ‘other’ Mars rover sends again a selfie to remind us it nonetheless exists.