Rocks on Mars protect a file of the planet’s historical previous, however a stunning discovery made by NASA’s Curiosity rover reveals some patches of Martian rock have had their histories utterly erased.
The first objective 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 stuffed with clay minerals. Clay is a vital marker of habitability, because it suggests the previous presence of liquid water—a key ingredient for all times.
Utilizing 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 potential for Curiosity to look at a mudstone layer that fashioned in a Martian lake some 3.5 billion years in the past.
The rover took samples from two areas situated lower than 1,310 ft (400 meters) aside. Analysis printed at the moment in Science describes surprising variations in these two areas, as one patch featured solely half of the anticipated quantity of clay minerals. As an alternative, these historical mudstones had been filled with iron oxides, which, curiously sufficient, is the stuff that provides Mars its iconic crimson hue.
The mudstone from each patches dates again to the identical time and place, so that they ought to comprise related quantities of clay minerals. This stunning commentary required the researchers, led by Tom Bristow from NASA’s Ames Analysis Heart, to conjure a proof for the lacking clay. Certainly, historical rocks are recognized for being repositories of historical past, however as the brand new analysis reveals, pure geological processes can undo this file.
To elucidate what occurred, the workforce posited a situation by which water leaked down into the clay from a sulfate deposit situated straight above. The supersalty brines seeped via grains of sand on the backside of the previous lake and, by doing so, without end modified the mineral-rich layers under.
“We used to assume that when these layers of clay minerals fashioned on the backside of the lake in Gale Crater, they stayed that method, preserving the second in time they fashioned for billions of years,” Bristow defined in a NASA statement. “However later brines broke down these clay minerals in some locations—primarily resetting the rock file.”
In an electronic mail, Bristow mentioned the brand new analysis provides to the steadily rising image of historical Martian habitability.
“It backs up earlier proof that confirmed fluids continued to maneuver via Gale crater rocks lengthy after they had been deposited,” he defined. “It additionally reveals that there have been geochemical gradients—some elements of the rocks had been affected greater than others and fluid chemistry modified,” mentioned Bristow, including that organic organisms “can use geochemical gradients to seize power.”
This course of wasn’t uniform throughout the underside of the previous lake, because it occurred after the lake misplaced its liquid water, based on the analysis. Groundwater in Gale crater continued to circulation—and likewise transport and dissolve chemical compounds—beneath the floor. As a consequence, some pockets of subsurface mudstone had been uncovered to completely different situations. These pockets uncovered to the salty water underwent a course of known as “diagenesis,” by which the altering mineralogy worn out the geological—and presumably organic—file.
Curiously, if not mockingly, diagenesis may create environments pleasant to microbes even because it erased potential proof of life, based on John Grotzinger, a co-author of the research and a professor of geology at Caltech.
“These are wonderful locations to search for proof of historical life and gauge habitability,” Grotzinger mentioned within the assertion. “Regardless that diagenesis could erase the indicators of life within the authentic lake, it creates the chemical gradients essential to help subsurface life, so we’re actually excited to have found this.”
I like this paper for a number of causes. First, it improves our understanding of the geological processes on the Pink Planet and its unanticipated complexities. Second, it’s a reminder that Curiosity continues to be doing essential work on Mars, even 9 years after it first began rolling and as Perseverance begins to steal the limelight.
This research can now inform the Perseverance workforce as they consider targets for investigation and select rock samples that would ultimately be delivered to Earth for nearer evaluation. Excitingly, the 2 rovers at the moment are working as a workforce (although they’re 2,300 miles aside), and, in so doing, they will affect one another’s work.
Extra: NASA’s ‘different’ Mars rover sends again a selfie to remind us it nonetheless exists.