Curiosity Rover Makes Intriguing New Discoveries About Martian Organics and Methane

“Self-portrait” of the Curiosity rover on Vera Rubin Ridge. Photo Credit: NASA/JPL-Caltech/MSSS

Is there or has there ever been life on Mars? We still don’t know the answer for sure, but two new findings announced this morning by NASA during a live discussion provide more tantalizing clues. The new results come from the Curiosity rover in Gale crater, and build on previous data collected by the rover. They concern two key findings – organics and methane, both of which could have significant implications for the possibility of life on Mars.

“With these new findings, Mars is telling us to stay the course and keep searching for evidence of life,” said Thomas Zurbuchen, associate administrator for the Science Mission Directorate at NASA Headquarters, in Washington. “I’m confident that our ongoing and planned missions will unlock even more breathtaking discoveries on the Red Planet.”

The findings have been published in the June 8 edition of the journal Science.

First, the organics. Organics, which are the building blocks of life, have been found before, but the new results show a greater variety than previously seen and some of those are “tough” molecules in the first five centimeters of rock which haven’t been broken down by the harsh ultraviolet radiation or other chemicals. That is a good sign that even more complex organic molecules are still waiting to be found deeper inside rocks and under the surface of the planet.

Curiosity has discovered the remains of complex organic molecules in ancient mudstone sedimentary rocks on Mars. Image Credit: NASA/GSFC

Diagram depicting the seasonal variation of methane in the Martian atmosphere as detected by Curiosity. Image Credit: NASA/JPL-Caltech

Mudstone lakebed sedimentary deposits seen by the Curiosity rover in Gale crater. This is where a variety of ancient organics have been discovered so far. Photo Credit: NASA/JPL-Caltech

The organics have been found in sedimentary mudstone rocks which used to be at the bottom of an ancient lakebed in Gale crater. The rock samples were analyzed by the SAM instrument, which uses an oven to heat the samples (in excess of 900 degrees Fahrenheit (500 degrees Celsius) to release organic molecules from the powdered rock. Some of the molecule fragments contain sulfur, which helps to preserve them.

Curiosity found significant concentrations of organic carbon, 10 parts per million or more, similar to that found in Martian meteorites and about 100 times greater than prior detections of organic carbon on Mars’ surface. The variety of organic molecules found include thiophenes, benzene, toluene, and small carbon chains, such as propane or butene.

Organics are of course necessary for life as we know it, but it is not known yet if these molecules came from ancient life or were formed by non-biological processes.

“Curiosity has not determined the source of the organic molecules,” said Jen Eigenbrode of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, lead author of one of the two new Science papers. “Whether it holds a record of ancient life, was food for life, or has existed in the absence of life, organic matter in Martian materials holds chemical clues to planetary conditions and processes.”

Curiosity’s newest drill hole, after testing a new drilling technique in a rock target called Duluth. This is the first successful drilling since December 2016 after mechanical problems with the drill. Photo Credit: NASA/JPL-Caltech/MSSS

The methane is another exciting discovery, since it could indicate active biology on Mars now, likely beneath the surface. The new paper explains that Curiosity scientists have now pinned down the seasonal variations of the organic gas in the atmosphere, detected by Curiosity’s Sample Analysis at Mars (SAM) instrument suite. Curiosity has tracked the methane for nearly three Mars years (almost six Earth years).

The methane peaks during warmer summer months and then drops back down during the winter. This could be explained by either water-rock interactions, perhaps involving clathrates, or even biology, below the surface.

“This is the first time we’ve seen something repeatable in the methane story, so it offers us a handle in understanding it,” said Chris Webster of NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, lead author of the second paper. “This is all possible because of Curiosity’s longevity. The long duration has allowed us to see the patterns in this seasonal ‘breathing.'”

As noted in the live discussion, the peak methane detections, although still small compared to Earth, were about three times greater than expected, a surprising find. This constrains the possible sources, and makes some other possibilities, such as methane molecules coming from meteorites, much less likely, according to the scientists involved. The source now seems to be underground, either geological or biological. On Earth, the vast majority of methane comes from bacteria and other life forms. Even if the source is just geology, it would mean there is still warm water beneath Mars’ cold surface, which itself would be a habitable environment.

Gale crater as seen from orbit. The crater used to hold a lake or series of lakes a few billion years ago, and, maybe, some form of life. Image Credit: NASA/JPL-Caltech/ESA/DLR/FU Berlin/MSSS

It is difficult for Curiosity to determine the specific origin of the methane due to the low amounts seen so far, but the European Trace Gas Orbiter spacecraft is also currently studying it, and is designed to analyze it in more detail.

“With these new findings, Mars is telling us to stay the course and keep searching for evidence of life,” said Thomas Zurbuchen, associate administrator for the Science Mission Directorate at NASA Headquarters, in Washington. “I’m confident that our ongoing and planned missions will unlock even more breathtaking discoveries on the Red Planet.”

As noted by Michael Meyer, lead scientist for NASA’s Mars Exploration Program, at NASA Headquarters:

“Are there signs of life on Mars? We don’t know, but these results tell us we are on the right track.”

NASA’s upcoming 2020 rover will continue the study of Martian organics, but will specifically look for evidence of ancient life itself.

More information about Curiosity is available on the mission website.

 

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