Almost six years into its survey of a site called Gale Crater on Mars, NASA's Curiosity rover has delivered what may be the biggest discovery yet in its quest for signs of habitability and life: Organic molecules are abundant in Red Planet rocks, and the simplest organic molecule, methane, seasonally blows through the thin Martian air. On the top of scientists' wish list was evidence of organic matter, which emerged in 2013. The 2020 rover will include an advanced spectrometer to scan for organic molecules.
NASA's Curiosity Mars Rover drilled this hole to collect sample material from a rock target called "Buckskin" on July 30, 2015, during the 1060th Martian day, or sol, of the rover's work on Mars.
And that did the trick.
"We have just satisfied a mission objective for Curiosity", says Jennifer Eigenbrode, study lead author and a member of the Mars Science Laboratory mission team.
Is this the discovery of Martians? While commonly associated with life, organic molecules also can be created by non-biological processes and are not necessarily indicators of life. In this case, the scientists couldn't tell how these organics were formed.
As promised, NASA has announced new milestone Mars discoveries, namely the presence of organic molecules and seasonal changes in atmospheric methane.
"That is a good place for life to have lived if it ever existed on Mars", she said. It's possible, ten Kate said, that this could happen on Mars.
Curiosity has detected organics embedded in the sediments of the "Pahrump Hills" area of Gale Crater.
A view of Ophir Chasma on the northern portion of the vast Mars canyon system, Vallles Marineris, taken by NASA's Mars Reconnaissance Orbiter. And NASA didn't launch another mission to Mars for over a decade.
The US space agency promised to unveil its latest findings from the red planet. "We didn't want to fund an incredibly expensive mission and come up short again".
"Viking was this sort of shot in the dark", says David Grinspoon, an astrobiologist with the Planetary Science Institute.
"We don't know, but these results tell us we are on the right track"'.
But the deposits were much smaller than they had anticipated.
Clearly, there are more questions about Mars that need answering. The organic molecules and volatiles, comparable to samples of sedimentary rock rich in organics on Earth, included thiopene, methylthiophenes methanethiol and dimethylsulfide. So the Martian traces of organic matter do hint that the basic conditions for life to form were present on Mars at around the same time they existed on Earth. Finding organics is critical. Organic entails "containing carbon", as this NASA video says, but organic molecules can have biological or non-biological origins. The Viking Project was the first USA mission to safely land spacecraft on the Martian surface, as well as send back images. But they could also be the result of abiotic chemical reactions on the surface of the planet. So they looked elsewhere. "And we see releases of gas today that could be related to life in the subsurface or at the very least are probably related to warm water or environments where Earth life would be happy living".
The rover has been seeing seasonal changes in the amount of methane in the Martian atmosphere.
Meanwhile, the scientists hope that the newly discovered methane cycle could lead them to understand where the gas originates and if it is a sign of life. So like the organic molecules, it's not an unambiguous biosignature.
The Curiosity rover has not been able to find the source of the organic molecules in its findings, according to the report. Combined with high-energy ultraviolet light and cosmic rays streaming in from space, perchlorates would destroy any organic material on the surface, leaving little to be seen by carbon-seeking landers and rovers.
NASA will use both these discoveries to inform the design of its upcoming Mars 2020 rover.
"Curiosity has not determined the source of the organic molecules", Eigenbrode said in the release. Even more compelling was the fact that these compounds seemed to have broken off even bigger, more complex "macromolecules" - substances found on Earth in coal, black shale and other ancient organic remains. That next step is to try to figure out if life is involved.
Water-rock chemistry might have generated the methane, but scientists can not rule out the possibility of biological origins. "Whether there was in the past or not is certainly an open question".