"If there are no organics, we can pretty much forget about there being life or ever having been life on Mars", says Dr. Weintraub. When they did experiments in their laboratory on Earth to bake samples containing those three types of organic carbon, the readings were all consistent with what was detected on Mars. Organic matter can be one of several things: a record detailing ancient life, a food source for life or something that exists in the place of life.
In a second, potentially more significant finding announced Thursday, scientists reported detection of a seasonal variation in methane levels in the martian atmosphere.
The rock fragments were heated to more than 900 degrees Fahrenheit, and the rover's instruments looked at the molecules that wafted away at the high temperatures.
'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.
Finding methane in the atmosphere and ancient carbon preserved on the surface gives scientists confidence that NASA'sMars 2020 rover and ESA's (European Space Agency's) ExoMars rover will find even more organics, both on the surface and in the shallow subsurface.
At this point, we simply don't know whether the origin is biological or geological.
The studies on methane and on organic molecules were published Thursday in the journalScience.
NASA now operates three orbiters and two surface rovers at Mars with a new lander - InSight - on the way. While commonly associated with life, organic molecules also can be created by non-biological processes and are not necessarily indicators of life.
These chemicals might not mean a great deal to most of us, but to areologists (that's Martian geologists) it's an indication that the organic chemistry in Martian mudstone is extremely similar to our own.
One thing is for sure, though - whatever we can figure out about the chemistry of Mars, it's nearly certainly going to add precious details to our understanding of life in the cosmos.
What they claimed they had discovered was a fossilised micro-organism in a Martian meteorite, which they argued was evidence that there has once been life on the Red Planet. That leaves open the possibility that microorganisms once populated the red planet - and still might.
"There's three possible sources for the organic material", said astrobiologist Jennifer Eigenbrode of NASA's Goddard Space Flight Center in Maryland.
Curiosity has detected organics embedded in the sediments of the "Pahrump Hills" area of Gale Crater.
Over the years, scientists have amassed a number of clues that can help answer the question of Mars' habitability, including evidence of liquid water.
The Gale Crater was probably habitable 3.5 billion years ago, based on what Curiosity has shown us.
"We have no proof that the methane is formed biologically, but we can not rule it out, even with this new data set", Webster said.
NASA also has another rover in the works with its Mars 2020 mission, which plans to drill cores and set them aside for a possible future pickup and return to Earth.