While not direct evidence of life, the compounds drilled from Mars' Gale Crater are the most diverse array ever taken from the surface of the planet since the robotic vehicle landed in 2012, experts say.
The new evidence comes from a pair of rocks.
NASA is to announce new findings from Curiosity in a conference streamed live worldwide on Thursday. Curiosity sampled mudstone in the top 5 centimeters from the Mojave and Confidence Hills localities within Gale Crater.
They don't exactly roll off the tongue, but researchers believe that these are fragments of larger molecules that were present on Mars billions of years ago.
This time, UFO fans are particularly excited because one of the scientists, Jennifer Eigenbrode, is described as an "astrobiologist".
Potential contaminants were analyzed and accounted for, so the results are the most conclusive yet. Unfortunately, the new findings do not allow us to say anything about the presence or absence of life on Mars now or in the past. "Organic molecules are usually composed of carbon atoms in rings or long chains, to which are attached other atoms of such elements as hydrogen, oxygen, and nitrogen". "We don't know, but these results tell us we are on the right track".
Data from the plucky rover Curiosity and the Trace Gas Orbiter high above the planet have spotted it in puffs, suggesting a dynamic process is churning it out parts per billion.
And then there's the most intriguing possibility. Much as a detective figures out whodunnit by filling in all the details of a crime first, astrobiologists set about piecing together a picture of the Martian environment to figure out if the planet could even support life, now or in the past.
But the boffins are far from certain the the organic molecules or methane that Curiosity turned up have anything to do with life.
She isn't ruling out that possibility, however. "A rigorous approach based on available evidence starts with the scientifically responsible default explanation that Mars is and always has been lifeless", Fries says. "Whether there was in the past or not is certainly an open question". Hints have been found before, but this is the best evidence yet.
The scientists were surprised to find organic compounds, especially in the amounts detected, considering the harsh conditions, including bombardment of solar radiation on the Martian surface. There may be more material buried deeper. And Curiosity dug a little deeper beneath the surface, which is blasted with radiation, to see what stories the soil had to tell. The seasonal variation provides an important clue for determining the origin of martian methane.
Here on Earth, 95 percent of all methane molecules are the product of living chemistry.
"We were kind of shocked to see that with the seasons, the signal changes by a factor of three, which is a huge change and completely unexpected", says Chris Webster, a rover scientist at NASA's Jet Propulsion Laboratory. They therefore suggest that methane could be trapped at depth, gradually seeping to the surface. "So it holds it in the winter time and releases it in the summertime as temperatures get warmer".
The results also indicate organic carbon concentrations on the order of 10 parts per million or more. Answers to life's biggest questions? Mission scientists announced today in a paper published in the journal Science that Curiosity discovered a whole catalogue of preserved organic matter in the first rock layers that the rover checked there.