So now they want people to think that finding a few organic molecules on Mars is an advance toward finding evidence of past life?
"It's incredibly exciting, because it shows that Mars is an active planet today", says Caltech planetary scientist Bethany Ehlmann, a Mars expert who wasn't involved with the studies. The 96-mile crater, named for Australian astronomer Walter F. Gale, was most likely formed by meteor impact between 3.5 to 3.8 billion years ago. The samples contained methanethiol, thiophene, dimethylsulfide, and 2- and 3-methylthiophenes.
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.
Now, the rover has seemingly made a new discovery which will be revealed this Thursday, according to the space agency.
NASA's Curiosity rover has uncovered organic material in an ancient lakebed and confirmed a seasonal cycle of methane - offering the strongest evidence yet of potential life, past or even present, on the Red Planet.
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As for the methane, Curiosity's Tunable Laser Spectrometer measured the methane levels in its surrounding atmosphere over five years.
All of which will be taken into account when several more Mars lander projects head for the Red Planet in the next two years. Because that's what happens when you go digging around Mars.
Future missions will help. This coincides with the seasons on Mars with the methane levels reaching their peak at the end of summer in the Northern hemisphere.
"This is all possible because of Curiosity's longevity. The long duration has allowed us to see the patterns in this seasonal 'breathing, '" Webster added. Mars2020 will shed light on the organic molecules-and prepare a sample that some future mission could bring back to Earth. "Organic" carbon can mean biologically derived, but it can also have nonbiological sources. But it is the preservation of the material that is important - if there is this much organic matter preserved close to the surface, then there should be even better protected material at greater depths.
These might explain the increase in molecules, but they do still leave its rapid vanishing act wanting of an explanation.
There is a seasonal variation to the methane that repeats, which means the methane is being released from the Martian surface or from reservoirs beneath the surface. Here it is retained by the soil until the temperature increases sufficiently to release the gas.
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A crystalline water structure called a clathrate provides a flawless explanation. On Earth, 1,800 out of every billion molecules in the atmosphere is methane, and 95 percent of it comes for biological sources: Burning fossil fuels, decomposing debris, burping cows.
The source is still unclear, but it may be stored in the cold Martian subsurface in water-based crystals called clathrates, researchers said. Some of our planet's earliest organisms may have been methanogens - microbes that eat organic molecules and exhale methane gas.
So, just where did the methane come from in the first place? "It's on the table with all the other ones", Dr. Eigenbrode said.
"The question of whether life might have originated or existed on Mars is a lot more opportune now that we know that organic molecules were present on its surface at that time", Kate said.
"Are there signs of life on Mars?" asked Michael Meyer, lead scientist for the Mars Exploration Program at NASA Headquarters. "The first one would be life, which we don't know about".
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