The Curiosity science team has also announced that it has found what are referred to as "organic molecules" in 3-billion-year-old sedimentary rocks near the surface.
This engineering marvel, NASA's Mars rover Curiosity, has revolutionized our understanding of the red planet. In another paper published simultaneously in the journalScience, they describe background levels of methane, also an organic, in Mars's atmosphere that varies seasonally.
Water-rock chemistry might have generated the methane, but scientists can not rule out the possibility of biological origins.
Mars's Gale Crater, where Curiosity has been trolling around for the past six years, is a particularly interesting place to look for those molecules.
At this point, there's simply no way of knowing whether the organic molecules and the methane findings point to potential life on Mars.
The surface of Mars may be inhospitable today, but there is strong evidence that the Martian climate once accommodated liquid water - which, as most of you will know, is one of the key components to life - to pool at the surface. The changes were observed over three Martian years, which are equivalent to almost half a dozen Earth years.
By themselves, the new results aren't evidence for ancient life on Mars; non-living processes could have yielded identical molecules.
"And maybe we can find something better preserved than that, that has signatures of life in it", added Ms Eigenbrode, an astrobiologist at NASA Goddard Spaceflight Center.
"I don't believe there's life on Mars at the present", Freeman says, because Mars is very dry, very cold and lacks much of an atmosphere. One group found carbon-containing organic matter in 3.5-billion-year-old rock.
Researchers say they will require further samples that have not been irradiated in order to get a clearer picture of the origin of the organic matter. This mudstone gradually formed billions of years ago from silt that accumulated at the bottom of the ancient lake.
The Curiosity rover has lasted three times as long as it was meant to and is still going, which helped with the study of seasonal methane cycles.
Over five years, Curiosity has used its Tunable Laser Spectrometer to measure methane in the atmosphere at the Gale crater.
Spikes and plumes of methane in Mars's thin atmosphere have been detected by several missions over more than two decades, but they have been frustrating to study, said Christopher Webster, who led the methane study.
This seasonal pattern seems to imply that temperature changes might be triggering the seasonal release, the scientists said, suggesting that the methane might be stored in water-based crystals called clathrates. Seasonal peaks were detected in late summer in the northern hemisphere and late winter in the southern hemisphere. "It is not telling us that life was there, but it is saying that everything organisms really needed to live in that kind of environment, all of that was there", explained Eigenbrode.
"Are there signs of life on Mars?" said Michael Meyer, lead scientist for NASA's Mars Exploration Program, at NASA Headquarters.
"With this new data, we again can not rule out microbial activity as a potential source", Webster said.
"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.
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As his backhand return on his fourth match point landed beyond the outstretched arm of Djokovic, the tears flowed. Serbia's Novak Djokovic with Spain's Fernando Verdasco after winning their fourth round match.
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National Basketball Association officials said via Twitter , "We missed this one - it should have been a foul". And while Game 3 tips off in Cleveland tomorrow night, James still gets questions about his Game 1 reactions.
He emphasized that this is the development under leadership of Prime Minister Narendra Modi and Union Minister Arun Jaitley. The role of fiscal policy was also clear in government consumption data that saw a growth of 16.8 percent year-on-year.
Play continued though, with the set following a similar pattern to the first, as Nadal broke back before dropping his serve to 15. The match had already been stopped for an hour on Wednesday, with Nadal trailing 6-4 2-1, before play resumed at 17:28 BST.
England v Costa Rica Live on ITV
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