NASA's Curiosity rover is finding a growing number of evidence that suggests the possibility that Mars supported life. Earlier this month, the U.S. space agency revealed that data gathered by the car-sized robotic probe show that the Red Planet's Gale Crater was once a lake that thrived for a length of time experts believed would have been sufficient to start and support life.
Now, the Curiosity team again unveiled another of the probe's findings that shows Mars' capability to host microbial life. On Tuesday, NASA said that the rover has detected a spike in methane levels on the Red Planet.
Over a period of two months from late 2013 to early 2014, Curiosity's measurements showed that the average level of methane in the Martian atmosphere increased ten times at seven parts per billion before the readings returned to only one-tenth of that level.
Finding methane on planet Mars is particularly significant because on Earth, over 90 percent of methane is produced by biological processes, which means that a chunk of atmospheric methane can be attributed to living organisms.
While a significant amount of methane on the Red Planet is not a guaranteed indication of life on Mars as geological processes also produce gas, many scientists think that finding methane on extraterrestrial worlds would be a good starting point in searching for life beyond Earth. For now, experts are not yet certain on what caused the spike in Mars' methane levels.
"This temporary increase in methane -- sharply up and then back down -- tells us there must be some relatively localized source," said Sushil Atreya of the Curiosity rover science team. "There are many possible sources, biological or non-biological, such as interaction of water and rock."
Using its Sample Analysis at Mars (SAM) instrument, Curiosity also detected different organic molecules when it analyzed samples drilled from a rock known as Cumberland providing the first definitive proof of organics on the surface of the Red Planet.
On Earth, organic molecules that contain carbon and hydrogen are the building blocks of life but these can exist without the presence of life but while these organic compounds do not provide evidence that Mars has harbored living microbes, these show that ancient Mars had conditions favorable for life.
"We think life began on Earth around 3.8 billion years ago, and our result shows that places on Mars had the same conditions at that time - liquid water, a warm environment, and organic matter," said Caroline Freissinet, from NASA's Goddard Space Flight Center. "So if life emerged on Earth in these conditions, why not on Mars as well?"