Potential building blocks of life found on Mars
New Mars discoveries are advancing the case for possible life on the red planet, past or even present.
Scientists reported yesterday that Nasa's Curiosity rover has found potential building blocks of life in an ancient Martian lakebed. Hints have been found before, but this is the best evidence yet.
The organic molecules preserved in 3.5 billion-year-old bedrock in Gale Crater - believed to have once contained a shallow lake - suggest conditions back then may have been conducive to life.
That leaves open the possibility that micro-organisms once populated our planetary neighbour and might still exist there.
"The chances of being able to find signs of ancient life with future missions, if life ever was present, just went up," said Curiosity project scientist Ashwin Vasavada of Nasa's Jet Propulsion Laboratory (JPL) in Pasadena, California.
Curiosity has also confirmed sharp seasonal increases of methane in the Martian atmosphere.
Researchers said they cannot rule out a biological source. Most of Earth's atmospheric methane comes from animal and plant life, and the environment itself.
The two studies appear in the journal Science.
In a companion article, an outside expert describes the findings as "breakthroughs in astrobiology".
Kirsten Siebach, a Rice University geologist who was also not involved in the studies, is equally excited.
She said the discoveries break down some of the strongest arguments put forward by life-on-Mars sceptics, herself included.
"The big takeaway is that we can find evidence.
"We can find organic matter preserved in mudstones that are more than three billion years old," Ms Siebach said.
"And we see releases of gas today that could be related to life in the subsurface or at the very least are probably related to warm water or environments where Earth life would be happy living."
The methane observations provide "one of the most compelling" cases for present-day life, she said.
Scientists agree more powerful spacecraft - and, ideally, rocks returned to Earth from Mars - are needed to prove whether tiny organisms like bacteria ever existed on the red planet.
Curiosity's methane measurements occurred over four-and-a-half Earth years, covering parts of three Martian years.
Seasonal peaks were detected in late summer in the northern hemisphere and late winter in the southern hemisphere.
JPL's Christopher Webster, lead author on the study, said it is the first time Martian methane has shown a repeated pattern.
The magnitude of these seasonal peaks - by a factor of three - was far more than scientists expected.
"We were just blown away," he said. "It's tripling... that's a huge, huge difference."
As with methane, there could well be non-biological explanations for the presence of carbon-containing molecules on Mars, such as geologic processes or impacts by asteroids, comet, meteors and interplanetary dust.