NASA announced Thursday that its nuclear-powered Curiosity rover has discovered organic matter embedded in the sedimentary rocks of the three-billion-year-old Gale Crater on Mars, giving newfound impetus to the possibility that extraterrestrial life existed on the planet at some point in time.
The organic molecules found in the ancient bedrock suggest that conditions back then may have been ideal to support some form of life, with a good chance that microorganisms once thrived on the red planet.
Despite numerous tests, researchers are unable to give a definitive reason for the formation of the organic matter found, leaving open three main possibilities.
- The material had its origin elsewhere in the universe and was carried to Mars in a comet, or other such celestial bodies crashing into the Martian surface.
- They are the remnants of ancient organisms that lived on the planet billions of years ago.
- They are the by-products of chemical reactions that the rocks underwent over time.
However, regardless of the origin of the organics, their presence itself means that they were a good source of food for any microbes that may have existed back then.
“We know that on Earth microorganisms eat all sorts of organics. It’s a valuable food source for them,” said Jennifer Eigenbrode – a NASA biogeochemist and geologist with expertise in organic and isotope biogeochemistry and interests in astrobiology.
“While we don’t know the source of the material, the amazing consistency of the results makes me think we have a slam-dunk signal for organics on Mars,” she said.
“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,” added Eigenbrode.
The car-sized Curiosity rover – a crucial cog in the wheel of NASA’s Mars Science Laboratory (MSL) mission – landed on the planet in November 2011 and has since navigated 12 miles, investigating the geology – specifically the Gale Crater, which it was designed to explore – as well as the Martian atmosphere and climate.
Curiosity discovered a whole lot of organic molecules in the chunks of Gale’s bedrock it kept drilling up for heat tests in the onboard oven.
The rover’s sophisticated instruments detected the presence of thiophenic and aliphatic vapors when the samples were heated to temperatures ranging from 500° to 820° Celsius, which the researchers say are broken down elements of bigger organic molecules.
There is enough evidence, now, to suggest that Mars was not always as inhospitable as it is today, as the planet’s climate was conducive to the formation of liquid water – the elixir of life – on its surface.
Curiosity’s findings reveal that, in the far too distant past, a liquid water lake inside the Gale Crater had all the necessary building blocks to sustain life in one form or another.
“The Martian surface is exposed to radiation from space. Both radiation and harsh chemicals break down organic matter,” Eigenbrode said.
“Finding ancient organic molecules in the top five centimeters of rock that was deposited when Mars may have been habitable, bodes well for us to learn the story of organic molecules on Mars with future missions that will drill deeper,” added the NASA biogeochemist.
According to Rice University geologist Kirsten Siebach, the fact that we are able to find billions-of-years-old evidence of organic matter is a feat in itself.
“To me it is amazing that we can show we have organic matter preserved for more than 3bn years in these rocks,” she said.
“This is very promising for the preservation of potential ancient life on the planet,” she added.
Siebach also said that “these molecules could have been part of life, but they could also have been food for life,” going on to say that knowing that “the water really was full of organic molecules really opens up the different ways that life could have existed on Mars.”
Paul Mahaffy – study author and director of the Solar System Exploration Division at NASA’s Goddard Space Flight Center – said that “we have greatly expanded our search for organic compounds, which is fundamental in the search for life.”
Curiosity also found the presence of methane in the Martian atmosphere which fluctuates with the changing Martian seasons, tripling from 0.24 to 0.65 parts per billion, from winter to summer.
While announcing this discovery of a “repeatable, identifiable, seasonal pattern” in the methane levels, a senior research fellow at the Jet Propulsion Laboratory in Pasadena, California, Chris Webster said:
“Not only have we got this wonderful repeatability, but the seasonal cycle changes by a factor of three. That’s a huge change, completely unexpected.
And what it does, it gives us a key to unlocking the mysteries associated with Mars methane because now we have something to test our models and our understanding against.”
According to Webster, the seasonal fluctuation in methane concentrations is of great scientific significance because nearly all of the methane found on Earth is a biological by-product.
Also, the fact that methane does not last beyond a few centuries – breaking down or escaping into space over time – is exciting because the presence of the gas in the Martian atmosphere means that it could not be more than a few centuries old; further suggesting that methane is still forming.
Webster said that “if we see methane in the Martian atmosphere, that means something is happening today, it’s being released or it’s being created.”
While the presence of methane in the Martian atmosphere is not new knowledge, the recurrent pattern, discovered in its levels of concentration, definitely is.
The rise from a winter low of 0.24 parts per billion to a summer high of 0.65 parts, as mentioned before, is indicative of two possibilities; there are biological factors involved; or, the repeating pattern is simply the result of geological processes at work.
Regardless of its origin, Webster believes that the gas is trapped in the Martian sub-surface from where it escapes into the planet’s atmosphere.
“The idea that best fits our data is the idea of sub-surface storage. So way under the ground this methane is trapped, he said.
“We don’t know if that methane is ancient, we don’t know if it’s modern. It could be either. We also don’t know if that methane was created from rock chemistry or it was created by microbes,” Webster added.
“With these new findings, Mars is telling us to stay the course and keep searching for evidence of life,” said Thomas Zurbuchen – Associate Administrator for the Science Mission Directorate at NASA Headquarters.
“I’m confident that our ongoing and planned missions will unlock even more breathtaking discoveries on the Red Planet,” he predicted.