Curiosity has discovered ancient organics that have been preserved in rocks for billions of years. Source: NASA Goddard
Nasa's Curiosity rover has uncovered signatures of an environment on the red plant that may once have been habitable.
In two studies on data collected by the Mars rover over the past few years, scientists have identified an abundant source of organic matter in the ancient soil, and traced some of the planet's atmospheric methane to its roots.
The findings could help to guide the search for ancient microbial life and improve our understanding of seasonal processes on Mars.
Nasa revealed details on the latest findings in a press conference Thursday afternoon.
The announcement may not be the detection of life itself, but the findings address factors that are "fundamental to our search for life", explained Paul Mahaffy, director of the Solar System Exploration Division at Nasa's Goddard Space Flight Centre, during the conference.
The organic molecules identified in the Curiosity samples were found in rocks from an ancient lakebed, explained lead author and astrobiologist Dr Jennifer L. Eigenbrode.
The rover extracted and heated samples from Mojave and Confidence Hills in the Gale Crater, both of which are known to contain mudstones dating back roughly three billion years.
This revealed the presence of molecules that resembled organic-rich sedimentary rock found on Earth, according to the team, including thiophene, 2- and 3-methylthiophenes, methanethiol and dimethylsulfide.
"Those organic molecules could have come from life," Eigenbrode said, "but we don't know that there was ever life on Mars. So those specific molecules are not evidence of life."
Instead, the researcher explained, these molecules could be traced to non-life sources, such as meteorites.
"What were looking at here are a lot of layers that were put down in an ancient lake," Eigenbrode said during the press conference, addressing the as-yet-unknown origins of the newly detected organic matter.
"That lake had been there for a long time - hundreds of thousands, maybe millions of years.
"Organic materials can come into that lake through rivers, they can be windblown in, or they can be formed in the lake itself through biology," Eigenbrode continued.
"One source could be meteorites, or rock forming processes that form organics on their own.
"We don't have enough information from the observations we've made to know what the source is, and how it got in there."
The Mars curiosity rover was initially intended to be a two-year mission to help answer if the planet could support life, has liquid water, and to study the climate and geology.
According to the researcher, these molecules detected on Mars differ by a single carbon sidechain from those seen on Earth, suggesting they may be fragments of larger organic molecules.
Although the discovery may not mean Curiosity has found evidence of ancient life on Mars just yet, it is a promising step forward ahead of missions that plan to dig even deeper into the Martian soil and a "good sign" of the planet's ancient habitability, the researchers say.
"The new findings reinforce our conclusions that there is Martian organic matter in the ancient sediments and they tell us about how the organic molecules are preserved in the rocks," Eigenbrode told MailOnline.
"The detection of organic matter in rocks from an ancient habitable environment on Mars bodes well for the future search for life on Mars.
"Organic matter could come from life, but the presence of organics is not evidence for life since organics can also come from non-life processes," said told MailOnline.
"We found organic matter in rocks exposed at the surface where the environment is very harsh and tends to break down organic matter.
"Finding it in this harsh place means we might find better preserved organic matter in other places, particularly where it has not been exposed to lots of radiation.
"To do this, we might drill deep, which is what ESA's ExoMars rover plans to do.
"Alternatively, we could look for outcrops that have been recently excavated by erosion or meteorite impacts.
"Perhaps Nasa's Mars2020 mission will have this opportunity and will cache samples for return to Earth."
In addition to the discovery of organic materials, the Curiosity data also reveal new clues on the origins of Mars' mysterious methane.
Methane is known to exist in the scant Martian atmosphere, but how it got there has remained a mystery.
On Earth, the compound is linked to biological sources – meaning it's closely tied to the presence of life.
But on Mars, scientists have proposed numerous other abiotic processes that could have given rise to the methane.
In the second of the two new studies, researchers used measurements of atmospheric methane captured by the Curiosity rover to better understand its origins.
With 80kg of scientific instruments on board, the rover weighs a total of 899kg and is powered by plutonium.
The rover is 2.9m long by 2.7m wide by 2.2m in height.
The rover was initially intended to be a two-year mission to gather information to help answer if the planet could support life, has liquid water, study the climate and the geology of Mars.
Because of its success, the mission has been extended indefinitely and has now been active for more than 2000 days.
The rover has several scientific instruments on board, including the mastcam, which consists of two cameras and can take high-resolution images and videos in real colour.
So far, the car-sized robot has encountered an ancient streambed where water used to flow, not long after it also discovered that billions of years ago, a nearby area known as Yellowknife Bay was part of a lake that could have supported microbial life.
