Published: Fri, June 08, 2018
Research | By Wilma Wheeler

Organic matter found on Mars in 'significant breakthrough'

Organic matter found on Mars in 'significant breakthrough'

In 2020, NASA plans to launch a rover that will seek out organics and search for chemical signatures of life in ancient Red Planet rocks.

The United States National Aeronautics and Space Administration on Thursday announced that its Curiosity rover has found complex organic matter preserved in ancient sediments that formed a vast lake bed on lower Mount Sharp onMars more than three billion years ago.

The material was found after the rover drilled into the surface of a 3.5 billion-year-old mudstone at the bottom of the Gale crater.

That said, the agency hopes future missions to the red planet, NASA's Mars 2020 rover and ESA's ExoMars rover, could delve into these findings and reveal the complete history of our neighboring planet.

Curiosity has also found increasing evidence for seasonal variation of methane on Mars - indicating the source of the gas is likely the planet itself, or possibly its subsurface water. "As NASA put it, Water-rock chemistry might have generated the methane, but scientists can not rule out the possibility of biological origins".

Curiosity drilled down and found the evidence in the top five centimetres of rock, a surprise given that the surface of Mars is hammered by radiation from space, and over time the light would break down organic matter.


That may be because numerous compounds, such as thiophene, methanethiol and dimethyl sulfide, had sulfur atoms in their molecular structure - which would strengthen the relatively fragile organic molecules, allowing them to survive the radiation bombarding the planet's surface for so long.

The discoveries, reported today in two papers in the journal Science, while not evidence of life, provide more tantalising clues about what's happening on Mars, for future missions to investigate.

"These clathrates lock the methane inside a water-ice crystal structure and are incredibly stable for millions of years until environmental conditions change and suddenly they can release that gas", says Duffy. "That doesn't mean life, but organic compounds are the building blocks of life", he added. And life as we know it requires organic molecules to exist. Curiosity reports that methane levels on Mars go up and down in a predictable cycle. The rock samples were analyzed by SAM, which uses an oven to heat the samples (in excess of 900 degrees Fahrenheit, or 500 degrees Celsius) to release organic molecules from the powdered 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.

In 2013, SAM detected some organic molecules containing chlorine in rocks at the deepest point in the crater.

Seasonal changes in methane at Gale Crater. Also pleasing is that the presence of chlorine and sulphur, which both preserve organics, suggests the presence of many more deposits from which to learn more about Mars' past and possible ecosystems. One explanation "that no one talks about but is in the back of everyone's mind", as Goddard planetary scientist Mike Mummaput it to Science last winter, is that methanogens beneath the Martian surface were breathing it out. "It had the ability to support life-but doesn't mean life were there". "And it makes us more confident that if biomarkers" - or direct evidence of biologic activity - "are there, we might find them". Mars doesn't recycle its rock the way that Earth does-maybe its ancient dust can teach us a thing or two about our own planet's history, said Siebach. They're considered necessary for life to form, but there are plenty of places with lots of organic compounds but no life.

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