Nasa's Curiosity rover detects signs of past life on Mars

Nasa’s Mars rover, Curiosity, might have found the building blocks of life on the Red Planet.

Research has found that rocks collected by the rover reportedly contained organic carbon which may have come from bugs that once roamed Mars.

Analysis of sediments from half a dozen locations, including an exposed cliff, identified an ancient carbon cycle. The samples are thought to have a ‘biological basis’, resembling fossilised remains of microbial life in Australia that date back 2.7 billion years.

Carbon has two stable isotopes, 12 and 13, the amounts of which give us a window into its origin.

‘The samples extremely depleted in carbon 13 are a little like samples from Australia taken from sediment that was 2.7 billion years old,’ said Professor Christopher House, the lead author of the study from Penn State University in the US.

‘Those samples were caused by biological activity when methane was consumed by ancient microbial mats. But we can’t necessarily say that on Mars because it’s a planet that may have formed out of different materials and processes than Earth,’ he said.

On Earth, it would indicate past microbes consumed microbially produced methane. Methane — the simplest organic molecule — is known to be present in Mars’ atmosphere.

Ancient Mars may have had large plumes of methane being released from the subsurface where production would have been energetically favourable.

Then, the released methane would either be consumed by microbes or react with ultraviolet light and be deposited directly on the surface.

Curiosity has been roaming the Gale Crater for over nine years — drilling under the surface and sending the results back home.

The Gale Crater is believed to have been a deep lake 3.5 billion years old, containing complex organic molecules which are key raw materials for life as we know it.

‘The amounts of carbon 12 and carbon 13 in our solar system are the amounts that existed at the formation of the solar system. Both exist in everything, but because carbon 12 reacts more quickly than carbon 13, looking at the relative amounts of each in samples can reveal the carbon cycle,’ said House.

Curiosity heated the samples in the absence of oxygen to separate any chemicals. Scans showed some were exceptionally depleted in carbon 13 while others were enriched.

Other plausible theories include a cosmic dust cloud – or ultraviolet radiation breaking down carbon dioxide.

‘All three of these scenarios are unconventional – unlike processes common on Earth,’ said House.

He believes that finding the remains of microbial mats could clear things up.

Nasa’s rover, Perseverance, which landed last February is currently drilling Mars’ Jezero crater — the site of another ancient lake — for signs of past life.

‘We are being cautious with our interpretation, which is the best course when studying another world,’ said House.

Curiosity is still collecting and analysing samples. It will be returning to the site where it found some of the samples in about a month.

For the scientists, the findings accomplished a long-standing goal for Mars exploration to measure different carbon isotopes — one of the most important geology tools — from sediment on another habitable world.

The study was published in the Proceedings of the National Academy of Sciences.

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