Carbon discovered in Martian sediments by NASA’s Curiosity rover has three plausible origins — including being a chemical trace of ancient microscopic life.
This is the conclusion of Pennsylvania State-led experts, who said the carbon may also have come from cosmic dust or the ultraviolet breakdown of carbon dioxide.
According to the bacterial theory, methane is produced underground by microorganisms and then broken down on reaching the surface by ultraviolet radiation.
Researchers explained that all three scenarios are “unconventional” in the sense they’re not like other processes on Earth.
Curiosity landed on Mars on August 6, 2012 — and since has been roaming around Gale Crater collecting and analysing rock samples, relaying the data back to Earth.
There have been several carbon-rich sediments found from ancient Martian locations.
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Carbon discovered in Martian sediments by NASA’s Curiosity rover (pictured) has three plausible origins — including being a chemical trace of ancient microscopic life
Carbon has two stable isotopes — C¹² and C¹³ — with the ratio between the two offering insights into a given sample’s history.
“The amount of carbon-12, and carbon-13 found in the solar system is equal to what existed before.” [its] formation,’ said paper author and geologist Christopher House of the Pennsylvania State University.
“Both are present in all things, however, carbon-12 reacts faster than carbon-13 so comparing the amounts in different samples may reveal the carbon cycle.
The carbon found by Curiosity — which has the capacity to drill samples out of the ground and subject them to chemical analysis — found extreme variations in C¹²/C¹³ ratios depending on where the sediment samples were collected.
Some deposits appear to be exceptionally depleted in C¹³, while other samples were highly enriched instead.
Here on Earth, the presence of a strongly C¹³-depeleted signature from an ancient surface would be considered indicative of the production of methane by subsurface bacteria — with such broken down by ultraviolet radiation at Mars’ surface.
Professor House said that the samples with extremely low carbon-13 levels are similar to samples taken from Australia’s sediment that is 2.7 billion years old.
“Those examples were due to biological activity, when methane was consumed ancient microbial matrixes. But we don’t know if that’s true on Mars. Mars may have been formed from different materials and processes that Earth.
The carbon found by Curiosity — which has the capacity to drill samples out of the ground and subject them to chemical analysis — found extreme variations in C¹²/C¹³ ratios depending on where the sediment samples were collected. Pictured is the Highfield drilling hole that Curiosity made to obtain a sample of Vera Rubin Ridge in Gale crater.
According to the researchers, another explanation for the depletion of C¹³ in the carbon analysed by Curiosity lies in how the solar system traverses a vast molecular cloud every couple of hundred years.
Professor House explained that this passage is difficult to find in Earth’s geoological records because the cloud “doesn’t deposit much dust.”
For enough to have been concentrated in a layer that the Curiosity rover could sample, the galactic dust cloud would have first have to lower the temperature of Mars’ surface — which at that time still sported liquid water — to create glaciers.
The hypothesis is that the snow would have remained on top of these glaciers after melting.
There is not much evidence to support the idea that Mars’ Gale Crater once had been glaciated. The team stated that this explanation was plausible but requires more research.
The final explanation put forward by the team for the C¹³-depleted samples involves the ultraviolet radiation-driven conversion of carbon dioxide into compounds like formaldehyde.
Professor House stated, “There are papers which predict that UV could cause such a type of fractionation.”
“However, further experimental evidence is needed that shows this fractionation. This will allow us to either rule it in or eliminate this explanation.
Some deposits analysed by Curiosity appear to be depleted in C¹³, while other samples were highly enriched instead. Pictured: The Stimson sandstone formation in Gale crater — near where the rover made the Edinburgh drill hole that yielded a C¹²-enriched a sample
‘All three possibilities point to an unusual carbon cycle unlike anything on Earth today — but we need more data to figure out which of these is the correct explanation,’ said Professor House.
He said, “We are cautious about our interpretation. This is the best course of action when studying other worlds.”
“It would be great if the Rover could detect large plumes of methane and take measurements from them. However, there is not enough methane plumes to measure isotopes and most plumes are too small for measurement.
The geologist said that the discovery of glacially-derived sediments and microbial mats would help to clarify the situation.
On Mars, the Curiosity rover is still working to collect and analyse rock samples — and, in fact, will be returning to the pediment where it found the carbon-bearing sediments of concern in this study in around one month’s time
On Mars, the Curiosity rover is still working to collect and analyse rock samples — and, in fact, will be returning to the pediment where it found the carbon-bearing sediments of concern in this study in around one month’s time.
Professor House stated that this research had achieved a long-held goal of Mars exploration.
This, he explained, has been ‘to measure different carbon isotopes — one of the most important geology tools — from sediment on another habitable world, and it does so by looking at nine years of exploration.’
Full results of the study are published in Proceedings of National Academy of Sciences.
THE NASA MARS CURIOSITY ROVER LAUNCHED IN 2011 AND HAS IMPROVED OUR UNDERSTANDING OF THE RED PLANET
Initial launch of the Mars Curiosity Rover was from Cape Canaveral on November 26th 2011, an American Air Force Station in Florida.
After embarking on a 350 million mile (560 million km) journey, the £1.8 billion ($2.5 billion) research vehicle touched down only 1.5 miles (2.4 km) away from the earmarked landing spot.
The rover made a successful landing in August 2012 and has now traveled approximately 11 miles (18 kilometers)
It launched on the Mars Science Laboratory (MSL) spacecraft and the rover constituted 23 per cent of the mass of the total mission.
With 80 kg (180 lb) of scientific instruments on board, the rover weighs a total of 899 kg (1,982 lb) and is powered by a plutonium fuel source.
The Rover measures in at 2.9 m (9.9 ft), 2.7 m (8.9ft), and 2.2 metre (7.2 ft).
The Mars curiosity 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 an has since been active for more than 2,000 days
In the beginning, the mission of the Mars Rover was to last two years. The goal was to collect information that could help determine whether Mars can support life and if Mars has water.
Because of its success, it was extended indefinitely. It has been operating for over 2000 days.
There are many scientific instruments aboard the rover, such as the mastcam (two cameras) that can capture high-resolution images in true colour.
The car-sized robot has so far encountered an old streambed through which liquid water once flowed. Not long afterwards, it discovered that a Yellowknife Bay, located nearby, was once part of a lake, that may have been able to support microbial life, shortly after its discovery.