New analysis of sediment samples collected by the rover revealed the presence of carbon – and the possible existence of ancient life on the Red Planet is a possible explanation for why it may be.
That is why carbon atoms – along with their recycling cycle – are tracers of biological activity on Earth. So they could be used to help researchers find out if there was life on ancient Mars.
When these atoms are measured inside another object, such as the Mars sediment, they can shed light on a planet’s carbon cycle, no matter when it occurs.
Learning more about the origin of this newly discovered Mars carbon may reveal the process of carbon rotation on Mars.
Secrets in the sediment
Curiosity landed in August 2012 in the Gale crater on Mars. The 96-mile (154.5 km) crater, named after Australian astronomer Walter F. Gale, was created by a meteorite impact between 3.5 billion and 3.8 billion years ago. The Great Pit once contained a lake, and now it covers a mountain called Mount Sharp. The groove also includes layers of exposed ancient rock.
For a closer look, the rover drilled between August 2012 and July 2021 to collect sediment samples across the crater. Curiosity then heated these 24 powder samples to 1,562 degrees Fahrenheit (850 degrees Celsius) to separate the elements. This led to the models releasing methane, which was then analyzed by another instrument in the rover’s arsenal to show the presence of stable carbon isotopes or carbon atoms.
Some samples were reduced to carbon and others were enriched. Carbon consists of two stable isotopes, measured as carbon 12 or carbon 13.
“Samples depleted of carbon 13 are similar to those taken from sediment 2.7 billion years old in Australia,” said Christopher H. Schmidt, professor of geology and principal research professor at Pennsylvania State University. House said in a statement.
“Those patterns were caused by biological processes when methane was consumed by ancient microbes, but on Mars we can not necessarily say because it is a planet made up of different materials and processes than Earth.”
In lakes on Earth, microorganisms like to grow in large colonies, which mainly form mats under the water surface.
3 Possible carbon origin
The different measurements of these carbon atoms can say three different things about ancient Mars. The origin of carbon may be due to cosmic dust, the ultraviolet decay of carbon dioxide, or the ultraviolet decay of biologically produced methane.
“These three scenarios are unusual in that they are not normal processes on Earth,” the researchers said.
According to House, the first scene involves our entire solar system passing through a galactic dust cloud, which occurs every 100 million years. Particle-heavy cloud triggers cold events on rocky planets.
“It doesn’t put a lot of dust in,” House said. “It’s hard to see any of these deposition events on the Earth record.”
But during such an event, the cosmic dust cloud may have lowered the temperature of ancient Mars, which may have contained liquid water. This will cause glaciers to form on Mars and dust on top of the ice. As the ice melts, the sedimentary layer, including carbon, stays in place. Although this is entirely possible, there is little evidence for glaciers in the Gale Greater, and the study authors said it would require further research.
The second scenario involves the conversion of carbon dioxide on Mars into organic compounds such as formaldehyde due to ultraviolet radiation. That hypothesis requires further research.
The third way this carbon is produced has potential biological roots.
Methane has the potential to leave traces of carbon on the surface of Mars in contact with ultraviolet light.
Further drilling on the horizon
The Curiosity rover will return to the site where most of the samples were collected in about a month, which will allow another opportunity to analyze the sediment from this mysterious location.
“This research fulfills the long-term goal of Mars exploration,” House said. “To measure different carbon isotopes – one of the most important geological instruments – from the sediments of another habitable world, it does so after nine years of research.”
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