In the search for life beyond Earth, the “astromobile” Curiosity NASA, the American space agency, is on a nearly decade-long mission to determine whether Mars was once habitable for living organisms.
A new analysis of sediment samples collected by the rover has revealed the presence of carbon – and the possible existence of ancient life on the red planet is just one potential explanation for why it exists.
Carbon is the foundation of all life on Earth, and the element cycle is the natural process of recycling carbon atoms. On our home planet, carbon atoms go through a cycle as they travel from the atmosphere to the ground and back into the atmosphere.
Most of our carbon is in rocks and sediments and the rest is in the ocean, atmosphere and organisms, according to NOAA, the National Oceanic and Atmospheric Administration.
This is why carbon atoms – with their recycling cycle – are markers of biological activity on Earth. Thus, they could be used to help researchers determine whether life existed on Mars.
When these atoms are measured inside another substance, such as Martian sediment, they can shed light on a planet’s carbon cycle, no matter when it occurred.
Learning more about the origin of this recently detected Martian carbon could also reveal the element’s cycling process on Mars.
A study detailing these findings was published Monday in the journal Proceedings of the National Academy of Sciences.
Secrets in the sediment
O Curiosity landed in Gale Crater on Mars in August 2012.
The 154.5 kilometer crater, named after Australian astronomer Walter F. Gale, was likely formed by a meteor impact between 3.5 billion and 3.8 billion years ago.
The large cavity likely once housed a lake and now includes a mountain called Mount Sharp. The crater also includes layers of exposed ancient rocks.
For a closer look, the rover drilled to collect sediment samples in the crater between August 2012 and July 2021.
Curiosity then heated these 24 dust samples to around 850 degrees Celsius to separate the elements. This caused the samples to release 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 of the samples were carbon depleted, while others were enriched. Carbon has two stable isotopes, measured as carbon 12 or carbon 13.
“The extremely carbon 13-depleted samples are a bit like samples from Australia taken from 2.7 billion-year-old sediments,” Christopher H. House, lead author of the study and a professor of geosciences at Pennsylvania State University, said in a statement. .
“These samples were caused by biological activity when the 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 from different materials and processes than Earth.”
In Earth’s lakes, microbes like to grow in large colonies that essentially form mats just below the water’s surface.
Three possible sources of carbon
The varying measurements of these carbon atoms can suggest three very different things about Mars’ past.
The origin of carbon is likely due to cosmic dust, ultraviolet degradation of carbon dioxide or ultraviolet degradation of biologically produced methane.
“All three of these scenarios are unconventional, unlike common processes on Earth,” according to the researchers.
The first scenario involves our entire solar system passing through a cloud of galactic dust, something that occurs every 100 million years, according to House. The cloud of heavy particles can trigger cooling events on rocky planets.
“It doesn’t deposit much dust,” House said. “It’s hard to see any of these deposition events in Earth’s record.”
But it’s possible that during an event like this, the cosmic dust cloud lowered temperatures on Mars, which could have liquid water.
This may have caused glaciers to form on the red planet, leaving a layer of dust on top of the ice. When the ice melted, the layer of sediment, including carbon, would have remained.
While it is entirely possible, there is little evidence of glaciers in Gale Crater and the study authors said this would require further research.
The second scenario involves converting carbon dioxide on Mars into organic compounds, such as formaldehyde, due to ultraviolet radiation. This hypothesis also requires additional research.
The third way this carbon was produced has possible biological roots.
If this kind of depleted carbon measurement were done on Earth, it would show that microbes were consuming biologically produced methane.
although the Curiosity has already detected methane on Mars, researchers can only guess if there were once large clouds of methane being released under the surface of Mars. If that were the case and there were microbes on the Martian surface, they would have consumed this methane.
It is also possible that the methane interacted with ultraviolet light, leaving a carbon trail on the Martian surface.
More drilling on the horizon
The Curiosity rover will return to the location where it collected the most samples in about a month, which will allow another chance to analyze sediment from this intriguing location.
“This research has achieved a long-standing goal for the exploration of Mars,” House said. “To measure different isotopes of carbon – one of the most important geology tools – from sediments in another habitable world, and it does so by looking at nine years of exploration.”
This content was originally created in English.
Reference: CNN Brasil