Mars, one in all our closest planetary neighbors, has fascinated individuals for lots of of years, partly as a result of it’s so just like Earth. It’s about the identical dimension, accommodates comparable rocks and minerals, and isn’t an excessive amount of farther out from the Solar.
As a result of Mars and Earth share so many options, scientists have lengthy questioned whether or not Mars might have as soon as harbored life. As we speak, Mars could be very chilly and dry, with little ambiance and no liquid water on the floor − traits that make it a hostile surroundings for all times. However some observations counsel that historical Mars might have been hotter, wetter and extra favorable for all times.
Despite the fact that scientists observing the floor of Mars conclude that it was as soon as hotter than it’s at present, they haven’t been capable of finding a lot concrete proof for what brought on it to be hotter. However a research my colleagues and I printed in April 2025 signifies the presence of carbonate minerals on the planet, which might assist clear up this puzzle.
Carbonate minerals include carbon dioxide, which, when current within the ambiance, warms a planet. These minerals counsel that carbon dioxide might have beforehand existed within the ambiance in bigger portions and supply thrilling new clues about historical Mars’ surroundings.
As a geochemist and astrobiologist who has studied Mars for greater than 15 years, I’m fascinated by Mars’ previous and the concept that it might have been liveable.
Historical carbon cycle on previous Mars
Observations of Mars from orbiting satellites and rovers present river channels and dry lakes that counsel the Martian floor as soon as had liquid water. And these devices have noticed minerals on its floor that scientists can analyze to get an concept of what Mars might have been like previously.
As we speak, Mars could be very chilly, with a skinny ambiance and dry local weather. However within the historical previous, it could have been hotter and wetter, with a thicker heat-trapping ambiance.
NASA/J. Bell – Cornell U./M. Wolff – SSI through AP, File
If historical Mars had liquid water, it will have wanted a a lot hotter local weather than it has at present. Hotter planets normally have thick atmospheres that lure warmth. So, maybe the Martian ambiance was thicker and composed of heat-trapping carbon dioxide. If Mars did as soon as have a thicker carbon dioxide-containing ambiance, scientists predict that they’d be capable of see traces of that atmospheric carbon dioxide on the floor of Mars at present.
Gaseous carbon dioxide dissolves in water, a chemical course of that may in the end contribute to formation of stable minerals at and under the floor of a planet − primarily eradicating the carbon dioxide from the ambiance. Plenty of scientists have beforehand tried to search out carbonate minerals on the floor of Mars, and a part of the thrill a couple of hotter, wetter early Mars is that it might have been an acceptable surroundings for historical microbial life.
Discovering carbonates on Mars
Earlier searches for carbonates on Mars have turned up observations of carbonates in meteorites and at two craters on Mars: Gusev crater and Jezero crater. However there wasn’t sufficient to clarify a hotter previous local weather on Mars.
For the previous few years, the Mars Science Laboratory Curiosity rover has been traversing a area referred to as Gale crater. Right here, the rover’s chemistry and mineralogy instrument has found plenty of the iron-rich carbonate mineral siderite.
The Curiosity rover has detected carbonates on Mars’ floor.
NASA
As my colleagues and I element in our new research about these outcomes, this carbonate mineral might include a number of the lacking atmospheric carbon dioxide wanted for a hotter, wetter early Mars.
The rover additionally discovered iron oxyhydroxide minerals that counsel a few of these rocks later dissolved once they encountered water, releasing a portion of their carbon dioxide again into the ambiance. Though it is extremely skinny, the trendy Martian ambiance remains to be composed primarily of carbon dioxide.
In different phrases, these new outcomes present proof for an historical carbon cycle on Mars. Carbon cycles are the processes that switch carbon dioxide between totally different reservoirs − equivalent to rocks on the floor and fuel within the ambiance.
Potential habitats for previous microbial life on Mars
Scientists typically think about an surroundings liveable for microbial life if it accommodates liquid water; vitamins equivalent to carbon, hydrogen, nitrogen, oxygen, phosphorus, sulfur and obligatory hint components; an power supply; and circumstances that weren’t too harsh − not too acidic, too salty or too scorching, for instance.
Since observations from Gale crater and different areas on Mars present that Mars seemingly had liveable circumstances, might Mars then have hosted life? And if it did, how would researchers be capable of inform?
Though microorganisms are too small for the human eye to detect, they’ll go away proof of themselves preserved in rocks, sediments and soils. Natural molecules from inside these microorganisms are generally preserved in rocks and sediments. And a few microbes can kind minerals or have cells that may kind sure shapes. Any such proof for previous life known as a biosignature.
Accumulating Mars samples
If Mars has biosignatures on or close to the floor, researchers need to know that they’ve the fitting instruments to detect them.
To this point, the rovers on Mars have discovered some natural molecules and chemical signatures that would have come from both abiotic − nonliving − sources or previous life.
The Curiosity rover travels throughout Mars trying to find indicators that the planet might have as soon as been liveable.
Nevertheless, figuring out whether or not the planet used to host life isn’t simple. Analyses run in Earth’s laboratories might present extra readability round the place these signatures got here from.
To that finish, the Mars 2020 Perseverance rover has been accumulating and sealing samples on Mars, with one cache positioned on the floor of Mars and one other cache remaining on the rover.
These caches embrace samples of rock, soil and ambiance. Their contents can inform researchers about many facets of the historical past of Mars, together with previous volcanic exercise, meteorite impacts, streams and lakes, wind and mud storms, and potential previous Martian life. If these samples are delivered to Earth, scientists might look at them right here for indicators of historical life on one other planet.