Mars today is a cold, dry wasteland. But billions of years ago it probably looked very different there. Since the start of robotic missions to Mars in the 1970s, scientists have been collecting clues that point to a warmer, wetter past for the Red Planet. One whose surface was full of lakes and oceans that might be alive. This is one of the reasons NASA built a new rover and recently sent it on its way to look for signs of prehistoric aliens.
However, there is no full consensus on what Mars really looked like in the past. “The controversy over the climate of early Mars is old,” says Anna Grau Galofre of Arizona State University. She is the main author of a new study published in the journal “Nature Geoscience“Was published and turns the dreams of a watery Mars upside down. In it, she presents new evidence suggesting that the ancient landscape of the planet looked more like Antarctica than the tropics. For example, many geological features are believed by researchers to have been carved out by flowing rivers and waterways that replenish frequent rainfall. But they may be due to massive glaciers and ice sheets that have melted over time.
The new study focuses on the history of the valleys in the southern highlands of Mars. “Previous work has shown that rivers are the origin of the Mars valley networks,” says Grau Galofre. In their investigation, however, some systems were identified for the first time with features that are “typical of subglacial canals”. That said, it was melting ice and not running water that dug these valleys nearly 3.8 billion years ago.
Canals on Mars
The research team examined 10,276 valleys belonging to 66 valley networks on Mars and grouped them using tailor-made algorithms to find out what type of erosion processes they formed. They then compared these results with terrestrial valleys formed by subglacial channels in the Canadian Arctic.
The main difference between networks of rivers and networks of melted ice is due to the way water flows. Rivers can only cut valleys out of rock only when the water runs downhill. However, subglacial channels are under pressure, allowing the melted water to flow uphill as well. The researchers’ models can detect tell-tale signs of the direction of the water and infer the likely cause.
Grau Galofre’s team found that 22 of the valley networks appear to have been carved out by subglacial meltwater, 14 by river water and the rest by other erosion processes. If the authors are correct, “this would suggest that Mars was mostly cold at the beginning of its history,” says Jay Dickson, a planetary scientist at Caltech who was not involved in the study. Some Climate models came to the same conclusion, which contradicts the prevailing image of ancient Mars as a planet covered with oceans and lakes.
A cool planet
However, the new findings do not mean that Mars was a giant ice ball in the past. Joe Levy thinks the results are food for thought. However, the geologist from Colgate University, who was not involved in the study, notes that the research “struggles to pinpoint a single process responsible for creating each valley”.
“This smear in the data could be because there wasn’t a single process that created all of the Martian valleys,” he says. “If you have a few billion years to work with it, it’s very likely that Every valley has experienced everything from glacial erosion to lava flows to floods under silver skies. Each of these processes changes the shape of the valley network and leaves behind a series of superimposed features. “
Fortunately, cool Mars doesn’t mean bad news for the possibility that life once existed there. “The subglacial environment could have provided a stable environment – with readily available water, a temperature without large vibrations and protection from energetic solar particles and from radiation without the need for a magnetic field,” says Grau Galofre.
We already know that life can survive such cold environments. This is proven by organisms that live under the Antarctic ice cover in places like Lake Vostok. Possibly this was also possible on Mars, even in these subglacial channels. Dickson believes the new findings will push researchers to study other parts of Mars as well.
“On Mars there are hundreds of very large dry lakes from this period that contained large amounts of meltwater from these valley networks,” he says.
This includes the landing pad for the NASA Perseverance rover, which will arrive at Jezero Crater next February, and that mission could potentially create space to look for such evidence. “It’s an exciting challenge for the entire Mars science community,” says Dickson.