Mars was once a ‘planet of rivers’, but could they have harboured life?

Mars is one of the best candidates for finding extraterrestrial life (or traces of life from billions of years ago) in our solar system. It’s no surprise, then, that researchers have long focused their exploration efforts on our neighbouring planet, sending various spacecraft to investigate before humans touch down for a closer look in person. This week, NASA’s Curiosity rover turned up some new results.

The fresh findings come from scientists who examined data collected by the rover at Gale crater, a huge basin where an ancient meteor is thought to have made impact with the martian surface. In a statement, they say that they’ve discovered new evidence that Mars used to be covered in rivers, which could once have harboured life.

“We’re finding evidence that Mars was likely a planet of rivers,” says Benjamin Cardenas, assistant professor of geosciences at Penn State, and lead author on the paper announcing the discovery. “We see signs of this all over the planet.”

The research didn’t just involve looking at Martian soil via photos beamed back by Curiosity (though that did play a part). The scientists also brought satellite data of the planet, as well as 3D scans of rock beneath the seafloor back on Earth – originally created by oil companies in the Gulf of Mexico – into the mix. Together, these helped them to come up with a computer model that simulated the erosion of Mars over many millennia.

Using this simulation, the researchers came to the conclusion that common crater formations on Mars — known as bench-and-nose landforms — are most likely the remains of ancient riverbeds, built up over long periods of the planet’s history. Although some previous evidence has pointed to the past existence of water on Mars, it hasn’t typically been considered as the cause of such geological features. 

“This suggests that there could be undiscovered river deposits elsewhere on the planet, and that an even larger section of the martian sedimentary record could have been built by rivers during a habitable period of Mars history,” says Cardenas. This has some exciting implications for the possibility of extraterrestrial life, as well: “On Earth, river corridors are so important for life, chemical cycles, nutrient cycles and sediment cycles. Everything is pointing to these rivers behaving similarly on Mars.”

Some more Mars news has emerged in the last week, however, which might dampen the spirits of anyone expecting to leave Earth behind and find some new friends on the Red Planet. According to a pair of papers in Nature, the core of Mars is smaller than we previously thought. The reason for our miscalculations? It’s actually coated in a sea of molten, radioactive rock about 100 miles deep, which may be a leftover from a time when the whole planet was coated in one big churning magma ocean.

If this hypothesis proves true, then it could explain why Mars isn’t surrounded by an active magnetic field, like Earth. This is what protects us from radiation from space, like solar winds, which could have a disastrous effect on a rocky planet without the same protection – some believe it could even explain why there’s no visible life walking around on Mars to this day.

Aliens or not, all of the new discoveries about Mars offer an intriguing glimpse into the planet’s past and present, which could help shed light on Earth’s evolution later down the line. “This analysis is not snapshot, but a record of change,” Cardenas adds. “What we see on Mars today is the remnants of an active geologic history, not some landscape frozen in time.”