Science & Technology

A New Study Says Mars Was Once Covered in Enormous Rivers

We have more hope for life on Mars. Even though it's lost most of its atmosphere, and even though it's a dry place today, a new study suggests gigantic rivers flowed across the planet until 1 billion years ago. Maybe somewhere in all this water, life persisted.

Thin Atmosphere, Thick Water

Mars used to have a thick atmosphere, just like Earth. But Mars is a smaller planet and doesn't have a magnetic field. So when the sun's electrically charged particles hit the Martian atmosphere, individual molecules were carried off into space. Over eons, the atmosphere thinned.

Mars formed about 4.5 billion years ago and lost most of its atmosphere in only 800 million years. But rivers could have streamed across its surface long after that point. The study shows that there was plenty of flowing water between 1 billion and 3.7 billion years ago. That gives a lot of time for life to form and evolve.

This is an exciting find given that the Curiosity rover discovered extensive evidence of water runoff in its landing site of Gale Crater almost from the moment it landed in 2012. Turns out this "intense runoff production," as the scientists termed it in their Science Advances paper, "was not a short-lived or local anomaly. Rather, precipitation-fed runoff production was globally distributed, was intense, and persisted intermittently over 1 billion years."

Counting Rivers and Craters

The new information comes after lead author Edwin Kite, an assistant professor of geophysical sciences at the University of Chicago, and his colleagues looked at more than 200 ancient river systems using spacecraft that took images from orbit.

They figured out how old these rivers might be by counting craters in the ground surrounding the dried-up waterways. Scientists have estimates for how often meteors hit Mars and leave craters behind, so this is a common way to date terrain on Mars, the moon, and other worlds.

In this handout image supplied by the European Space Agency (ESA) on July 16, 2008, The Echus Chasma, one of the largest water source regions on Mars, is pictured from ESA's Mars Express. The data was acquired on September 25, 2005. An impressive cliff, up to 4000 m high, is located in the eastern part of Echus Chasma. Gigantic water falls may once have plunged over these cliffs on to the valley floor. The remarkably smooth valley floor was later flooded by basaltic lava.

The team found that the rivers are all over the planet. They don't know how much water these rivers carried, as that's the kind of information you find up close when you can see the rocks more clearly. However, the rivers' size suggests that they flowed for long periods and not just during Martian "high noon" when the weather is warmest and Martian ice is melting.

With more evidence than ever that water was persistent on the Red Planet, it makes us wonder: What was the climate like? Was there a lot of rainfall as well as flowing water on the surface? We'll probably need to update our models once again, and luckily there are more spacecraft on the way to help with the cause. Both NASA and a team of European and Russian scientists plan to send rovers towards the Red Planet in 2020.

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Written by Elizabeth Howell April 4, 2019

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