In a new paper published in Nature, with lead authors from The University of Texas at Austin and the Planetary Science Institute, researchers found that some of the surface of Mars was shaped by massive floods that overflowed crater rims. These types of crater lakes are not unheard of here on Earth, and while most people are familiar with the more volcanic kind, we do also have examples of meteor craters with lakes. One of the most famous is Manicouagan in Quebec, Canada.

About 3.5 billion years ago, Mars had a lot of water on its surface, including large lakes, some of which were in impact craters. When the water levels got too high, the lakes burst over the crater rims and flowed down onto the flatter surface below, quickly carving out deep canyons. Again, similar flooding occurred here on Earth at the end of the last ice age, where lake waters burst through into the northwestern United States and Central Asia.

If it happens in one place, it happens in others, right? That’s one of those rules we use in geology and astronomy. An example of one leads to more examples. Such is the case with Mars.

This science is a result of analyzing mapped observations of Mars’s current surface and computer modeling to calculate the volume of the valleys. Those volumes were then compared with similar valley networks. PSI research scientist Alex Morgan explains: We found that at least a quarter of the total eroded volume of Martian valley networks were carved by lake breach floods. This high number is particularly striking considering that valleys formed by lake breach floods make up just 3% of Mars’ total valley length. This discrepancy is accounted for by the fact that outlet canyons are significantly deeper than other valleys. These floods would have shaped the overall Martian topography, affecting the flow paths of other valleys. Our results don’t negate the importance of precipitation-fed runoff on early Mars. On the contrary, liquid water had to be stable for long enough for lakes to fill from inlet rivers.

This was the first global analysis of lake overflow flooding done for Mars and helps to understand how the climate changed on Mars and whether it was “warm and wet” or “cold and icy”. I think we can safely say it was warm and wet now.

More Information

PSI press release

The University of Texas at Austin press release

“The importance of lake breach floods for valley incision on early Mars,” Timothy A. Goudge, Alexander M. Morgan, Gaia Stucky de Quay and Caleb I. Fassett, 2021 September 29, Nature