Mars May Have Been Habitable Longer Than Thought

A NASA-funded simulation of past Mars has revealed that the red planet was wetter for 500 million years longer than previously thought, giving life more time to develop.

IMAGE: This conceptual image reveals what the Kasei Valles region on Mars may have looked like three billion years ago. White areas are glaciers and blue represents ocean. CREDIT: F. Schmidt/NASA/USGS/ESA/ DLR/FU Berlin (G. Neukum)

When we think of Mars, we think of a red planet, barren, covered in dust and rocks and ancient lava flows. There’s an ongoing debate about the existence of liquid water under the polar ice caps. We’ve tracked seasonal changes with a host of satellites. And we have a small collection of rovers wandering the surface, sampling, analyzing, and collecting rocks. There are sedimentary rocks that were clearly created due to the flow of water. We’ve seen pictures of stream channels and river deltas, and Perseverance landed in what we think was an ancient crater lake bed.

And yet, no life. Granted, Percy is the first rover really tasked with looking for signs of life*, and even it’s not allowed to sample where we think life could still be if it were there. We seem, on the whole, to be hopeful that we’ll find evidence of life or past life because of that wet history of Mars, even if most of the water is gone, whether it has escaped the thin atmosphere or gone underground.

Now, in a new paper published in the Proceedings of the National Academy of Sciences, a NASA-funded simulation of past Mars has revealed that the red planet was wetter for longer than previously thoughts — about 500 million years longer. The research into Mars’ past conditions is not an easy task, as co-author Michael Way explains: Discerning the climate of Mars approximately three billion years ago is challenging because the Martian surface features do not seem to fully support either a warm and wet or cold and dry climate during that time. A warm and wet climate would have produced extensive erosion from flowing water, but few valley networks have been observed from this age. A too-cold climate would have kept any northern ocean frozen most of the time. A moderate cold climate would have transferred the water from the ocean to the land in the form of snow and ice. But this would prevent tsunami formation, for which there is some evidence.

This new simulation found not only a cold and wet Mars was possible, but there might have…