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The Mars Double Attack

Dark, narrow streaks on Martian slopes such as these at Hale Crater are inferred to be formed by seasonal flow of water on contemporary Mars.
Dark, narrow streaks on Martian slopes such as these at Hale Crater are inferred to be formed by seasonal flow of water on contemporary Mars.

This is Mars week.

First, we had the mindboggling announcement that there is strong evidence of liquid water flowing on the Martian surface. And, also this week, on Oct. 2, the much-awaited Riddley Scott movie, The Martian -- based on Andy Weir's novel and starring Matt Damon as an astronaut stranded on Mars — opens nationwide. It seems that the red planet won't play second fiddle to the moon, especially a blood red one.

Starting with the science, the paper "Spectral Evidence for Hydrated Salts in Recurring Slope Lineae on Mars," was published in Nature Geoscience on Sept. 28. In it, the authors analyze the composition of recurring dark streaks surrounded by brighter terrain, suggestive of the presence of moisture. Think about how wet concrete is darker than dry concrete. Using spectroscopic techniques, the scientists found traces of hydrated salts in all streaks (lineae) investigated, showing that the phenomenon coincides with warmer weather: Mars warms up, water flows down the slopes, carrying salts with it. Mind you, these are no waterfalls, just somewhat moister soil.

High salinity helps water to remain liquid even at very low temperatures. For example, Don Juan Pond in Antarctica, the saltiest known body of water on the planet with salinity above 40% (18 times higher than ocean salinity and 9.6 times higher than the Dead Sea), has liquid water at temperatures of -22 ºF. But no life.

The excitement of finding liquid water on Mars is related to the correlation between water and life. If we want to find life on other planets, a great starting point is to first find water. Unfortunately, high salinity is not good for life. Even so, there may be variations in the saline content of different streaks, and some may be lower. As always with a new possibility, we will only know if we look.

Looking depends on sending a rover with the appropriate instruments, something that is not in NASA's plans for now. There is danger of contamination, that is, of the instrument itself bringing the life we want to find. In such high stakes questions, we certainly don't want to be fooled, especially if Martian life has similar properties to life on Earth.

Too bad Matt Damon is not up there to give us a hand. (Spoiler alert!) He manages to survive much longer than his supplies last by reengineering the Martian soil, making it produce the food he needs. The whole Earth unites in trying to bring him back home, not without dramatic strife, of course, as the movie explores a new take on our unity as a species.

Heroes are not just those who fight in wars but those who help expand what it means to be human — astronauts and scientists included. Let us hope that our first human exploration of the red planet is less tragic — and not too far away in the future.

Marcelo Gleiser is a theoretical physicist and cosmologist — and professor of natural philosophy, physics and astronomy at Dartmouth College. He is the co-founder of 13.7, a prolific author of papers and essays, and active promoter of science to the general public. His latest book is The Island of Knowledge: The Limits of Science and the Search for Meaning. You can keep up with Marcelo on Facebook and Twitter: @mgleiser.

Copyright 2021 NPR. To see more, visit https://www.npr.org.

Marcelo Gleiser is a contributor to the NPR blog 13.7: Cosmos & Culture. He is the Appleton Professor of Natural Philosophy and a professor of physics and astronomy at Dartmouth College.