The question of life on Mars is made all the more frustrating by our understanding that Mars once was a wet world with oceans, rivers, and warmer temperatures. If Mars was able to have all the things necessary to life and we don’t find any evidence for life, it hints that life doesn’t form easily but doesn’t necessarily prove anything. If we find evidence of past life absolutely everywhere, it means life does form easily. And if we actually find life, that means that life does find a way, even on a desert world like Mars.

The surface water that once graced Mars’ surface seems to have literally blown away in the wind. Well, more like in the winds: the wind of Mars and the solar wind. 

Dust storms on Mars can drive low-altitude water vapor and humidity to the upper layers of Mars’ atmosphere. Once there, ultraviolet light from the Sun is capable of breaking apart water molecules into hydrogen and oxygen. Hydrogen molecules, unfortunately, don’t have a lot of mass, and in collisions with other particles, they can pick up crazy amounts of velocity. They can, in fact, be accelerated to escape velocities through collisions either with other atmospheric particles or with particles from the solar wind. Without that now-escaped hydrogen, water molecules can’t reform, and over time, Mars was literally stripped of its water.

We knew that upper atmospheric collisions could liberate lightweight particles. What we didn’t know was how water was getting lifted from the lower atmosphere to the upper atmosphere. Now we know – the answer is dust.

While dust storms on Earth don’t decimate our water the same way, we do see the same kind of loss of lightweight particles. Helium is the one that is most worrisome. 

Helium is often liberated during different mining processes, and then used for a variety of tasks, including the cooling of medical and scientific equipment. When that helium is released into the atmosphere instead of carefully captured and reused, the helium is able to accelerate to escape velocities through collisions. This means that all that helium that escaped from party balloons literally escaped the Earth. Helium is a non-renewable resource and it’s possible that someday, we’re going to run out of helium here on Earth. So, maybe don’t have helium party balloons?

More Information

NASA Goddard press release

“Martian water loss to space enhanced by regional dust storms,” M. S. Chaffin et al., 2021 August 16, Nature Astronomy