What Mars can tell us about searching for aliens elsewhere

Contributed by
Dec 17, 2017

If there really is anything crawling around Mars, it hasn’t emerged yet, but conditions on the Red Planet could help us figure out the possibility of aliens lurking on another planet.

NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) mission is using Mars as an extraterrestrial lab for investigating how habitable rocky exoplanets may be. MAVEN’s instruments have been zeroing in on the chemical and physical processes behind Martian atmospheric escape, and the data it has beamed back to Earth suggests that the sun’s temper tantrums in the form of solar storms, solar flares, and coronal mass ejections have been behind this atmospheric annihilation.

How much of Mars’ remaining atmosphere gets away depends on what mood the sun is in. What the MAVEN research team wanted to know was whether the same would happen if a planet like Mars were orbiting a red dwarf star, otherwise known as an M-star.

“The MAVEN mission tells us that Mars lost substantial amounts of its atmosphere over time, changing the planet’s habitability,” said MAVEN co-investigator David Brain, a professor at the Laboratory for Atmospheric and Space Physics at the University of Colorado Boulder. “We can use Mars, a planet that we know a lot about, as a laboratory for studying rocky planets outside our solar system, which we don’t know much about yet.”

Brain and his team imagined this hypothetical exoplanet was orbiting within the habitable zone, which would have to be much closer to its star since M-stars are relatively dim. It would have to float around at about the distance Mercury is from the sun. Unfortunately, that and an M-star’s extreme UV wavelengths also mean this planet would get radiation-bombed 5 to 10 times more than Mars does, and Mars already gets ravaged enough by killer plasma.

More starlight means more energy to supercharge the processes that would wear away at the atmosphere of such an exo-Mars. It would experience up to 5 times the ion escape, or loss of charged particles. Thermal escape, or the loss of lighter molecules (such as hydrogen) at the edge of the atmosphere, could increase if a sudden blast of UV radiation were to send more hydrogen rocketing away.

Brain's hypothetical exoplanet and M-star could look something like this. Credit: NASA/JPL-Caltech

It gets worse. That same radiation would dismember molecules in the upper atmosphere and mean 5 to 10 times the photochemical, or neutral particle, escape. Enter the process of sputtering. Those molecules would be broken into charged particles that would then zoom into the atmosphere and create chaos by bumping some molecules into each other and others into space.

Obviously, if life—at least as we know it—has no chance on the surface of Mars, then don’t expect anything with nine eyeballs to be leering at you from a similar planet orbiting an M-star.

But wait. What if you could factor in things Mars is missing, such as a magnetic field, which would act as protection from stellar winds that would otherwise strip the atmosphere, or active geological processes that could act as replenishing forces after atmospheric escape? Just the planet’s being larger would mean more gravity to hang on to an atmosphere that would otherwise vanish.

“Habitability is one of the biggest topics in astronomy, and these estimates demonstrate one way to leverage what we know about Mars and the Sun to help determine the factors that control whether planets in other systems might be suitable for life,” MAVEN principal investigator Bruce Jakosky said.

So maybe there is such a planet out there, but don’t expect aliens. Yet.

(via NASA)