Alien life likely can't survive on exoplanets smaller than Mars, scientists say
A rocky planet orbiting in the habitable zone of a sun-like star may look like a perfect place for life to thrive — but not if it's too small to hold onto its atmosphere. So, we may wonder: How much smaller Earth could be and still have its delightfully breathable atmosphere ? How small could an exoplanet be to sustain life as we know it? With these questions in mind, University of California Riverside planetary scientist Michelle Hill and her colleagues recently simulated what happens to the atmospheres of different sizes of rocky worlds. The worlds tested were similar to Earth and orbited in the habitable zones around sun-like stars . It turns out for a world to maintain an atmosphere long enough for life to gain a foothold (a few billion years at minimum), it needs to be at least as big as Mars . Narrowing down the search for life The habitable zone — the area around a star where tempera...