Q: Just curious if you believe there is life out there on another planet besides Earth. (Tom McDonnell, Birdsboro, Pa.)
I believe we’ll soon find life right here in our own solar system. Mars once had a warm, Earth-like climate, with a protective atmosphere and liquid water on the surface. Microbes from these early days might still survive on Mars in today’s harsh conditions by inhabiting hot springs or in warm aquifers and rocks below the surface, where there is energy, water, and probably organic material—the conditions for life as we know it.
Europa, a moon of Jupiter, and Enceladus, a moon of Saturn, have oceans of liquid water below their icy crusts. In these dark oceans, warmed by the tidal tug of their parent planets, life might exist in the mix of organic chemicals deposited there by impacting asteroids and comets. If we don’t find life in our own solar system, our Milky Way galaxy has an estimated eight billion Earth-sized worlds that orbit in their parent stars’ habitable zones—that region where liquid water can exist on a planet’s surface. I like those odds.