Instead of solar energy, their world is fueled by a unique chemical synthesis triggered by hot water boiling out from the Earth's crust. Similarly, microbes live within the boiling waters of hot springs such as in Yellowstone Park. Other organisms thrive in small pockets of salty soup locked within polar ice. Then there are basalt formations such as those in Eastern Washington, where microscopic creatures have found ways to survive and flourish deep inside, drawing energy from the natural weathering of the rock. Many scientists are betting it does.
Most people think of Mars as a barren planet, but there is evidence of subsurface water.
NASA in December launched a mission trying to find that vital liquid of life. Europa, an icebound moon of Jupiter, is providing new clues that there might be volcanoes and liquid water beneath its frozen cloak. In October, scientists began seeing similar signs on Callisto, an icy sibling of Europa. The essentials for life are liquid water and available energy, which can be harvested from a number of sources other than sunlight, including chemical, thermal and tidal processes. It's not just the discovery of life in those extreme conditions on Earth, but a growing understanding of how intemperate conditions must have been when life emerged here.