Meanwhile, scientists studying Lake Vida in Antarctica have discovered a rich bacterial ecosystem in its frigid, briny water, considerably extending the definition of 'hospitable to life'. At -13 °C, Lake Vida has been locked beneath a cap of ice twenty metres thick for almost three thousand years, permanently dark and lacking free oxygen. Without light and photosynthesis, the microbes need some other energy source. It's possible that they can utilise energy produced by chemical reactions between the briny water and iron-rich sediments, so that, unlike most ecosystems on Earth, they don't need organic material ultimately produced by capturing sunlight. Which has obvious implications for the kinds of life that may exist in brines that might be found deep beneath the Martian surface, or in the cold and sunless oceans under the icy surfaces of moons like Jupiter's Europa, Saturn's Enceladus, or Neptune's Triton. But it's also possible that the microbes have been ekeing out a living by scavenging a bare residue of dissolved carbon compounds. Which makes me wonder if there might not be icy worldlets in the outer reaches of the solar system, or in dust and debris belts around other stars, whose subsurface oceans are intermittently penetrated by meteorites. As the ice around the impact site seals over, there's a sudden blooming of life as microbes and other organisms - meteorphages - compete for organic material dissolving in the frigid brine, frantically growing and reproducing until the material is exhausted. The brief meteor spring is over, and everything switches to survival mode and shuts down, waiting for the next impact in a thousand or ten thousand years . . .