1. Embrace the cold. Here on Earth, life requires liquid water for its essential operations. But on the surface of Mars, where temperatures seldom get higher than -70°C, water is perpetually frozen. This means that any microbes burrowed into the Martian permafrost may have the ability to quench their thirst with a liquid that has a lower freezing point. No life has yet been found on the Red Planet, but recently, a team of scientists suggested that an organism capable of combining hydrogen peroxide with a small amount of water might survive such cold, dry conditions.
2. Live in a cloud. One layer of Jupiter’s vast atmosphere is a haze of ammonia, ammonia hydrosulfide, and water—all smeared by the planet’s swift rotation into frayed wisps the size of continents. An article published in the 1960s by the American Astronomical Society (coauthored by Carl Sagan) hypothesized that organisms living in that layer might look like tiny hydrogen-filled balloons. They might reproduce asexually via exploding seeds or spores, or, like raindrops, they might coalesce with others of their kind and become larger organisms. The atmosphere of Jupiter might harbor great living dirigibles, each of them many miles across.
3. Sip methane. On Saturn’s large moon Titan, the warmest midday temperature is about -179°C. Still, if we could walk along a Titanian lake, we might see foaming waves lapping gently at a pebbled shore. If we stayed very long we would learn that the pebbles are water-ice as hard as granite, and that the surf is methane. Methane is the same liquid that carved Titan’s river channels and falls as its rain. Some scientists who study Saturn and its moons say that if there is Titanian life, methane might be its drink of choice.
4. Find a comet. Astronomers think of comets as “dirty snowballs,” fragments of ice and rock dusted with organic matter. As a comet falls along its orbit toward the sun, its surface layers boil off. Any ice locked inside its dark interior melts, and for a few days or weeks—as long as it’s warm enough—any hibernating microbes would have liquid water to help them begin to move and reproduce.
5. Think electrically. The central character of The Black Cloud, a 1950s-era science fiction novel by astronomer Fred Hoyle, isn’t a human; it’s a diffuse nebula of hydrogen and more complex molecules. Organized in the manner of a living being, The Black Cloud propels itself by manipulating magnetic fields and thinks with electrically charged dust particles.
6. Slip into a parallel universe. Atoms are composed of particles called protons and neutrons, and protons and neutrons, in turn, are composed of quarks. Change the masses of quarks even slightly, and you couldn’t make atoms like those we know. Simple chemistry—let alone biology—would be impossible. But in 2009, a team of physicists found that if you adjust masses of quarks in a certain way, you might make atoms with neutrons and a particle called Σ –, or “sigma minus.” A universe with such atoms could have hydrogen, carbon, and oxygen, the elements necessary for life as we know it.
7. Go with the flow. What are life’s most basic needs? No one really knows, but it’s possible that they are nothing more than matter and energy, and it’s possible that any sort of matter and energy will do. As for the shapes life might take, there may be no limits at all. One scientist has proposed that, over billions and billions of years, life might “evolve into whatever material embodiment best suits its purposes.” If he’s right, then in the long run the best way to survive in outer space, or even right here on Earth, is simply to stay open to change.