Ed Rivera-Valentín has spent quite a bit of time thinking about brines recently. The particular ratio of salt to water in the marinade. The special ingredients that can give things an extra kick.
I am referring, of course, to the salty solutions that are found across our solar system, on planets and moons and even asteroids. These would be no good on a Thanksgiving turkey, but they might be one of the most intriguing substances in the search for alien life. Last month, Rivera-Valentín, a planetary scientist at the Lunar and Planetary Institute, in Texas, and other scientists gathered for BrinesCon, the first of three conferences over the next few years devoted to brines. Some water, a pinch of salt—this is the kind of mixture that, under the right conditions, could give life a chance to burble into existence, Rivera-Valentín told me. “When we find life,” he said, “it’s likely going to be associated with a brine.”
Over the years, NASA has pursued a “follow the water” strategy when looking for alien life, dispatching spacecraft to search for traces of H2O on celestial bodies. But “you’re never going to find pure liquid water,” Rivera-Valentín said. “What you’re going to find are brines.” So when scientists search for water beyond Earth, they’re really looking for salty water. That’s where interesting things can happen. Life on Earth is believed to have formed in a primordial soup seasoned with salt, and our oceans today are just giant brines—and they’re teeming with life.
Even though we haven’t yet found evidence of life outside Earth, the rest of the solar system, it turns out, is quite salty. Spacecraft have discovered frozen brineson the surface of Mars and evidence of liquid ones that might exist deep underground. Saturn’s icy moon Enceladus has a briny ocean beneath its frigid crust. NASA spacecraft orbiting Saturn once even sampled some Enceladian brine when the material escaped from a crack in the ice and sprayed into space. In addition to salts, the passing spacecraft detected some organic compounds—not proof of life, but certainly an indication that the subsurface ocean could potentially host some form of it. Europa, another icy moon around Jupiter, has a briny ocean that occasionally spews into space too. And spacecraft data suggest that even Ceres, the largest object in the asteroid belt, might have small pockets of brine flowing deep within its interior.