Let’s Talk About Brines. No, Not That Kind.

The solar system is full of brines, and they're crucial to the search for extraterrestrial life.

An image of a pink salt lake
Aleksandr Maksimkin / Getty

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 brines on 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.

Brines are good natural places to search for life because salt can do some magical things to water. The presence of salt can prevent water from freezing in very cold temperatures—that’s why people salt their driveway before a snowstorm. “Salts allow liquid water to exist farther out in the solar system, so this expands the Goldilocks area in the solar system where life could exist,” Mohit Melwani Daswani, a geochemist and planetary scientist at NASA’s Jet Propulsion Laboratory, told me. And the longer a brine can remain unfrozen, the more stability the mixture provides to whatever life-forms might decide to inhabit it.

But as with any good recipe, there’s a balance, Daswani said. Too little salt and water could struggle to mingle with the other chemicals in the brine. Too much salt and there’s not enough water to participate in those chemical reactions, and any cell-based life-forms that might exist would dry out and break down. “There’s certainly a sweet spot somewhere,” he said.

That’s one of the goals of astronomy’s brine community: to figure out the conditions under which brines could produce life—the microbial kind, which we’re far more likely to detect than the advanced-civilization kind. We know that microbial life on Earth exists comfortably in weird places. “Most of the time when we go looking for life somewhere, even if it’s half a mile underneath the Antarctic ice shelf or buried in a subglacial lake or in a mine, we’re finding life there,” Jennifer Hanley, a planetary scientist at the Lowell Observatory, in Arizona, told me. For example, in the Atacama Desert in Chile, one of the planet’s best analogues for Mars, salt in the ground—plain old table salt—pulls moisture from the air on humid days. The water transforms into liquid droplets and, together with the salt, produces a tasty brine for the bacteria that live in the dry earth. The process is known as deliquescence, which sounds like it could be either a chemical reaction or a cooking technique.

Just like space brine, the perfect turkey brine also involves a bit of mystery, says Bill Nolan, a supervisor at the Butterball Turkey Talk-Line, a hotline that the poultry company has operated since the 1980s for Americans’ most pressing Thanksgiving-meal questions. The process can be tricky. “I’ve had people call up before and say, ‘I just realized my turkey’s been in the brine for two and a half days,’” Nolan told me. “When something’s too salty, it’s a little difficult to take that salt out of it.” Like the planetary scientists who warn that too much salt is bad for life, Nolan says that too much salt is bad for flavor.

So don’t oversalt your turkey, and don’t oversalt the solar system. Consider adding peppercorns to your turkey brine, as Nolan recommends, or candied ginger, as Hanley has done. Perhaps nature has also made some interesting additions to the brines beyond Earth, seasoning them with just enough elements so that a morsel of life can come into being.