Life in the Solar System Likely Exists and is More Common Than We Think

The asteroid Ceres, currently being explored by the spacecraft Dawn, may contain an ocean deep underground. NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Updated | It's one of the most compelling questions humanity has tried to answer: Is there life beyond Earth? Scientists are closer than ever to answering that question, thanks to a host of technological advances and each new spacecraft that launches—and sometimes even thanks to evidence falling right onto our laps.

Evidence like two meteorites that crashed into Earth in 1998. Nestled within those space rocks were tiny bright blue salt crystals, and inside of those crystals were tiny pockets of extraterrestrial water filled with organic compounds, the building blocks of life, according to new research published on Wednesday.

"I think it's likely" that there is other life within our solar system, first author on that work, Queenie Chan, a planetary scientist at Open University in the U.K., told Newsweek. And even better, she says, we're doing the science that might finally find it. "That's why we like searching missions, isn't it?"

That means missions like NASA's Dawn spacecraft, which has been studying the largest object in the asteroid belt, the dwarf planet Ceres. Chan and her co-authors believe the salt crystals they studied may have first been formed on Ceres or a similar object, so they have paid close attention to the results the Dawn spacecraft has gathered. That includes identifying sodium chloride, better known as table salt, and sulfur dioxide. "When I saw them I was like, 'Hey, I saw that in our sample too,'" she said.

Although the Dawn mission will end later this year, there are plenty of successors on the way, like Europa Clipper, NASA's plan to fly by Jupiter's icy moon after a 2020s launch. Scientists suspect that it could host life, thanks to the theory that the moon is hiding a giant salty ocean and volcanic activity under its icy shell. Life—as we know it, anyway—requires water, common chemicals like oxygen and carbon dioxide that scientists think could be forming on Europa's icy shell, and an energy source (on Earth, that's usually the sun, but on Europa it could be geological processes).

Chan says her new research supports these suspicions of life on Europa because the story she and her colleagues put together for the salt crystals they studied relies on conditions also believed to exist on this moon. In particular, they think the crystals found within the meteorite were shot off a particularly water-rich asteroid by cryovolcanism, a type of geologic activity that spews water or ice instead of lava.

Scientists suspect the cryovolcanism may occur on Europa as well. And unlike traditional geologic activity, these eruptions don't reach high temperatures that would irreparably toast these life-supporting chemicals. "Our study proves that, ok, this kind of scenario is similar to what we found on the meteorite," Chan said of scientists' hypotheses about what's happening on Europa. "It is likely that inside this ocean world there is a whole wide range of chemical compounds."

Read more: Ancient Meteorites That Crashed to Earth Carried Ingredients for Life, Including Water and Organic Compounds

Or consider Mars, currently the playground of science robot extraordinaire, Curiosity. We have a few precious pieces of Mars here on Earth in the form of Martian meteorites, which can be analyzed for the same basic compounds Chan went looking for in her asteroid-born samples. One of the key types of compounds scientists look for is amino acids—the building blocks of life—which Chan and her colleagues did find.

But even more exciting would be a particular subset of amino acids. Each type of amino acid comes in two flavors, which scientists call left- and right-hand forms. Living things only use the left-handed versions, called homochirality—those are the amino acids scientists hope to find as an indication of alien life.

The problem is, it's ridiculouslyeasy to contaminate meteorites here on Earth, so scientists don't feel confident about the results they would get from such an analysis. On Mars, it's a different story. "If they find homochirality of amino acids, that would be phenomenal," Chan said of the Curiosity mission.

Chan says that all told, she thinks it's likely there's life tucked away somewhere else in the solar system waiting to be found. And if you expand the scope beyond our solar system, the odds of life existing get even better. "It's easier to say that, the universe is so big," she said.

Whether in our own neighborhood or beyond, scientists are looking for the same criteria. They may be rare, but they should be out there somewhere. "You have to have the right conditions," Chan said. "A lot of boxes have to be ticked to make that feasible."

This story has been updated to correctly identify Europa.