And in his opinion, the best place to search for a potential second tree of life is on Mars — either in the form of past life documented in ancient rocks once exposed to water or the discovery of living environments hidden deep underground.
“There’s a lot of evidence that standing bodies of water persisted on the surface of Mars in the distant past,” Flannery says. “If there was life there 4 billion years ago, it seems reasonable to assume that we might have a vestige of it today in a protected refuge,” one that’s isolated from the harsh conditions found on the arid surface of the Red Planet.
The best-known example of this kind of protected ecosystem is what’s called Earth’s deep biosphere, an extensive network of microorganisms encased in solid rock down to about 6 miles (10 km) underground. Due to the similarities in the early histories of Earth and Mars, Flannery says, “If I was looking for extant life in the solar system, I’d go to Mars and I would drill.”
By reaching into progressively deeper layers of Mars, investigators may first encounter spores associated with a relatively recent geological era. And by going to even greater depths, they might even find fully vegetative microbes.
But no matter what they find, Flannery points out that with the Perseverance rover slated to launch for Mars next month, “we’re about to investigate rock types that are known for preserving biosignatures on Earth — [those rocks] that date from this early phase of martian history — for the first time.”
However, one burning question still remains: What will happen if a space agency discloses the discovery of alien life?
It is certainly possible that the realization that earthlings are not the only life-form out there will be kept under tight wraps, at least until details can be clarified. But one can still hope that such an announcement — if and when it goes public — could be celebrated as the glue that unifies our lonely, anxious species in these trying times.
The discovery of extraterrestrial life, if it ever happens, just may present the perfect opportunity for humans to take a step back from our earthly divisions, forcing us to reframe our dissonant voices into a singular, planet-wide harmony.
Michael Shilo DeLay and Anastasia Bendebury are co-founders of the scientific literacy organization Demystifying Science.