Aliens — blink and you’ll miss ’em
Fragile life on other planets may never have survived infancy, new study suggests
The hunt for extraterrestrial life is one of humanity’s most exciting endeavours. The pieces are all falling into place: we’re finding more and more planets outside of our own solar system, and soon the James Webb Space Telescope will give us an unprecedented look at these distant worlds.
We’ve populated Mars with robots looking for signs of ancient habitability. Orbiters dive through the icy geysers of ocean-covered moons in hopes of catching some life-giving minerals. Our radio telescopes are tuned in to mysterious stars, listening for the sounds of a hustling and bustling civilization.
In spite all of that, we’ve yet to find a single measly microbe off-world. So where is everybody?
In a new study published in Astrobiology, researchers from the Australian National University offer up one possible explanation: maybe all of the other life in our neighbourhood has already come and gone.
It’s not a new idea. Space is big and time is long, so it’s likely that any life (intelligent or otherwise) would manage to miss us. It’s a standard answer to the Fermi paradox, which is the contradiction between the immense number of Earth-like planets and the apparent rarity of Earth-like life.
The new study goes a step further, suggesting that life, if it evolved, would often be too fragile to survive past its infancy.
In other words, it’s possible that other planets in our own solar system had blips of microbial life — tiny emergences that stood no chance of evolving into intelligent organisms.
In fact, you could blame climate change. But in this case, early organisms didn’t do enough to change their planet’s shifting climate.
“Most early planetary environments are unstable. To produce a habitable planet, life forms need to regulate greenhouse gases such as water and carbon dioxide to keep surface temperatures stable,” lead author Aditya Chopra said in a statement.
The study authors believe that Earth’s early microbial life helped to stabilize the planet’s climate, while any life that might have existed on the nearby, similarly rocky planets Venus and Mars failed to do so.
“Between the early heat pulses, freezing, volatile content variation and runaway positive feedbacks, maintaining life on an initially wet, rocky planet in the habitable zone may be like trying to ride a wild bull. Most life falls off,” the authors wrote in the study.
The researchers have named this phenomenon the “Gaian Bottleneck.” If it’s true, they point out, our lifehunting robots and astronauts will have to look for fossilized microbes of the most primitive sort. We’re not likely to find alien dinosaur bones.
“The mystery of why we haven’t yet found signs of aliens may have less to do with the likelihood of the origin of life or intelligence and have more to do with the rarity of the rapid emergence of biological regulation of feedback cycles on planetary surfaces,” Chopra said.