Understand the real ways of searching for life — from analyzing the atmospheres of exoplanets to listening for radio signals — and take a sober look at what we have found so far.
How we sniff distant planets
The search for life: what we can really do
We can't yet fly to other stars — they're too far away. So life is searched for from a distance, and there are several approaches.
— Analyzing atmospheres. When a planet passes in front of its star, the starlight filters through the planet's atmosphere and reveals what its air is made of. Scientists are especially interested in “biosignatures” — gases that life gives off on Earth (for example, oxygen together with methane). Finding them together would be a serious clue. The James Webb Space Telescope does just that.
— Listening to space (the SETI program). Huge radio antennas listen to the sky in case they catch an artificial signal from another civilization. So far — silence.
— Searching in the solar system. Life (at least simple, microbial life) is also sought next door: on Mars, and in the subsurface oceans of Europa (a moon of Jupiter) and Enceladus (a moon of Saturn) — there is liquid water under their crust of ice.
The honest bottom line today: we have NOT found convincing traces of extraterrestrial life — no microbes, no signals. But we've only just started looking seriously, and there are billions of planets in our galaxy alone. The physicist Enrico Fermi famously asked: if life is common, then “Where is everybody?” There's no answer yet.
Lesson notes
The search for life: what we can really do
We can't yet fly to other stars — they're too far away. So life is searched for from a distance, and there are several approaches.
— Analyzing atmospheres. When a planet passes in front of its star, the starlight filters through the planet's atmosphere and reveals what its air is made of. Scientists are especially interested in “biosignatures” — gases that life gives off on Earth (for example, oxygen together with methane). Finding them together would be a serious clue. The James Webb Space Telescope does just that.
— Listening to space (the SETI program). Huge radio antennas listen to the sky in case they catch an artificial signal from another civilization. So far — silence.
— Searching in the solar system. Life (at least simple, microbial life) is also sought next door: on Mars, and in the subsurface oceans of Europa (a moon of Jupiter) and Enceladus (a moon of Saturn) — there is liquid water under their crust of ice.
The honest bottom line today: we have NOT found convincing traces of extraterrestrial life — no microbes, no signals. But we've only just started looking seriously, and there are billions of planets in our galaxy alone. The physicist Enrico Fermi famously asked: if life is common, then “Where is everybody?” There's no answer yet.