It seems ever more apparent, that the ingredients for life are spread throughout the universe. While Earth is the only known place in the universe with life, detecting life beyond Earth is a major goal of modern astronomy and planetary science.
Thanks in large part to next-generation telescopes like James Webb, researchers like us will soon be able to measure the chemical makeup of atmospheres of planets around other stars. The hope is that one or more of these planets will have a chemical signature of life.
Life might exist in the solar system where there is liquid water-like the subsurface aquifers on Mars or in the oceans of Jupiter’s moon Europa.
Searching for life in these places is incredibly difficult, as they are hard to reach and detecting life would require sending a probe to return physical samples.
Many astronomers believe there’s a good chance that life exists on planets orbiting other stars, and it’s possible that’s where life will first be found.
To detect life on a distant planet, astrobiologists will study starlight that has interacted with a planet’s surface or atmosphere. For the first half of its existence, Earth sported an atmosphere without oxygen, even though it hosted simple, single-celled life.
As it began science operations in July 2022, James Webb took a reading of the spectrum of the gas giant exoplanet WASP-96b. The spectrum showed the presence of water and clouds, but a planet as large and hot as WASP-96b is unlikely to host life.
Webb was not designed to search for life, so the telescope is only able to scrutinize a few of the nearest potentially habitable worlds. While certain combinations of these gasses may suggest life, Webb is not able to detect the presence of unbonded oxygen, which is the strongest signal for life.
Even using the most powerful telescopes of the coming decades, astrobiologists will only be able to detect strong biosignatures produced by worlds that have been completely transformed by life.
Most gases released by terrestrial life can also be produced by nonbiological processes-cows and volcanoes both release methane. There is a good chance astronomers will detect some false positives when looking for distant life.
The next generation of exoplanet studies has the potential to pass the bar of the extraordinary evidence needed to prove the existence of life.