Tracking Biosignatures in Alien Atmospheres
Stars are obscured by planets. We can examine the light spectrum that is emitted from a star when a planet passes in front of it using a method known as spectroscopy. There will be a color change that reveals the planet's spectrum as well as the gases that are necessary for the atmosphere of that planet to include in order to block off specific light frequencies.
In our experience, methane is a gas created by living organisms that is beneficial to life. A planet may support life if its atmosphere contains methane. In order to identify what gases are present in a planet's atmosphere and maybe whether it supports life, we can examine the light spectrum, remove light from the star that won't change, and filter out the light from the star.
There will be a lot of ground to cover in the search for life with thousands of exoplanets already detected and now, owing to the Webb telescope, tens of thousands more potentially on the horizon. To focus your search, seek for particular features like biosignatures, which are indications that a planet either supports life or has the potential to do so.
Even if oxygen is a no-brainer, the issue is not all or nothing, especially because we are aware that oxygen has only been present on Earth for a small portion of its whole duration. Instead, researchers have discovered tens of thousands of possible molecules that might be signs of life and that we might look for. Carbon dioxide, but not carbon monoxide, is another substance that may be a sign of life or at the very least, of habitability.
