Radio Waves and Megastructures: Technosignatures Explained

If a signature is a unique mark that identifies someone, and if "bio" refers to life, then chemical clues in the air produced by living things are defined as biosignatures in atmospheres.

If plants and algae take in sunlight and carbon dioxide to make food, and if they release a specific gas as a byproduct of this process, then that gas is oxygen.

If certain gases react with each other and turn into new substances, then they cannot stay in the air for long; if we still see them there, then a constant source like life must be replacing them.

If methane and oxygen are like fire and ice that cancel each other out, then seeing them together is a sign that something active (like life) is pumping them into the air.

If different gases block specific colors of light, and if we split starlight into a rainbow after it passes through a planet's air, then the missing colors tell us which gases are there.

If life on Earth creates waste products as it grows and breathes, and if oxygen, methane, and nitrous oxide are common biological waste gases, then these are the targets for scientists.

If methane can also be produced by volcanoes or reactions between rocks and water, then finding the gas is only a hint; if it has non-living sources, it is not 100% proof of life.

If we cannot visit other stars yet, we must use the light that reaches us; if that light carries a chemical "fingerprint" from the planet's air, then we can identify life from a distance.

If we want starlight to shine through a planet's atmosphere so we can see the gases, then the planet must move directly between us and the star; this event is a transit.

If oxygen and methane naturally react to form water and CO2, then they should disappear; if they are both present, then "Planet Biology" must be working hard to create them both at once.

If a star is billions of times brighter than a planet, it is hard to see the planet's thin layer of air; if Earth's air also has oxygen, it can confuse the data from the telescope.

If a planet is a giant gas ball like Jupiter, it doesn't have a solid surface for life; if life needs a surface, then finding biosignatures is more likely on smaller, rocky planets like Earth.

If sunlight hits oxygen (O2) and turns some of it into ozone (O3), then finding ozone is a strong clue that a large amount of oxygen is present in the atmosphere.

If certain microbes inside animals break down food and release a gas as waste, and if that gas is a known biosignature, then the gas is methane.

If a "positive" result means finding life, and if "false" means the result is an error, then a gas made by a volcano that looks like a life-sign is a false positive.

If an atmosphere has the building blocks for life like water, carbon, and nitrogen, then the oxygen and methane signals are much more likely to be coming from a living ecosystem.

If plants on Earth reflect a lot of near-infrared light (which looks like a "red edge" in data), then seeing that same light pattern on another planet suggests it might have forests.

If "astro" means stars and "biology" is the study of life, then the science of looking for life in the stars is astrobiology.

If life as we know it needs liquid water, and if the habitable zone is the only place where it isn't too hot or too cold for water, then that is the best place to find life-gases.

If the JWST was designed with advanced infrared sensors to see through space dust and analyze the air of distant planets, then it is the primary tool for this research today.