The ingredients for life arespread throughout the universe.
We are two scientists who studyexoplanetsandastrobiology.
The hope is that one or more of these planets will have a chemical signature of life.
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These measurements can give astronomers information on the mass and size of an exoplanet, but not much else.
Earths biosignature was very faint during this early era.
That changed abruptly2.4 billion years agowhen a new family of algae evolved.
This selective trapping of wavelengths of light is why objects are different colors.
Leaves are green because chlorophyll is particularly good at absorbing light in the red and blue wavelengths.
The pattern of missing light is determined by the specific composition of the material the light interacts with.
It could also be used to detect peculiar colors on the surface of a planet.
These pigmentsproduce characteristic colorsthat can be detected by using a sensitive infrared camera.
For now, the only telescope capable of such a feat is the newJames Webb Space Telescope.
It also can only detect changes toatmospheric levels of carbon dioxide, methane and water vapor.
This idea is similar to using your hand to block sunlight to better see something in the distance.
Futurespacetelescopes could use small, internal masks or large, external, umbrella-like spacecraft to do this.
Once the starlight is blocked, it becomes much easier to study light bouncing off a planet.
Animals, including cows, produce methane, but so do many geologic processes.
Image: Jernej Furman/Wikimedia Commons, CC BY
Is it biology or geology?
Photosynthesis produces oxygen, but sunlight does, too, when it splits water molecules into oxygen and hydrogen.
There is agood chance astronomers will detect some false positiveswhen looking for distant life.
