Finding extraterrestrial life isn’t necessarily as simple as looking for it with our eyes. A living thing might be too small to see, or too far away, or too different than what we expect to find. In addition to direct observation, we can also infer (deduce) the presence of life by looking at traces (clues) that a living thing leaves behind.

Detecting a favourable environment

• Living things have a checklist of requirements to live (for example: a solvent such as water, building blocks, an energy source).
• If we detect some of these required elements in an environment, we can infer that a lifeform might be able to live there.
• Detecting a favourable environment, however, is not proof that a lifeform lives there.