On 8 December 1990 the Galileo probe whizzed past Earth on it’s way to being slingshotted to its destination, the planet Jupiter. The astronomer Carl Sagan and others had the brilliant idea to turn Galileo’s camera and instruments on the Earth as it passed by. We know life exists here on Earth. What would show up in Galileo’s camera and instruments? Could we use that data to find life on planets orbiting distant stars? The result was a photo of the Australian desert with no obvious life or signs of civilization. But the instruments did find chemical traces of vegetation that we use today to find planets around distant suns that might harbor life.

Source: https://www.nature.com/articles/d41586-023-03230-z

Galileo Project Website: https://science.nasa.gov/mission/galileo/