Earth's Changing Colors Could Help Us Find Alien Life

[Judi Lynn]

By Mike Wall 11 hours ago Search For Life

We're learning more about how to hunt for ET in all its potential forms.



To understand where exoplanets are in their own evolution, astronomers can use Earth’s biological milestones as a Rosetta stone.(Image: © Illustration by Wendy Kenigsberg/Cornell Brand Communications)


Earth's color palette has changed considerably over time, and that fact could help astronomers better understand the evolution of other life-hosting planets, a new study suggests.

In 1990, NASA's Galileo Jupiter probe studied Earth in detail during the first of two speed-boosting flybys of our planet. This project, the brainchild of famed astronomer Carl Sagan, was designed to hone future searches for alien life, by showing scientists which "biosignatures" they could feasibly target on distant worlds.

And Galileo delivered. The spacecraft, which reached Jupiter's orbit in December 1995, spotted multiple signs of life, including Earth's "red edge" — a sharp reflectance jump at near-infrared wavelengths of light. The red edge is a signature of vegetation: The photosynthesizing pigment chlorophyll absorbs most visible light but is transparent to longer wavelengths, and plants therefore bounce that part of the electromagnetic spectrum back to space (perhaps to avoid overheating).

But the red edge has not always appeared as the Galileo spacecraft saw it. After all, the feature is produced today in large part by terrestrial vegetation — but land plants have been around for just 500 million years or so, more than 3 billion years after life began on Earth.

More:
https://www.space.com/alien-life-search-expanded-photosynthesis-signatures.html