LICHENS and algae could be the first life forms we find on Earth-like exoplanets, by looking for their light signatures in a planet’s distinctive colouring.
Seen from space, Earth gives off a large amount of near-infrared light, which is reflecting off the chlorophyll in plants. As telescopes get more sensitive, it should be possible to see a similar “red edge” on distant exoplanets if they also host green vegetation.
But Siddharth Hegde and of the Max Planck Institute for Astronomy in Heidelberg, Germany, think it is possible that many rocky worlds will have extreme heat, dryness or acidity, and that hardier life forms will dominate their surfaces. So what would these organisms look like from a distance?
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To find out the pair looked at the light reflected by some of Earth’s more extreme life forms: lichens in arid regions, bacterial mats in very hot water and red algae in acid mine drainage. They calculated that seen from afar each type of organism would create a unique colour pattern. Lichens, for instance, appear more yellow than the algae or bacteria (Astrobiology, ).
This article appeared in print under the headline “Extreme life can colour rocky worlds”