Here's how to find aliens

A team of scientists has created a colorful catalog containing reflection signatures of Earth life forms that might be found on planet surfaces throughout the cosmic hinterlands, giving us a better chance to learn if we are not alone.

Cornell University's Lisa Kaltenegger said that this database gives humans the first glimpse at what diverse worlds out there could look like. They looked at a broad set of life forms, including some from the most extreme parts of Earth.

The scientists explained that much of the history of life on Earth has been dominated by microbial life, adding that it is likely that life on exoplanets evolves through single-celled stages prior to multicellular creatures. Here, they present the first database for a diverse range of life, including extremophiles (organisms living in extreme conditions) found in the most inhospitable environments on Earth, for such surface features in preparation for the next generation of telescopes that will search for a wide variety of life on exoplanets.

To spot the tint of Earth, alien astronomers from Andromeda might measure light shimmering off the surface of a planet, as sunlight reflected from our planet's vegetation reaches their telescopes. Conversely, astronomers here can see pigmentation on exoplanets and determine their makeup by looking at their color.

On Earth these are just niche environments, but on other worlds, these life forms might just have the right make to dominate, and now we have a database to know how we could spot that, said Kaltenegger.

The group has gathered the cultures of 137 cellular life forms that range from Bacillus gathered at the Sonoran Desert to Halorubrum chaoviator found at Baja California, Mexico, to Oocystis minuta, obtained in an oyster pond at Martha's Vineyard.

Lead author Siddharth Hegde said that their results show the amazing diversity of life that one can detect remotely on exoplanets, adding that they explore for the first time the reflection signatures of a diversity of pigmented microorganisms isolated from various environments on Earth, including extreme ones, which will provide a more broad guide, based on Earth life, for the search for surface features of extraterrestrial life.

The study appears in the Proceedings of the National Academy of Sciences.