The "chemical fingerprints" of 137 different species of microorganisms have been measured by a team of astronomers and biologists lead by Max Planck Institute for Astronomy (MPIA) graduate student Siddharth Hegde, according to a press release. Some of the microorganisms were taken from the most extreme environments on Earth and could help scientists identify biological colors on exoplanets. The team's results have been published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS).
Just as light reflects green on areas of vegetation on the Earth, biologists and astronomers are teaming up to focus on how to search for life on planets outside our solar system. Until now, indirect biosignatures have been used, but if a certain life form dominates a planet, the color reflected by the planet could indicate alien life.
Hegde, then a graduate student at MPIA, and astronomer Lisa Kaltenegger, the director of the Institute for Pale Blue Dots at Cornell University, teamed up with biologist Lynn Rothschild, a postdoctoral fellow Ivan Paulino-Lima and research associate Ryan Kent, all from the NASA Ames Research Center. The group collected 137 different species of microorganisms - 36 from existing culture collections, 100 samples assembled by Paulino-Lima and one isolated by Rocco Mancinelli of the BAER Institute at Ames. A diverse sample was crucial and a variety of environments were represented, including the Atacama desert in Chile, seawater in Hawaii and even some old woodwork at Salt Spring in Boone's Lick State Park in Missouri.
The biosignature catalogue created, which consists of reflectance spectra in the optical and near-infrared wavelength regions of the electromagnetic spectrum, 0.35-2.5 micrometers, according to the press release, is the most complete and diverse to date. It is also the first catalogue dedicated to exoplanets.
With current technology, it is not possible to directly measure light from an Earth-sized planet, because neighboring starlight drowns out any reflected colors, but Kaltenegger said in the press release, "this (database) gives us for the first time a glimpse into the detectable signatures of the fascinating diversity of worlds that could exist out there."
