Illustration of an icy exoplanet. An international team of researchers have created a color catalog … [+]
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Fluorescent green algae blooms and cheerfully pink watermelon snow — also the result of algae — are just two examples of the many brightly pigmented microorganisms on Earth’s surface, which are found in abundance in the Arctic and Antarctica.
Ice is an extreme environment for life to survive in and these bright microbes can be spotted on Earth’s surface by satellites. This combination of factors gives way to the idea that if these microorganisms exist on other planets which are covered in ice, their biopigments could be spotted by our telescopes.
In a newly published paper, an international team of researchers present a color catalog of microorganisms which thrive in icy environments on Earth. The database could be used to recognize signs of microbial life on frozen, rocky planets and moons outside our solar system, called exoplanets and exomoons.
“We are giving the first tool for searching for life on icy exoplanets,” said Lígia Coelho, first author on the paper and an astrobiologist pursuing her Ph.D. at the Instituto Superior Técnico in Portugal.
The researchers created the catalog by taking the reflection spectra of 80 microorganisms isolated from ice and water collected in the subarctic climate region of Canada. Reflection spectra measurements are used to reveal information about the color and brightness of the subject of study.
Coelho collected the 80 microorganisms used for the study back in February 2019 while on a research trip in Kuujjuarapik, Quebec. The small Canadian community, only accessible by air, sits at the mouth of the Great Whale River which is a tributary of the Hudson Bay.
To gather the samples, Coelho walked out onto the frozen over Hudson Bay and collected ice cores which she brought back to Portugal where the microorganisms were separated from the ice and water. Then, the samples were taken to Upstate, New York to be tested in laboratories at the Carl Sagan Institute at Cornell University.
The reflection spectra measurements taken in the research labs revealed crucial information on what the microbes would look like when viewed from our telescopes.
When you imagine an ice-covered landscape, you likely picture it as pure white. Despite this assumption, Coelho said, “the diversity of colors and pigments is astonishing.”
The subarctic microorganisms revealed an array of colors from orange to yellow to pink to green. The researchers also found that the dried samples had more intense colors than their fresher counterparts. This could mean that drier exoplanets have stronger signatures and would be better targets for astronomers to find biopigments.
“These biopigments are relevant because although they are representing just microniches here on Earth, they could cover entire planets elsewhere,” said Coelho.
In the future, ground-based and space telescopes could look at the atmospheres of icy, rocky exoplanets and exomoons for the vibrant microbes. The Large Ultraviolet Optical Infrared Surveyor or LUVOIR, a space telescope concept which is currently in development by NASA, could look at the surfaces of these exoplanets for the biopigments cataloged in the research.
The research may also be extended in the future to other types of exoplanets as well.
