Important progress has been made in our understanding and use of biomarkers, the signatures astronomers use to search for life in space. The work is all the more important given budget constraints that have cancelled space missions complementing the biomarker work by identifying life friendly star systems; improved biomarker searches may make up for fewer supporting missions.
Astronomers still hope to revive some version of Terrestrial Planet Finder [artist’s rendering below], but it would take a decade for the mission to get back on track, Marcy estimates. In the meantime studies by exoplanet researchers including Sara Seager of the Massachusetts Institute of Technology and Victoria Meadows of the University of Washington in Seattle are honing—and expanding—the list of compounds that may serve as biomarkers for exoplanets orbiting stars of different sizes and ages.
With the chances of looking for chemical markers of life beyond the solar system initially few and far between, “we want to make sure we have the best possible understanding of bio-signatures,” Meadows says. “We don’t want to be fooled.”
Much of the new work focuses on planets orbiting M dwarf stars, which are about one-half to one-tenth the sun’s mass and account for about 75 percent of all the stars in the galaxy. Because M dwarfs are much cooler than the sun, their habitable zones are only about one tenth as far from them as Earth lies from the sun.
The recent work on biomarkers, as well information about the cancellation of and existing plans for relevant space missions, are covered in my latest feature article for Scientific American.