“Channeling Carl Sagan” –Asteroid-Bound Spacecraft Finds Earth Teeming With Life and Scary Climate Change

 

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Nearly 30 years ago, the Galileo spacecraft flew past Earth on its journey to Jupiter, prompting astronomer Carl Sagan to develop a novel experiment: to look for signs of life on Earth from space. The spacecraft found high levels of methane and oxygen, suggestions that photosynthesis was occurring on Earth’s surface. Now, astronomers have repeated the experiment, this time with an asteroid-bound spacecraft that swung around Earth in late 2017.

It also found Earth to be teeming with life, reports Katherine Kornei in today's Science, but with an unsettling corollary: Atmospheric levels of carbon dioxide and methane were far higher than they were during the Galileo flyby.

 

“It’s a challenging intellectual enterprise,” says Dante Lauretta, a planetary scientist at the University of Arizona in Tucson and principal investigator of NASA’s Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) mission. “I really tried to channel Carl Sagan.”

The main goal of OSIRIS-REx is to return samples from Bennu, an asteroid as big as the Empire State Building. But during the Earth flyby—which brought the spacecraft 22 times closer to our planet than the moon—scientists pointed its instruments toward home.

The team spotted hurricanes Maria and Jose, and its spectrographs—used to detect gases based on the absorption of specific wavelengths of light passing through the atmosphere—recorded levels of methane, oxygen, and ozone far higher than values expected from a lifeless world. That implies that biological processes were creating these compounds, the team reported last week at the Lunar and Planetary Science Conference in The Woodlands, Texas. The researchers also found that visible light was being absorbed by Earth’s landmasses, a clear sign of photosynthesis.

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