Saturn’s ocean-covered moon Enceladus constantly spews water into space through fractures in its icy crust. The spacecraft Cassini determined the composition of these jets in the mid-2000s and found molecules that included carbon dioxide and ammonia, both crucial for life on Earth. And now, in a study published on Thursday in Nature Astronomy, scientists have reanalyzed the Cassini samples and revealed Enceladus’s great chemical diversity—making this small icy moon the top candidate for finding alien life in our own solar system.

The study’s lead author, Harvard University biophysicist Jonah Peter, was intrigued by previous findings that Enceladus was likely rich in organic compounds, most of which had not been identified. To figure out the moon’s true chemical makeup, Peter and his colleagues at NASA’s Jet Propulsion Laboratory reexamined data collected in 2011 and 2012 by the agency’s Cassini-Huygens mission, which flew a spacecraft through Enceladus’s spectacular water plumes multiple times. Cassini’s samples, analyzed by the spacecraft’s onboard mass spectrometer (an instrument that identifies compounds by their molecular weight), had initially revealed five types of molecules in the jets: water, carbon dioxide, methane, ammonia and molecular hydrogen.

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