In Flyby of Saturn's Moon Rhea, Cassini Probe Gets First Whiff of Non-Earthly Oxygen
Saturn's Moon Rhea NASA NASA's Cassini spacecraft has taken a breath of oxygen while passing over the icy surface of Saturn's second-largest moon, marking the first time a spacecraft has directly sampled oxygen in the atmosphere of another body. Cruising just 60 miles above Rhea, one of more than 60 moons orbiting Saturn, Cassini found an extremely thin atmosphere of oxygen and carbon dioxide likely sustained by high-energy particles slamming into the moon's frozen surface. Rhea's isn't the only other atmosphere in the universe, but it is so thin that Cassini had to fly through it just to confirm that it was there at all (other atmosphere's have been detected and studied from afar by tools like the Hubble Space Telescope). According to Cassini's onboard science instruments, Rhea's atmosphere contains something like 50 billion oxygen molecules per cubic meter, matched by 20 billion carbon dioxide molecules. Rhea and it's larger brother...