New close-ups of Saturn’s icy moon Enceladus taken by the Cassini spacecraft during a November flyby and released by NASA February 23 provide fresh evidence that the moon’s interior may be hospitable to life.
Cassini observed some 30 small jets of water vapor and water ice spewing from the southern hemisphere of Enceladus, about 20 more than previously seen. In addition, the most detailed infrared map of one of the south pole’s fissures, where jets emanate, indicates that the surface temperature there might be as high as 200 kelvins (-73º Celsius), or about 20 kelvins warmer than previously estimated.
Although the temperature estimate is not yet definitive, the hotter the surface temperature, the hotter the moon’s interior, notes Cassini imaging team leader Carolyn Porco of the Space Science Institute in Boulder, Colo. That “strengthens the evidence for liquid water as the source of the jets,” she says, upping the chances that life could be present in at least part of the moon’s interior.
The craft, which has toured Saturn and its moons since 2004, came within 1,600 kilometers of Enceladus’ surface during the flyby. Cassini has swooped closer to the moon in the past, but this pass provided one of the most detailed infrared portraits of the fissures, dubbed tiger stripes. The temperature of one stripe, known as Baghdad Sulcus, exceeds 180 kelvins and may be as high as 200 kelvins, says John Spencer, a member of Cassini’s composite infrared spectrometer team at the Southwest Research Institute in Boulder, Colo.
By overlaying the infrared map with visible-light images of the moon’s southern hemisphere, researchers have seen more clearly than ever before that the fissures are the source of the jets, says Cassini project scientist Bob Pappalardo of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. In revealing that there are many more jets than previously known coming together to form vast plumes of ice and water vapor, the new images may provide additional clues about how and why the moon generates such spouts in the first place, Pappalardo says.
The November 21 flyby, Cassini’s eighth targeted flyby of Enceladus, was the last look with the craft’s visible-light camera. The region now plunges into 15 years of darkness.