Two of Saturn’s most intriguing moons, Enceladus and Tethys, have posed for a gorgeous family photograph taken by NASA's Cassini spacecraft. Cassini, which recently performed a dramatic flyby through the plumes of Enceladus, captured the two celestial objects as they lined up in a cosmic bull’s-eye.
Conveniently, as the two moons were only 483,000 kilometers (300,000 miles) apart, this photograph approximately shows their differences in size. Enceladus, the smaller moon in front, was 2.1 million kilometers (1.3 million miles) from Cassini when it was captured on the spacecraft’s specialized, narrow-angle camera.
Enceladus, an icy world 504 kilometers (313 miles) in diameter, features two notable physical characteristics: a global, subterranean ocean, and a region of intense ice volcano-like activity near the south pole. As with the Jovian moon of Europa, Enceladus’ “warm” underground ocean makes it a potentially habitable environment.
Cassini recently flew through one of the plumes given off by the polar ice volcanoes, which technically are more like geysers than the bonafide ice volcanoes found on Pluto. The probe hoped to find compounds in the plumes that were indicative of biological activity beneath the surface; the results are yet to be published.
Tethys, larger than Enceladus at 1,066 kilometers (662 miles) in diameter, gets far less attention from the scientific community, despite showing potential – but still unconfirmed – evidence of icy volcanism. It does have one particularly prominent feature, however: a massive crater 2,000 kilometers (1,243 miles) long. Rather wonderfully, some have noted that it resembles the Death Star from the original "Star Wars" trilogy, with its appearance mimicking that of Saturn's moon of Mimas.