NASA's Cassini spacecraft swung by three Saturn moons in cosmic triple play and beamed new photos of the satellites home to Earth.
The newly released photos from the flyby reveal the surfaces of Dione, Enceladus and Tethys in intriguing detail. The images, taken between Aug.13-14, are still in their raw form and have yet to be processed by Cassini mission scientists, yet still reveal the terrain of three very different Saturn moons. [New photo of Saturn's moon Enceladus.]
One snapshot of Dione, taken Aug. 13 from 74,000 miles (119,000 km) away, shows the many craters pocking the moon's water-ice surface. Dione is about 700 miles (1,120 km) in diameter, and it orbits at 234,000 miles (377,000 km) from Saturn—about the same distance as our own moon is from Earth.
Tethys shares many characteristics with Dione; it's nearly the same size – 662 miles (1,066 km) across and is composed mostly of water ice. And like Dione, Tethys boasts a rugged, crater-laden beauty, which the Cassini spacecraft captured in another photo.
Cassini was about 24,000 miles (38,000 km) from the surface of Tethys when it photographed Penelope crater, which at 90 miles (150 km) wide is the moon's second-largest crater.
Enceladus, however, is a different beast than Dione and Tethys entirely.
While also covered in water ice, Enceladus is only about 313 miles (505 km) across, and it appears to be more geologically active than the other two satellites. Previous Cassini flybys have spotted great geyser-like plumes of water vapor and organic particles venting from long fissures in Enceladus' surface.
On this most recent flyby Cassini was checking these fissures, which scientists have dubbed "tiger stripes," in Enceladus' southern polar region. Some of Cassini's pictures were taken with an infrared camera, which mission scientists plan to analyze to create temperature maps of the fissures.
In one set of observations, the Enceladus fissure Damascus Sulcus stands out clear in visible and infrared views, Cassini mission managers said in a statement.
"Scientists are still analyzing the results," they added.Other visible light photos don't highlight the fissures, but they do yield a good look at Enceladus, which may have a liquid interior, researchers have said. In one view, a shadowy Enceladus appears to hover over the bright limb of Saturn.
The Enceladus snapshots were taken from a range of 24,000 miles and 36,500 miles (39,000-59,000 km).
The Cassini probe launched in 1997 and arrived at Saturn in 2004. Cassini also dropped the Huygens probe onto the surface of Titan, the largest of Saturn's more than 60 known moons and a body that some scientists think might be capable of supporting Earth-like life.
Cassini has swooped by Titan several times before, most recently in June. The cloud-covered moon is the target of the probe's next photo-op flyby, scheduled for Sept. 24.
The Cassini-Huygens mission is a joint effort of NASA, the European Space Agency and the Italian Space Agency. Though initially slated to be decommissioned next month, its activities have been extended through 2017.
- Gallery — The Rings and Moons of Saturn
- Cassini's Greatest Hits: Photos of Saturn
- Saturn's Aurora Heartbeat Discovered