NASA’s Cassini spacecraft completed the first of three final flybys of Saturn’s icy moon, Enceladus. On October 14, Cassini passed within 1,838 kilometers (1,142 miles) of Enceladus, providing unprecedented views of the moon’s north polar region.
This marked Cassini’s 20th close flyby of the icy snowball-like moon since arriving at Saturn over a decade ago. A handful of images were downlinked yesterday in honor of the spacecraft’s 18th launch anniversary, with more to come over the next several days.
Enceladus has intrigued scientists from the very beginning. Thanks to low-resolution images captured by Voyager, scientists had an idea of what the frigid satellite's northern pole looked like, and were eager to see the region in greater detail. Early on in Cassini’s mission, the probe conducted several flybys of the moon’s north pole, but could never get a good look as the region was blanketed in wintry darkness. Now that it’s summer in the region, the area is illuminated and scientists confirmed what they had long suspected: a heavily cratered north pole.
The north pole of Saturn's icy moon Enceladus. NASA/JPL-Caltech/Space Science Institute
What they didn't expect to find was a contrasting landscape with a surprising series of spidery surface fractures creeping across a battered terrain. "The northern regions are crisscrossed by a spidery network of gossamer-thin cracks that slice through the craters," Cassini imaging team member Paul Helfenstein, from Cornell University in Ithaca, New York, said in a statement. "These thin cracks are ubiquitous on Enceladus, and now we see that they extend across the northern terrains as well."
The region is also littered with craters that appear to be melting into each other. This bizarre landscape prompted many "ooohs" and "aaahs" from viewers and even comments from scientists on Twitter such as "Enceladus what are you doing?"
NASA/JPL-Caltech/Space Science Institute
Wednesday's flyby has already produced incredible images, but the best is yet to come. This first flyby is a prelude to Cassini’s most daring Enceladus adventure: flying through the moon's southern icy plumes. On October 28, the probe will fly over the south polar region at a distance of only 49 kilometers (30 miles) above the surface.
In 2005, Cassini first spotted a series of geysers near Enceladus' south pole, spewing water-ice out into space. The powerful jets are fueled by a subsurface ocean. Last month, we learned this ocean covers the entire moon, sloshing around under an icy crust.
According to NASA's statement, as part of the upcoming encounter, "Cassini will make its deepest-ever dive through the moon's plume of icy spray, sampling the chemistry of the extraterrestrial ocean beneath the ice."
Scientists expect to uncover clues about the moon's hydrothermal activity and learn about the ocean's chemistry, both of which relate to Enceladus' habitability. The team will also analyze data to look for evidence of geological activity in the north polar region.
"We’ve been following a trail of clues on Enceladus for 10 years now,” said Bonnie Buratti, a Cassini science team member and icy moons expert at NASA’s Jet Propulsion Laboratory in Pasadena, California. “The amount of activity on and beneath this moon’s surface has been a huge surprise to us. We’re still trying to figure out what its history has been, and how it came to be this way.”
Cassini’s final approach will occur on December 19, when the probe will analyze how heat is generated within its interior from a distance of 4,999 kilometers (3,106 miles).