Cassini prepped to conduct ‘screaming’ pass through Enceladus’ plume
Scientists and engineers at NASA’s Jet Propulsion Laboratory are preparing the Cassini spacecraft to conduct a daring run through a plume ejected from the surface of Saturn’s moon Enceladus. That pass, which will see the spacecraft reach speeds of 19,000 mph (30,578 km/h), will help to better understand the dynamics involved with the ocean on this distant, icy world.
On Wednesday, October 28, 2015, Cassini will “sample” the water ejecting up from geysers spraying up from Enceladus. At around 15:20 SCET/UTC, at an altitude of approximately 49 km (30 miles) above the moon’s south polar region, Cassini will soar through the plume – which has the same consistency as smoke – and, in so doing, conduct the long-lived vehicle’s deepest dive through one of Enceladus’ plumes.
The Cassini scientists anticipate that this dramatic maneuver will provide them with more information about the ocean that resides below the moon’s frigid exterior – as well as whether the world might harbor alien life.
The flyby is expected to provide additional information about hydrothermal activity taking place within Enceladus. The scientists speculate that the hot waters below the moon’s icy surface could provide a habitat for simple life forms.
Cassini will use its ion and neutral mass spectrometer instrument (INMS) to detect molecular hydrogen as it flies out into space through the plume.
Traveling through the plume could also help researchers determine if the plume is a single column-based structure or if individual jets and eruptions are its cause.
“There’s really no room for ambiguity,” said Sascha Kempf, a CDA team co-investigator at the University of Colorado. “The data will either match what our models are telling us about the rate at which the plume is producing material or our concept of how the plume works needs additional thought.”
The Cassini scientists expect its cosmic dust analyzer (CDA) to provide them with a better understanding of the actual composition of the plume. The low altitude of this pass should allow the CDA to sample denser molecules – including potential organics. Cassini has made similar passes before – but at far higher altitudes. The CDA can detect up to 10,000 particles per second as it passes through the plume.
Scientists also noted that they expect to be able to estimate just how much material is ejected from the moon’s ocean and out into the space around the giant ringed planet that it orbits.
“Confirmation of molecular hydrogen in the plume would be an independent line of evidence that hydrothermal activity is taking place in the Enceladus ocean, on the seafloor,” said Hunter Waite, INMS team lead at Southwest Research Institute in San Antonio. “The amount of hydrogen would reveal how much hydrothermal activity is going on.”
Imagery will be collected by Cassini’s cameras both before and after the spacecraft’s pass through the plume. These cameras will drag across Enceladus’ south polar region at the point of closest approach. It is anticipated that these images will be the sharpest ever taken of this region, and it should be lit by reflected light from Saturn itself.
The incredible speed of this pass will cause blurring in the images. Scientists speaking during a teleconference held on Monday, Oct. 26, stated that they will work to clear this up before these images are released to the public.
“Cassini truly has been a discovery machine for more than a decade,” said Curt Niebur, Cassini program scientist at NASA Headquarters in Washington. “This incredible plunge through the Enceladus plume is an amazing opportunity for NASA and its international partners on the Cassini mission to ask, ‘Can an icy ocean world host the ingredients for life?'”
Cassini will carry out the last of its three close flybys of Enceladus on December 19, 2015, when it will cruise above the frozen world at an altitude of some 3,106 miles (4,999 kilometers). Wednesday’s pass and the flyby slated to take place in December will help gauge just how much heat is coming from the moon’s interior.
“It’s not going to be our last [flyby] but arguably this one going to be our most dramatic – we are going to be screaming over the south pole at over 19,000 miles per hour, just 30 miles above the surface – and we’re going to go right through the plume,” said Earl Maize, Cassini’s Project Manager with NASA’s Jet Propulsion Laboratory.
While these upcoming flybys might appear to be tight, the closest approach of all took place in October of 2008 when Cassini arced a mere 16 miles (26 kilometers) above Enceladus. Despite this, when Cassini passed through the plume seven years ago, it was at a far higher altitude than what is planned on taking place on Wednesday.
Cassini-Huygens is not just a NASA affair, however. Other partners involved with the spacecraft include ESA (European Space Agency) and the Italian Space Agency. In terms of the U.S. space agency, the Jet Propulsion Laboratory manages Cassini for NASA’s Science Mission Directorate.
Video courtesy of NASA Jet Propulsion Laboratory
Jason Rhian spent several years honing his skills with internships at NASA, the National Space Society and other organizations. He has provided content for outlets such as: Aviation Week & Space Technology, Space.com, The Mars Society and Universe Today.