Brief but beguiling look at Enceladus
Cassini’s sojourn to Saturn’s icy moon may help scientists decide whether it’s habitable.
A NASA spacecraft’s deep dive through the icy geysers of Saturn’s moon Enceladus may provide scientists with some muchneeded information about one of the most mysterious worlds in the solar system.
Cassini’s sojourn last week through the plume of water particles, organic molecules and other chemicals lasted less than a minute, but the data collected by the Jet Propulsion Laboratorybuilt craft may help scientists determine whether — and to what extent — Enceladus is friendly to life.
Before whizzing by the moon at speeds of 19,000 mph, Cassini was reoriented so that its gas- and dust-analyzing instruments would be able to capture as much data as possible. Those measurements should give researchers an even better look at what lies within the icy moon — and whether it’s a habitable environment.
Linda Spilker, Cassini’s project scientist at JPL in La Cañada Flintridge, said researchers want to confirm the presence of molecular hydrogen in the plume, because that would be evidence of hydrothermal activity somewhere beneath Enceladus’ surface. The situation could be akin to the hydrothermal vents on Earth’s ocean floors that host deepwater microbial life.
The more hydrogen Cassini finds, the more hydrothermal activity there must be — which means more available energy for hypothetical Enceladus microbes. Scientists have already detected methane and other organic molecules in the geyser, but this week’s plunge — allowing Cassini to come within 30 miles of the moon’s surface — allowed them to sample a denser part of the plume. This region might contain complex organic molecules that are too heavy to float to places Cassini has visited before.
“We might find new organics that we haven’t seen previously that are just at the limits of our detection,” Spilker said.
The scientists also want to know whether the plumes of gas emanating from four “tiger stripe” slits around the moon’s south pole are shooting out like jets or erupting continuously along the length of each stripe like a “curtain” of material. Solving that mystery could offer insight into how long Enceladus has been active, she added.
Compared to Jupiter’s moon Europa, which also hosts an ocean, Enceladus is tiny, only about 300 miles across. And yet this water world could potentially help answer some profound questions about our place in the universe.
“If [life] arose twice in one solar system, the implications for how probable and how frequent it arises in the universe as a whole are profound,” said Curt Niebur, Cassini’s program scientist at NASA in Washington, D.C.
Cassini doesn’t have the instruments to look for living things, only for signs of a habitable environment. Searching for biosignatures and other hints of life would be up to a future mission.