Las Vegas Review-Journal (Sunday)
Get rings, then retire
Saturn farewell tour to usher out Cassini
CAPE CANAVERAL, Fla. — NASA’s Cassini spacecraft faces one last perilous adventure around Saturn.
Cassini swings past Saturn’s mega moon Titan this weekend for a gravity-assisted, orbit-tweaking nudge.
“That last kiss goodbye,” as project manager Earl Maize calls it, will push Cassini onto a path no spacecraft has gone before: into the gap between Saturn and its rings. It’s treacherous territory. A particle from the rings — even as small as a speck of sand — could cripple Cassini, given its velocity.
Cassini will make its first pass through the relatively narrow gap Wednesday. Twenty-two crossings are planned, about one a week, until September, when Cassini goes in and never comes out, vaporizing in Saturn’s atmosphere.
Launched in 1997, Cassini reached Saturn in 2004 and has been exploring it from orbit ever since. Its European traveling companion, Huygens, landed on Titan in 2005. Cassini’s fuel tank is practically empty, so with little left to lose, NASA has opted for a risky but science-rich grand finale.
“What a spectacular end to a spectacular mission,” said Jim Green, NASA’s planetary science division director. “I feel a little sad in many ways that Cassini’s discoveries will end. But I’m also quite optimistic that we’re going to discover some new and really exciting science as we probe the region we’ve never probed before.”
There’s no turning back once Cassini flies past Titan, Maize said.
This last leg of Cassini’s 20-year, $3.27 billion voyage should allow scientists to measure the mass of the multiple rings — shedding light on how old they are and how they formed — and also to determine the composition of the countless ring particles. First spotted by Galileo in 1610, the rings are believed to be 99 percent ice; the remaining 1 percent is a mystery, said project scientist Linda Spilker. A cosmic dust analyzer on Cassini will scoop up ring particles and analyze them.
Cassini will have the best views ever of Saturn’s poles. Near mission’s end, Spilker said, “we’re actually going to dip our toe” into Saturn’s atmosphere, sending back measurements until the last possible moment.
All this is on top of a science mission that already has rewritten the textbooks on the Saturnian system.
“But the best is still yet to come — perhaps,” Maize said at a news conference in early April. “But we are certainly going to provide more excitement.”