In the ultimate sacrifice for science, the Cassini spacecraft will hurl itself into Saturn’s frigid atmosphere Friday, collecting data until ripped apart by the strain of the dive.
All signals from the craft are expected to cease shortly before 8 am ET. By then, the craft will be tumbling out of control, unable to point its communication antenna in the right direction. It is expected to disintegrate within a few minutes of losing contact with mission controllers.
Despite the unprecedented data the craft will gather in its final moments, its demise will be “emotionally overwhelming,” says Hunter Waite of the Southwest Research Institute in San Antonio, the lead scientist for two of Cassini’s scientific instruments. “I’ve been getting nice little tidbits of scientific discovery handed down to me by Mother Nature for 13 years. … I’ll miss that.”
Hurtling through Saturn’s shroud of hydrogen and helium at nearly 70,000 mph, the spacecraft will glow like a meteor in its last moments -- a fitting finale for a blazing star of the scientific world.
Scientists “understand that it must end,” says Michele Dougherty, professor of space physics at Britain’s Imperial College London and the lead scientist for one of Cassini’s instruments. “But there are a lot of people who don’t really want it to end.”
The craft is out of fuel, and NASA opted to destroy it in Saturn’s churning gases for safety’s sake. If left alone, Cassini might have accidentally sprinkled Earthly microbes on Saturn’s moons, which are now considered some of the solar system’s most likely incubators for life.
The realization that Saturn’s moons are ripe for life is courtesy of Cassini itself. With the spacecraft’s exit, such revelations are less likely. No new missions to Saturn are on the books. “We will go back to Saturn,” Dougherty says. “It probably won’t be in my lifetime.”
In the meantime, scientists can busy themselves with the rich archive of data – more than 600 gigabytes’ worth -- collected by Cassini since its arrival at Saturn in 2004, 6-1/2 years after the NASA craft launched from Cape Canaveral, Fla., carrying the European Huygens probe on its back.
In a brilliant career, Cassini racked up six new named moons orbiting Saturn and captured some of the stuff making up the rings. It revealed that both Titan and Enceladus harbor expansive oceans. And it showed that the ocean on Enceladus is warm and laced with chemicals that could nourish life. Thanks to Casssini, Waite says, researchers know that similar worlds elsewhere in the galaxy are promising places to look for life-friendly conditions.
Not content with the data it has already delivered, Cassini will gather even more as it speeds towards annihilation. Eight of its 12 scientific monitors will be alert during the final plunge, sending observations back to Earth until the communication link is lost.
The craft’s plunge into Saturn was not part of the original plan, but the Cassini team has coaxed the craft’s sensors into cooperating one last time. The reward: information that could be gathered no other way. Dougherty’s team, for example, will collect data on Saturn’s magnetic field. The closer their instrument to the planet, the stronger the magnetic field, and the more likely they’ll notice anything unexpected, she says.
Though exhilarated by the promised gains from what Waite calls “a whole new mission,” the researchers are saddened by the end of a decades-long team effort. “Cassini is all these people that you’ve worked with all these years,” Waite says. “Cassini is much more than an object.”
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