Today (Sept. 15), NASA's Cassini spacecraft will dive into Saturn's atmosphere and disintegrate. You can watch the action live right here on Space.com, starting at 4:00 a.m. PDT (7 a.m. EDT).
The intentional crash is expected to begin at about 4:55 a.m. PDT (7:55 a.m. EDT, 1155 GMT). Scientists at NASA's Jet Propulsion Laboratory (JPL) in California will monitor the descent and collect data from Cassini during the 1 to 2 minutes before the friction and heat from the fall destroy the spacecraft.
NASA's coverage of the event will begin at 4 a.m. PDT (7 a.m. EDT, 1100 GMT), and you can watch it on the Space.com home page, or on our watch-live page, courtesy of NASA. The coverage will include commentary on the end-of-mission activities and an uninterrupted live stream of the JPL mission control center. You can also watch via NASA TV. [Cassini at Saturn in Videos: Latest Mission Events and Amazing Discoveries]
At 6:30 a.m. PDT (9:30 a.m. EDT, 1330 GMT) NASA will host a post-mission news conference from JPL. You can also watch that event live here on Space.com.
"We'll be saddened — there's no doubt about it — at the loss of such an incredible machine," Earl Maize, the Cassini program manager, said during a news conference Wednesday (Sept. 13). "But I think all of us [on the Cassini team] have a great sense of pride … We set out to do something at Saturn, we did it [and] we did it extremely well."
The $3.26 billion Cassini-Huygens mission — a joint effort of NASA, the European Space Agency and the Italian Space Agency — launched toward Saturn in 1997 and arrived at the system in 2004. The Huygens lander separated from Cassini and plopped down on the surface of Saturn's moon Titan shortly after the arrival. The Cassini probe was scheduled to study the Saturn system until 2008, but the mission was given two extensions that stretched its lifetime into 2017.
Now, the probe is nearly out of fuel, and the mission must end. By sending Cassini into Saturn, scientists hope to gather a few bits of in-situ data from the atmosphere of one of the solar system's gas giants. Since April, Cassini has been making a series of loops between Saturn and the planet's innermost rings, "dipping its toe" into Saturn's atmosphere, according to mission scientists.
The crash into Saturn's atmosphere will also ensure that Cassini will not collide with one of the Saturnian moons that researchers think could be habitable. Such a collision could risk contaminating those moons with microbes from Earth.
Cassini's observations of the Saturn system resulted in a long roster of new discoveries, including observations of disturbances and changing features in the planet's rings, and revelations about the potential habitability of some of the system's moons. The spacecraft has taken 453,048 images of the Saturn system during its lifetime, and 3,948 scientific papers have been written based on Cassini data, according to NASA's most recent numbers.
The mission also opened up new mysteries that scientists will now have to investigate without the spacecraft, such as how the planet's magnetic field is generated (the prevailing theory doesn't seem to match up with observations), how quickly the planet's solid core rotates (which should determine the official length of a Saturn day), and how material from the planet's rings mixes with its atmosphere.
"Not only do we have an environment [at Saturn] that is just overwhelming in its abundance of scientific mysteries and puzzles, we got a spacecraft and a team that could exploit it," Maize said. "It's just been an amazing, amazing mission."