By Ian Simpson
(Reuters) - U.S. space agency NASA's Cassini spacecraft will end its groundbreaking 13-year mission to Saturn on Friday with a meteor-like plunge into the ringed planet's atmosphere, transmitting data until the final fiery moment.
Cassini, the first spacecraft to orbit Saturn, is expected to lose contact with Earth at 7:55 a.m. EDT (1155 GMT) shortly after it enters the gas giant's crushing atmosphere at about 70,000 miles per hour (113,000 km per hour), the National Aeronautics and Space Administration (NASA) said.
Cassini's final transmissions are expected to include unprecedented data from the atmosphere's upper fringe about 1,190 miles (1,915 km) above Saturn's cloud tops. The data will take 86 minutes to reach NASA antennas in Canberra, Australia.
"Not only do we have an environment that just is overwhelming with an abundance of scientific mysteries and puzzles, but we've had a spacecraft that's been able to exploit it," Earl Maize, Cassini project manager at NASA's Jet Propulsion Laboratory in Pasadena, California, said at a briefing on Wednesday.
Cassini's final dive will end a mission that gave scientists a ringside seat to the sixth planet from the Sun. The craft's discoveries included seasonal changes on Saturn, a hexagon-shaped pattern on the north pole and the moon Titan's resemblance to a primordial Earth.
Cassini also found a global ocean on the moon Enceladus, with ice plumes spouting from its surface. Enceladus has become a promising lead in the search for places where life could exist outside Earth.
The spacecraft has produced 450,000 images and 635 gigabytes of data since it began probing Saturn and its 62 known moons in July 2004. Cassini is a cooperative project between NASA, the European Space Agency and the Italian Space Agency.
Since Cassini is running low on fuel, NASA is crashing it into Saturn to avoid any chance the spacecraft could someday collide with and contaminate Titan, Enceladus or another moon that has the potential for indigenous microbial life.
Cassini started a series of 22 orbital dives in April, using Titan's gravity to slingshot itself into the unexplored area between the planet and its rings. The spacecraft studied Saturn's atmosphere and took measurements to determine the size of the planet's rocky core.
NASA scientists have said Cassini's final photo as it heads into Saturn's atmosphere will likely be of gaps in the rings caused by tiny moons.
(Reporting by Ian Simpson in Washington, Editing by Rosalba O'Brien)