CU听Boulder Professor Larry Esposito has been eying the fabulous rings of Saturn for much of his career, beginning as a team scientist on NASA鈥檚 Pioneer 11 mission when he discovered the planet鈥檚 faint F ring in 1979.
He followed that up with observations of Jupiter鈥檚 and Saturn鈥檚 rings from the Voyager and Galileo spacecraft, which carried instruments designed and built at CU Boulder. Now, as the principal investigator on CU Boulder鈥檚 $12 million Ultraviolet Imaging Spectrograph (UVIS) on the Cassini-Huygens mission to Saturn, Esposito and his Cassini colleagues are feeling a bit somber: The spacecraft has run out of fuel and will disintegrate in Saturn鈥檚 dense atmosphere early on the morning of Sept. 15.
鈥淲e are still making discoveries about the Saturn system studying the Cassini data, and we expect to be making them for some time,鈥� said Esposito of CU Boulder鈥檚 . 鈥淏ut Sept. 15听will be a bittersweet ending to a mission that has fascinated us as scientists and enthralled the public with images and new findings for many years.鈥�
Discoveries galore
The UVIS instrument suite, a set of telescopes used to measure ultraviolet light from the Saturn system, has been used to study the structure and evolution of Saturn's rings; the chemistry, clouds and energy balance of Saturn and Titan; and the surfaces and atmospheres of some of Saturn's 62 known moons, said Esposito.
Launched in 1997 and pulling up at Saturn in 2004 for the first of hundreds of orbits through the planet鈥檚 system, the mission has fostered scores of dazzling discoveries. These include in-depth studies that date and even weigh the astonishing rings,听the discovery of methane lakes on the icy moon Titan,听water plumes found squirting from the moon Enceladus听and close-up views of the bright auroras at the planet's poles.
One of Esposito鈥檚 favorite discoveries using UVIS was the detection of a huge cloud of neutral oxygen atoms in the Saturn system on approach in 2003, which puzzled scientists for years. Subsequent research by the Cassini team indicated the oxygen atoms were coming from a salty, subterranean ocean on Enceladus, which scientists think may have conditions favorable for primitive life.
How old are Saturn鈥檚 rings?
Many discoveries by Esposito and his UVIS team involve Saturn鈥檚 rings鈥攎ade up of ice, rocks and moonlets as large as Mount Everest鈥攖he age of which have been debated for decades. Esposito, who used observations from the Voyager mission to compare the rings of Saturn, Jupiter and Neptune, believes Saturn鈥檚 rings may be as old as the solar system, which is believed to have formed some 4.6 billion years ago.
鈥淲hen the two Voyager spacecraft passed by Saturn in 1980 and 1981, we thought the rings were relatively young,鈥� Esposito said. 鈥淏ut data from Cassini are consistent with the picture that Saturn has had rings throughout its history.
鈥淲e see extensive, rapid recycling of ring material in which moons are continually shattered into ring particles, which then gather and reform moons.鈥�
Other UVIS team members from CU Boulder include Ian Stewart, George Lawrence, William McClintock, Alain Jouchoux, Greg Holsclaw, Emilie Royer, Anya Portyankina and Michael Aye.
Esposito likened the ever-changing rings at Saturn to construction in Beijing, China, where marble from structures erected during the Ming Dynasty (1368鈥�1644) is being recycled to build new structures today.
鈥淭he same sort of thing is happening with Saturn鈥檚 rings,鈥� Esposito said. 鈥淭hey are renewed continually, so the rings themselves can be ancient, but the structures we see today are just part of their current manifestation. We have even watched the rings changing over the course of this mission.鈥�
Cassini鈥檚 grand finale
The UVIS instrument will be turned on during Cassini鈥檚 final dive into Saturn鈥檚 atmosphere and will be routing data to Earth until the mission is over, said Esposito, one of many mission scientists who are gathered at NASA鈥檚 Jet Propulsion Laboratory (JPL) in Pasadena, California, for Cassini鈥檚 grand finale.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of Caltech, manages the mission for NASA's Science Mission Directorate, Washington. JPL designed, developed and assembled the Cassini orbiter.
CU Boulder is the only university in the world to have designed and built instruments that have visited every planet in the solar system, plus Pluto. LASP students control four NASA satellites from campus, and about 120 undergraduate and graduate students working are there on different aspects of flight projects, ranging from engineering and spacecraft operations to data management and science analysis.听
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