Cassini to Track Venus Transit, Study Exoplanets


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NASA announced today that it will begin using the Cassini probe's visual and infrared mapping spectrometer (VIMS) for uses other than studying Saturn and its moons.

On Friday, from its vantage point in orbit around Saturn, the VIMS will be used to track Venus as it travels across the face of the sun. A similar Venus transit could be seen from Earth earlier this summer, but Friday's transit will be the first time a spacecraft has tracked the transit of a planet in our solar system from beyond Earth.

The VIMS will collect data on Venus' atmosphere during the event. The observations are also a chance for astronomers to test the VIMS's ability to observe planets outside the solar system, in an effort to reduce the amount of signal noise. The instrument has already been used to observe a transit by an exoplanet called HD 189733b.

"Interest in infrared investigations of extrasolar planets has exploded in the years since Cassini launched, so we had no idea at the time that we'd ask VIMS to learn this new kind of trick," said Phil Nicholson, the VIMS team member based at Cornell University. "But VIMS has worked so well at Saturn so far that we can start thinking about other things it can do."

Since Cassini's launch in 1997, astronomers have used NASA's Hubble and Spitzer space telescopes to identify numerous exoplanets. Scientists are hoping to use Cassini's VIMS to investigate the atmospheres of those planets, in particular whether they contain methane or other hydrocarbons.

The VIMS has also been used in another novel way recently. Back in April 2012, astronomers used the instrument to take thermal data from warm fissures located on Saturn's moon Enceladus.

"For the first time, we were able to see that the jets coming from the surface of Enceladus originated in very small, very hot spots," said Bonnie Buratti, a VIMS scientist at NASA's Jet Propulsion Laboratory. "This new observation is good evidence for liquid water underneath the surface."

(Images courtesy NASA/JPL/University of Arizona)