Cassini Spies Wave Rattling Jet Stream On Planet Jupiter With New Study Released

New movies of Jupiter are the first to catch an invisible wave shaking up one of the giant planet's jet streams, an interaction that also takes place in Earth's atmosphere and influences the weather. The movies, made from images taken by NASA's Cassini spacecraft when it flew by Jupiter in 2000, are part of an in-depth study conducted by a team of scientists and amateur astronomers led by Amy Simon-Miller at NASA's Goddard Space Flight Center in Greenbelt, Md., and published in the April 2012 issue of Icarus.

"THIS IS THE FIRST TIME ANYONE HAS ACTUALLY SEEN DIRECT WAVE MOTION IN ONE OF JUPITER'S JET STREAMS," says Simon-Miller, the paper's lead author. "AND BY COMPARING THIS TYPE OF INTERACTION IN EARTH'S ATMOSPHERE TO WHAT HAPPENS ON A PLANET AS RADICALLY DIFFERENT AS JUPITER, WE CAN LEARN A LOT ABOUT BOTH PLANETS."

Like Earth, Jupiter has several fast-moving jet streams that circle the globe. Earth's strongest and best known jet streams are those near the north and south poles; as these winds blow west to east, they take the scenic route, wandering north and south. What sets these jet streams on their meandering paths-and sometimes makes them blast Florida and other warm places with frigid air-are their encounters with slow-moving waves in Earth's atmosphere, called Rossby waves.

In contrast, Jupiter's jet streams "HAVE ALWAYS APPEARED TO BE STRAIGHT AND NARROW," says co-author John Rogers, who is the Jupiter Section Director of the British Astronomical Association, London, U.K., and one of the amateur astronomers involved in this study.

Rossby waves were identified on Jupiter about 20 years ago, in the northern hemisphere. Even so, the expected meandering winds could not be traced directly, and no evidence of them had been found in the southern hemisphere, which puzzled planetary scientists.

To get a more complete view, the team analyzed images taken by NASA's Voyager spacecraft, NASA's Hubble Space Telescope, and Cassini, as well as a decade's worth of observations made by amateur astronomers and compiled by the JUPOS project.