By Jason WilliamsManaging Editor
A sensor built by researchers at the University of Maryland hasdetected a massive cloud of volcanic gas surrounding Jupiter andextending nearly one astronomical unit into space — which isequivalent to the average distance between the earth and the sun.
The gas is being dispersed as a result of volcanic activity on theJovian moon Io — the most volcanically active body in the solarsystem.
Researchers at the John’s Hopkins University Applied PhysicsLaboratory developed the Charge Energy Mass Spectrometer, which wasplaced on board the Cassini spacecraft. The gas cloud was detectedduring a recent flyby of Jupiter; the sensor picked up the cloud’sionized and nonionized atoms.
The CHEMS sensor measures the composition of ions, and was able toshow that most of the cloud was comprised of sulfur and oxygenparticles, which suggests the presence of sulfur dioxide as well,said Douglas C. Hamilton, a professor of physics at the University ofMaryland and co-author of the report published recently in thejournal Nature.
The likely presence of sulfur dioxide led researchers to Io’svolcanic terrain as the source of the emittance.
“Sulfur dioxide is the chief gas emitted by volcanos, indicatingIo as the likely origin for much of the gas cloud that Cassinidetected,” Hamilton said.
Before stretching into space, the cloud must first break away fromJupiter.
The ions gather speed to escape beyond Jupiter while trapped inthe planet’s magnetosphere, which energizes and ionizes theparticles. However, the ions’ electric charge binds them to theplanet’s magnetic field, so the ions must capitalize on theirenergetic state, which allows them to acquire electrons from otheratoms or molecules and return to a “normal,” or electromagneticallyneutral condition.
This neutrality frees the atoms to drift incredible distances intointerplanetary space — even distances close to 93 million miles.
The route from the mouth of an Io volcano to open space is onemarked by recurring change for the atoms in the gas cloud, whichshift from atoms to ions in the magnetosphere, ions to atoms toescape Jupiter’s magnetic field, and then, for some, back into ionsagain as high-energy ultraviolet photons from the sun bombard theneutral atoms, knocking electrons away.
Ions are atoms that have lost one or more electrons.
The detection is a two-part collaboration on board the Cassinicraft. Atoms are imaged by the Hopkins-developed Ion and NeutralCamera, which provided structural detail of Jupiter’s magnetosphere,detecting atoms in the extensive gas cloud; the CHEMS sensordetermines particle types.
Cassini next moves to Saturn, which it is slated to reach insummer 2004. Saturn is the destination of the Cassini mission, whichwill use the CHEMS and INCA, as well as the Low Energy MagnetosphericMeasurement System to study the space around Saturn and itssatellites.
