archive: SETI [ASTRO] Galileo Spacecraft Finds Thin Atmosphere On Callisto
SETI [ASTRO] Galileo Spacecraft Finds Thin Atmosphere On Callisto
Larry Klaes ( lklaes@bbn.com )
Fri, 05 Feb 1999 13:47:57 -0500
>X-Authentication-Warning: brickbat12.mindspring.com: majordom set sender
to owner-astro using -f
>Date: Thu, 4 Feb 1999 22:10:27 GMT
>From: Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
>To: astro@lists.mindspring.com
>Subject: [ASTRO] Galileo Spacecraft Finds Thin Atmosphere On Callisto
>Sender: owner-astro@brickbat12.mindspring.com
>Reply-To: Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
>
>
>MEDIA RELATIONS OFFICE
>JET PROPULSION LABORATORY
>CALIFORNIA INSTITUTE OF TECHNOLOGY
>NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
>PASADENA, CALIFORNIA 91109. TELEPHONE (818) 354-5011
>
>Contact: Franklin O'Donnell
>
>EMBARGOED FOR RELEASE 1:30 P.M. PACIFIC FEBRUARY 4, 1999
>
>GALILEO SPACECRAFT FINDS THIN ATMOSPHERE ON CALLISTO
>
> NASA's Galileo spacecraft has detected a thin carbon dioxide
>atmosphere on Jupiter's moon Callisto, and has confirmed the
>existence of carbon dioxide on Callisto's surface. The findings
>appear in the February 5 issue of the journal Science.
>
> This latest discovery means that all four of Jupiter's large
>Galilean moons -- Callisto, Europa, Io and Ganymede -- have some
>form of atmosphere.
>
> "Callisto's atmosphere is so tenuous that the carbon dioxide
>particles are literally drifting around without bumping into one
>another," said Dr. Robert Carlson of NASA's Jet Propulsion
>Laboratory, Pasadena, CA, principal investigator for Galileo's
>near-infrared mapping spectrometer instrument. "An atmosphere
>this thin is known as an exosphere."
>
> The instrument detected the carbon dioxide atmosphere during
>observations of Callisto made during the 10th orbit around
>Jupiter in September 1997. Carlson says he and other scientists
>were following up on discoveries made by Galileo upon its arrival
>at Jupiter's system in 1995. The spacecraft detected what
>appeared to be carbon dioxide on Callisto's surface. This latest
>finding confirms that the surface chemical was, in fact, carbon
>dioxide, and that the chemical also appears in the atmosphere
>above Callisto.
>
> "An atmosphere this thin is easily lost due to ultraviolet
>radiation from the Sun, which breaks the molecules into ions and
>electrons which are swept away by Jupiter's magnetic field," said
>Carlson. "For us to find such an atmosphere implies that there
>is a steady flux of carbon dioxide into the atmosphere. Venting
>of gas from the interior is one possibility, and Galileo images
>show surface erosion that suggests carbon dioxide outgassing."
>
> Previous findings indicated that two of Jupiter's moons,
>Europa and Ganymede, have a thin oxygen atmosphere, while Io's
>atmosphere contains sulfur dioxide.
>
> "We're anxious to look for other gases that may be contained
>in Callisto's atmosphere," said Carlson. Scientists will have
>that opportunity when Galileo observes Callisto during two of
>four flybys planned during the remainder of the current extended
>mission. Galileo will make observations of Callisto during
>encounters in May and June; it will be observing other targets
>during flybys of Callisto in August and September.
>
> Those encounters will take place before the two Io flybys
>that will wrap up the spacecraft's extended mission, known as
>Galileo Europa Mission. During the extended mission, Galileo has
>flown by Europa eight times. The spacecraft has been orbiting
>Jupiter and its four largest moons for more than three years.
>
> The Galileo mission is managed by JPL, a division of
>California Institute of Technology, Pasadena, CA.
>
> Additional information and images taken by the Galileo
>spacecraft are available on the Internet at
>http://www.jpl.nasa.gov/galileo . Images are also available at
>http://www.photojournal.jpl.nasa.gov .
>
> #####
>