title: Amalthea's density is less than that of water.
abstract: Radio Doppler data from the Galileo spacecraft's encounter with Amalthea, one of Jupiter's small inner moons, on 5 November 2002 yield a mass of (2.08 +/- 0.15) x 10(18) kilograms. Images of Amalthea from two Voyager spacecraft in 1979 and Galileo imaging between November 1996 and June 1997 yield a volume of (2.43 +/- 0.22) x 10(6) cubic kilometers. The satellite thus has a density of 857 +/- 99 kilograms per cubic meter. We suggest that Amalthea is porous and composed of water ice, as well as rocky material, and thus formed in a cold region of the solar system, possibly not at its present location near Jupiter.
authors.affiliation: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099, USA. john.d.anderson@jpl.nasa.gov
authors.forename: John D
authors.initials: JD
authors.lastname: Anderson
authors.forename: Torrence V
authors.initials: TV
authors.lastname: Johnson
authors.forename: Gerald
authors.initials: G
authors.lastname: Schubert
authors.forename: Sami
authors.initials: S
authors.lastname: Asmar
authors.forename: Robert A
authors.initials: RA
authors.lastname: Jacobson
authors.forename: Douglas
authors.initials: D
authors.lastname: Johnston
authors.forename: Eunice L
authors.initials: EL
authors.lastname: Lau
authors.forename: George
authors.initials: G
authors.lastname: Lewis
authors.forename: William B
authors.initials: WB
authors.lastname: Moore
authors.forename: Anthony
authors.initials: A
authors.lastname: Taylor
authors.forename: Peter C
authors.initials: PC
authors.lastname: Thomas
authors.forename: Gudrun
authors.initials: G
authors.lastname: Weinwurm
mesh_terms: D006112:Gravitation; D007053:Ice; D018538:Jupiter; D011312:Pressure; D018531:Spacecraft; D014867:Water
chemical_list: D007053:Ice; D014867:Water