title: Observations of the north polar region of Mars from the Mars orbiter laser altimeter.
abstract: Elevations from the Mars Orbiter Laser Altimeter (MOLA) have been used to construct a precise topographic map of the martian north polar region. The northern ice cap has a maximum elevation of 3 kilometers above its surroundings but lies within a 5-kilometer-deep hemispheric depression that is contiguous with the area into which most outflow channels emptied. Polar cap topography displays evidence of modification by ablation, flow, and wind and is consistent with a primarily H2O composition. Correlation of topography with images suggests that the cap was more spatially extensive in the past. The cap volume of 1.2 x 10(6) to 1.7 x 10(6) cubic kilometers is about half that of the Greenland ice cap. Clouds observed over the polar cap are likely composed of CO2 that condensed out of the atmosphere during northern hemisphere winter. Many clouds exhibit dynamical structure likely caused by the interaction of propagating wave fronts with surface topography.
authors.affiliation: Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. zuber@tharsis.gsfc.nasa.gov
authors.forename: M T
authors.initials: MT
authors.lastname: Zuber
authors.forename: D E
authors.initials: DE
authors.lastname: Smith
authors.forename: S C
authors.initials: SC
authors.lastname: Solomon
authors.forename: J B
authors.initials: JB
authors.lastname: Abshire
authors.forename: R S
authors.initials: RS
authors.lastname: Afzal
authors.forename: O
authors.initials: O
authors.lastname: Aharonson
authors.forename: K
authors.initials: K
authors.lastname: Fishbaugh
authors.forename: P G
authors.initials: PG
authors.lastname: Ford
authors.forename: H V
authors.initials: HV
authors.lastname: Frey
authors.forename: J B
authors.initials: JB
authors.lastname: Garvin
authors.forename: J W
authors.initials: JW
authors.lastname: Head
authors.forename: A B
authors.initials: AB
authors.lastname: Ivanov
authors.forename: C L
authors.initials: CL
authors.lastname: Johnson
authors.forename: D O
authors.initials: DO
authors.lastname: Muhleman
authors.forename: G A
authors.initials: GA
authors.lastname: Neumann
authors.forename: G H
authors.initials: GH
authors.lastname: Pettengill
authors.forename: R J
authors.initials: RJ
authors.lastname: Phillips
authors.forename: X
authors.initials: X
authors.lastname: Sun
authors.forename: H J
authors.initials: HJ
authors.lastname: Zwally
authors.forename: W B
authors.initials: WB
authors.lastname: Banerdt
authors.forename: T C
authors.initials: TC
authors.lastname: Duxbury
mesh_terms: D002245:Carbon Dioxide; D005118:Extraterrestrial Environment; D007053:Ice; D018535:Mars; D014867:Water
chemical_list: D007053:Ice; D014867:Water; D002245:Carbon Dioxide