Density of Mars' South Polar Layered Deposits
Maria T. Zuber,1*
Roger J. Phillips,2
Jeffrey C. Andrews-Hanna,1
Sami W. Asmar,3
Alexander S. Konopliv,3
Frank G. Lemoine,4
Jeffrey J. Plaut,3
David E. Smith,4
Suzanne E. Smrekar3
Both poles of Mars are hidden beneath caps of layered ice. We calculated the density of the south polar layered deposits by combining the gravity field obtained from initial results of radio tracking of the Mars Reconnaissance Orbiter with existing surface topography from the Mars Orbiter Laser Altimeter on the Mars Global Surveyor spacecraft and basal topography from the Mars Advanced Radar for Subsurface and Ionospheric Sounding on the Mars Express spacecraft. The results indicate a best-fit density of 1220 kilograms per cubic meter, which is consistent with water ice that has 
15% admixed dust. The results demonstrate that the deposits are probably composed of relatively clean water ice and also refine the martian surface-water inventory.
1 Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139–4307, USA.
2 Department of Earth and Planetary Sciences, Washington University, St. Louis, MO 63130, USA.
3 Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91009–8099, USA.
4 Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA.
* To whom correspondence should be addressed. E-mail: zuber{at}mit.edu
