Nasa spokesman Don Savage said they were not clear about what caused the Mars Polar Lander to disappear as it approached the Martian surface and rejected the earlier claims of a cover-up.
If a large body of water once existed on the red planet, the remainder of the water must now either be stored below the surface and in the much smaller south polar cap, or have been lost to space.
"While our results are still very new, our thinking is that the mercury detected by Lamp from the Grail site might be related to an enhancement at the poles caused by mercury atoms generally hopping across the surface and eventually migrating toward the cold polar regions, " said Kurt Retherford, the chief scientist for Lamp.
Kearns and a team of scientists led by Alan Strong of NOAA's National Environmental Satellite, Data and Information Service analyzed sea surface temperature data from the agency's polar-orbiting satellites from 1984 through 1996.