Are the northern plains of Mars a frozen ocean?

P. Janhunen

Geophysical Research, Finnish Meteorological Institute, Helsinki, Finland

Received 27 February 2001; revised 13 November 2001; accepted 7 June 2002; published 13 November 2002.

In this brief report we consider the possibility that the northern plains of Mars would
today be a frozen ocean, covered by a rather thin (at most of the order of a few hundred
meters) layer of volcanic and impact debris and dust that prevents the ice beneath from
being directly observed and thermally protects it from summertime sublimation (according
to current models, subsurface ice in the high latitudes is stable under current climatic
conditions). The frozen ocean hypothesis would naturally explain the striking topographic
flatness of the northern plains. We show that the frozen ocean is plausible in terms of
current models of paleoclimatic development.We also discuss the possibility that a remnant
salty brine ocean could still exist under the ice and that electric currents flowing in it would
be responsible for the recently observed 40 nT Northern Hemisphere magnetic
anomalies. The latter hypothesis could be tested by suitably placed surface
magnetometers.

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 107, NO. E11, 5103, doi:10.1029/2000JE001478, 2002