Oceans on Mars: An assessment of the observational evidence and possible fate
For those who are interested, a reprint of the paper that Linda Martel references in the PSRD piece:
Carr, M. H., and J. W. Head III
Oceans on Mars: An assessment of the observational evidence and possible fate
J. Geophys. Res., 108 (E5), 5042, doi:10.1029/2002JE001963, 2003.
is available as an ~2.1 Mb PDF file.
