No mention of CO2 outgassing or liquid CO2 flows by this scientist:

Elevations of water-worn features on Mars: Implications for
circulation of groundwater

Michael H. Carr
U. S. Geological Survey, Menlo Park, California, USA
Received 16 January 2002; revised 10 April 2002; accepted 5 June 2002; published 17 December 2002.

Central to the model of the evolution of the martian hydrosphere by Clifford and
Parker [2001] is a permanent freezing of the planet at the end of the Noachian and
recharge of the global groundwater system by basal melting of ice-rich polar deposits.
Acquisition of MOLA data by Mars Global Surveyor provides a means of testing the
model, since discharge of water onto the surface, after development of the cryosphere, is
driven by the hydrostatic head created by the difference in elevation between the base of
the polar-layered terrain and the discharge site. The new data show that, while most post-
Noachian water-worn features are at a lower elevation than the base of the polar-layered
terrains, as required by the model, there are exceptions. Prominent among these are
possible lacustrine deposits within the canyons, tributaries to the canyons, and valleys on
several volcanoes. These high-standing features can be reconciled with the model if
volcanic melting of ice within the cryosphere is invoked as a source for water at high
elevations. An alternative is that high pressures may have developed below the cryosphere
as a result of water being trapped beneath the growing cryosphere and the impermeable
basement. Yet another alternative is that, since the end of the Noachian, the groundwater
system has been recharged by precipitation during occasional warm periods.

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 107, NO. E12, 5131, doi:10.1029/2002JE001845, 2002