LJ wrote:
Does anyone have the numbers for the inages in question?

Alex writes:
Here's the caption for the applicable MOC NA image from the paper:

MOC image M08/01962. (Latitude: 26.0°N, Longitude: 189.7° W). Cluster of cones north of the Cerberus plains. The scene is illuminated from the southwest. Note that cones rest on platy-ridged lava, interpretted to be rubbly-pahoehoe. Also note overlapping and dense clustering of cones. The large cone in the upper-left of image appears to exhibit a nested crater.

Also, an airborne image of an Icelandic analog is given with the following caption:

Air photo of rootless cone field in Laki lava flow north of Innryi Eyrar, Iceland. The scene is illuminated from the southeast. Note that the scale of these cones is comparable to those of martian cones. Also note overlapping and dense clustering of cones.

LJ wrote:
What would happen if lava over-flowed areas with liquid or solid CO2 underneath? Could the cones have been formed in this way, rather than water?

Alex writes:
Lanagan et al. state "Both water ice [Carr, 1996] and liquid carbon dioxide clathrates [Hoffman, 2000] have been proposed to exist in reservoirs in the martian subsurface. However, as carbon dioxide at shallow depths in the martian equatorial environment would be quickly lost to the atmosphere, it is more likely water would be the active volatile."

Alex R. Blackwell
University of Hawaii