EVA-2:

Due to very high winds today, the EVA was restricted to this morning only. Brent and I chose an area from an aerial photograph of this region based on what looked both interesting and accessible - a scenario likely in exploring Mars. With Bill we took the ATV's for a base line study (i.e. without the suits on) towards two buttes to the east. We left the ATV's at the top of a small slope and climbed down to the base of one of the buttes. This one was nicknamed "Wedding Cake" due to its two-tiered morphology. Of course, climbing down to this was much easier without the suits on!

Wedding Cake buttes two tiers look to have the same progression of units from the ground. The lower one-third to three-quarters is a whitish, more resistant unit above which are much less resistant beds which look very fissile, fine-grained and breakable. The less resistant beds are red, brown, dark gray in color. The upper unit also looks to be mostly the resistant whiter unit followed by the reddish beds.

The lower, white units are similar to many seen in Candor Chasma. The unit varies both vertically and laterally in grain size, sorting and composition of larger clasts. Cross-bedding and lenticular shapes are distinguishable, usually due to differing grain-size. Some lenses are normally graded: varying from a fine conglomerate at the bottom up to a better sorted, sandstone. Conglomeratic areas can contain clasts of 3-4 cm easily, and the clasts tend to be sub-rounded.

Within the lower unit we also find lenses or discontinuous layers of a more resistant fine sandstone.

The upper beds of the lower tier and all of the upper tier are inaccessible.

As in Candor Chasma, the presence of conglomerate and sedimentary structures implies that these beds were deposited in water as opposed to a desert environment and the variations in the grain-sizes are attributable to the energy in which they were deposited. In general, the depositional environment appears to have been river channels, to tidal regions and shallow seas (possibly).

This EVA was extremely valuable for comparison with the EVA's wearing a spacesuit! Without the suits mobility is much better, and it is possible to climb over boulders at knee high or greater - this is impossible in the suits! However, from my point of view the most difficult aspect is trying to get a good look at the rocks up close to see the grain etc. and it cannot be done with a helmet on. This means that whilst wearing a suit, more samples are going to have to be collected to analyze on return to the Hab, where a helmet is not necessary. You also notice how much you use "touch" as a method for analyzing and diagnosing rocks in the field when you have gloves on and cannot use this sense. Also, see Brents summary for April 1st on the difficulties of opening sample bags with gloves on!!!