Thursday, March 29, 2007
Day 2: Mahana!
"The word for the week is 'adaptability'"
So spake Liza Coe, our illustrious leader.
Adaptability works great, lucky happenstance works better. :)
After a short night's sleep, I woke again, before dawn to have enough time for a shower and some personal grooming before breakfast. Having missed the sign ups last night, I took a look to see what was still left. Following my strategy from yesterday, I chose to try the Photosynthesis group's daily expedition. They were planning to head out over the alkalai flats and make some observations on the growth patterns and diversity of the bacterial and microbial life.
Immediately after breakfast, my plans were changed. Four groups, including the photosynthesis group, were being merged into one big "geologic tour" group. Meh - large groups make for little fun, less "face time" and more of a 'tour group' feeling. I hate tour groups.
Luckily for me, I chose to ride with Linda Powers, a researcher out of the University of Arizona, who was here with one of her graduate students, Heather, and one of her company's engineers, Drew. They were using Dr. Powers' creation, an advanced microbial life detector, as a tool for Heather's research into the diversity of life in different types of desert soils.
On the ride out to the Cima Lava Fields, our first site, Dr Powers described her work on "Mahana", and how Heather's thesis work was using the device. They would be gathering sterile soil samples from the various locations we would be visiting with the group. They had no teachers "assigned" to their team, so I volunteered to help. Since we were more or less sticking with the tour group, I got to have the best of both worlds; the geologic tour with Steve Wells, and the sample gathering experience of field research.
Sterile sample gathering refers to the method by which the sample is gathered, not the soil itself. Since Heather is measuring the quantity of bacteria and other biological material in the soil, any external "riders" would skew her data. We had to be sure to use sterilized instruments to gather the samples, sterile bags to store it, and we had to take extra care to not touch the sterilized surfaces of our tools. Our gathering team would take two samples at each location to ensure the quality of each. The samples were carefully labeled with the location, including the GPS coordinates, and the sample taker's initials. Hopefully, they won't be throwing out the ones labeled "ML" :)
In the meantime, Steve Wells told us all about the formation of "Desert Pavement" and "Desert Varnish". Pavement is an odd phenomenon where the surface of the ground becomes covered with many interlocked small rocks. Under this layer are three more layers. The pavement is actually formed by the windblown or aeolian dust, which trickles down between the rocks, forming the underlaying soil bed. When you scrape away the thin surface layer of loose rocks, you will find the most recently deposited dust. Over time, with the scant rainfall and slight pressure from the overlaying material, the dust compresses into tightly packed "peds", or polygonal pads, a few inches per side. Dr. Wells called the ped layer, "Layer A".
As water flows down the edges of the peds, it carries minerals and small amounts of dust, which fill the gaps in the peds, making them even more tightly packed. The rainwater also supplies bacteria in the peds with required moisture and nutrients. However, since the peds are so tightly packed, bacteria is far more prevalent on the edges and in the junction between Layer "A" and Layer "B".
Layer "B" is an older layer, below the first layers, determined by a slightly different chemical composition. The water infiltration in the A Layer leeches out the carbonates and other soluable minerals. These minerals are deposited in the B layer, and deeper underground. The higher carbonate and mineral content of the B layer distinguishes it, making it noticibly harder, and much more reddish in color.
Desert varnish is a biological phenomenon -- possibly. One of the theories for its formation is that a mineral eating bacteria lives on the surface of rocks. It is not all that well understood, but it appears to take iron and manganese from the rocks, oxidizes it, and forms a dark, shiny coating on certain types of rocks. The varnish only occurs in a very thin surface layer, so anything that scrapes or cracks the rocks also removes the varnish. The other explanation is that the varnish is a naturally occuring condition, caused by weathering. The bacteria seen on the varnish just happens to like the oxidized minerals, and thrives better where those minerals are present. As with many scientific fields, the only way to determine which is the better theory is to study the condition, and accumulate evidence to support or contradict one or the other of the two theories.
On several of the rocks, older civilizations have etched patterns and symbols on the rocks. We saw a couple of sets of these petroglyphs. The one on the left looks awfully like a Masonic symbol...
After we gathered several sets of samples for Heather, we headed back to base to start calibration and data gathering with Mahana. Once again, my little Mac proved itself useful.
The output from Mahana's driver software needed to be imported into Excel and have the average/mean and standard deviations calculated. So, I put my ol' Mac to work with some simple data entry and calculations -- Yes, Dr. Kress, I actually created tables and graphs using Excel!
On the camping front, the winds blew in last night, and my "hotel" is still standing. I'm keeping my fingers crossed that it will still be there at the end of the week!