Ice Diary 10
4 January, 2003
I'm Jamie Pierce, one of two mountaineers hired by Case Western Reserve University to ensure group safety for this expedition. My job is a combination of guide, radio operator, weatherman, mechanic, medic, and meteorite hunter.
|Unknown peak near Lewis Cliffs on mountain slope, Antarctica
On days like this, I find reassurance and comfort in my tent and stove. Katabatic winds started to swirl on the not-so-distant horizon, pinning us in for the day. Days typically begin early for me. I check in with McMurdo before anyone else has even opened their eyes: a painful procedure at times, particularly this morning when it was only 20 degrees F in the tent. After our check-in, stoves are lit and the day begins. I work alongside Nancy Chabot, the science lead, and together we determine what we're doing that day.
I lead our group anytime we leave camp. Since we are surrounded by glaciers, I look for stress fractures in the ice that might create crevasses. It's my job to keep us out of these nasty "slots," as I refer to them. I look for any major changes in the surface of the snow and try to gauge where they might be. I look out for the team as well, although by this point everyone is adept at looking for things like the signs of frostbite, etc.
In any given day I fill many shoes, but my main job at this time of year seems to be snowmobile maintenance. They require constant care. Imagine working on a snowmobile in 0 degree F temps I try to get it done a.s.a.p.
It's getting to be that time of year when I start thinking about our exit out of here, and ultimately traversing onto the Beardmore Glacier. In about six days we will get our first Twin-Otter to start taking out Retro (fancy word for garbage) and other non-essential items. We'll be sending out around 1,000 pounds of gear, reducing the loads we have to pull to hopefully half of what we brought in. I think the group will be happier pulling one sled versus the two we pulled when we came in.
5 January, 2003
Metal Detecting in Antarctica
Post by Dante Lauretta
This season we used a metal detector to help in the moraine searches. Professional meteorite hunters around the world use metal detectors, but a metal detector had not been used on an ANSMET expedition since the mid-1980s. There have been many improvements in metal detector technology since then, the most important of which is the ability to "ground balance," or cancel out the dominant background rock.
It is important to remember that only certain types of meteorites can be found with a metal detector. In particular, the ordinary chondrites, certain carbonaceous chondrites, and iron meteorites can be detected. Other carbonaceous chondrites, achondrites, lunar meteorites, and Martian meteorites do not contain enough iron metal to produce a response. Thus, there is an inherent bias in the meteorites that one can find with a metal detector.
Even for the meteorite types that can be detected, it is not as easy to find them as some people think. The metal detector produces a constant hum, not unlike that of a small fly in your ear. The pitch and volume of this hum increases when a metallic object is under the detector's coil. Because of the wide variety of rock types in the moraines, the ground balancing can only cancel out some of the rocks. Other mineralized rocks, known in the metal-detecting world as "hot rocks," still produce a signal on the metal detector. Thus, metal detecting requires a lot of concentration. You have to listen to the audible signal of the detector, examine every rock that produces a signal to determine if it is a meteorite or a hot rock, and keep your eyes open for any interesting meteorites that the metal detector cannot find. On the other hand, metal detecting in Antarctica is much easier than in most other places in the world for one reason: there is no trash!
The metal detector has been used in every moraine that we searched this season, with varying degrees of success. On one day we hit a large concentration of ordinary chondrites and found 20 meteorites in the span of four hours. On other occasions the metal detector had been used all day only to find one or two meteorites. Some areas are loaded with so many different types of hot rocks that it becomes impossible to find the meteorites among them. We also covered ground that contained many meteorites that, for one reason or another, did not produce a response on the detector. These meteorites were only found by painstakingly searching every square inch of the moraine on foot. In some areas we had to get down on our hands and knees to find tiny meteorites hidden among the other rocks.
The wind didn't abate much this afternoon but most of us had developed enough "tent fever" to be willing to work for a few hours. We searched the nearby "That" Moraine and a small ice patch between the moraine and the large ice sheet called Lower MacAlpine Hills. We ended the day with seven new meteorites, bringing the grand total to 444.
6 January, 2003
I thought I had felt the wind blow in Antarctica. Boy, was I mistaken. The Katabatic winds are pummeling our camp with 40-knot gusts and temperatures well below 0F. Jamie and I figured the wind-chill to be -69F. The horizon is fuzzy with suspended snow, although it doesn't seem to be drifting too badly in camp. It is hard to stand up against this wind, and even the most menial chores, like chipping ice or filling camp stoves, can be challenging. The tents have a huge temperature gradient from top to bottom. While my body is comfortable, my feet get cold. Luckily it's nothing a couple of toe warmers can't handle. When people ask after we return if it was cold, today will be the day we think about.
|Metal detector method of meteor searching, Antarctica
We are taking a tent day, of course. I woke up one-half hour late this morning, checked the temperature inside the tent (+16F), and crawled right back into my sleeping bag. I didn't even have to ask Jamie if we were staying in today.
Having a day like today gives me the opportunity to study up on Antarctica. I often find myself looking at the local geology when I'm supposed to be looking for meteorites. For a continent mostly covered by ice, a great variety of rocks can be found here.
When we hiked up a small peak near camp the other day, we stumbled across an outcrop of sandstone belonging to the Buckley Formation. This sandstone was formed during the Permian time period about 320 million years ago. What caught our eyes were the numerous inclusions of petrified wood that looked as if they were only a few years old!
During the Permian, Antarctica was part of a supercontinent called Gondwanaland, and was situated further north than it is today. It probably had a tropical climate and the sandstone we saw was most likely formed as part of a river delta. John Schutt has found entire tree stumps, perfectly petrified in a moraine not far from here. One of them is on display at the Crary lab at McMurdo.
Overlying the Buckley, and dominating the landscape are mountains made of the chocolate-brown Ferrar dolerite. This dolerite is an intrusive igneous rock formed about the time Antarctica was separating from the Gondwanaland supercontinent. Some fragments of the dolerite contain zeolites: small, light-colored crystals that form in gas pockets after the magma has cooled.
Fossils also are found in this region of Antarctica. A dinosaur fossil of an entirely new species was found nearby on Mount Kirkpatrick. But more significantly, fossils of a plant called "Glossopteris" are found in clays all over this region. This is significant, because the same fossils are found in South America and Africa today, strongly suggesting that the three continents were once connected.
9 January, 2003
This morning the wind was calm, the skies clear, and Jamie had good news for us. He said it might be possible for us to get pulled out two days early. This will give us a couple of extra days at McMurdo to get our final chores done. Of course, this is all dependent on the weather.
Under the morning's ideal weather conditions, we set off for the Mouthy Ice. We hoped to find at least 40 meteorites so that we could break the 500-meteorite barrier for this season. On our best day to date, we found 46, so we would be pushing our luck. But we got off to a good start, and although the skies became overcast and the air cooled, we still found 30 meteorites by lunchtime.
Then our hunt exploded! Instead of finding one in a spot, we would find five. All three meteorite collection kits were in constant use. Two of the kits ran out of the freezer tape that we use to seal the sample bags. Most of the meteorites were small (~1cm x 1cm x 1cm), but Scott gets the award for finding the largest. It must have weighed over 10 pounds! He also gets the award for the smallest. It's easy to get picky and pass up the small ones, but you never know what treasures they hold. About 1:00 p.m., I found the 500th meteorite, but it would not be the last.
Thinking that today would be our last day to search, we worked for 10 hours, with a short break for lunch. The wind got colder, but more and more meteorites kept turning up. By 7:00 p.m., we had found 113 meteorites. Even though we could see more meteorites, we decided to stop for the day. We are at 573 for the season, and Dante is leading the chant, "600." I'm so sore tonight from maneuvering the ski-doo and crouching down on the ice to collect each one that I'll be happy no matter how many we recover tomorrow.
Since 1976, the Antarctic Search for Meteorites program (ANSMET), funded by the Office of Polar Programs of the National Science Foundation, has recovered more than 10,000 specimens from meteorite stranding surfaces along the Transantarctic Mountains. Dr. Ralph Harvey and John Schutt are members of each field party, serving as ANSMET continues to be one of the few Antarctic research projects that invites graduate students and senior researchers from other institutions to participate in our field work on a volunteer basis--including the Teacher Experiencing Antarctica (TEA) program. As a multi-agency collaboration, the NSF supports field operations, NASA supports storage curation, distribution and notification of recovered samples, and the Smithsonian provides long term curation facilities for the collection and assist in sample characterization.
In this multi-part Ice Diary series, all commentary is attributed to Andy Caldwell unless otherwise noted, and reprinted by permission as part of his participation in the TEA program.
Related Web Pages
Ice Diary I: Shooting Stars on Ice
Ice Diary 2: Great Scott, A Ghost
Ice Diary 3: Cheer for Team Meteorite
Ice Diary 4: The Hunt Begins
Ice Diary 5: MacAlpine Hills or Bust
Ice Diary 6: Contacting The Mother Pod
Ice Diary 7: Summer Christmas
Ice Diary 8: Where No One Has Gone Before
Antarctic Search for Meteorites (ANSMET)
Planetary Materials Curation (NASA/JSC)
Mars Meteorite Compendium (NASA/JSC)
AMLAMP: Antarctic Meteorite Location and Mapping Program (database of where meteorites have been found)
National Science Foundation (NSF) Office of Polar Programs
McMurdo Long Term Ecological Research (LTER) project
Ice Cube of Exotic Microbes
Antarctic Microbes Colonize under Mars-like Conditions
Meteorite Repository (JSC) Rock Descriptions
NIPR Meteorite Collection (Japan)