[meteorite-list] Ice Diary 10: Frostbitten

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:13:09 2004
Message-ID: <200304241622.JAA08680_at_zagami.jpl.nasa.gov>

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Ice Diary 10: Frostbitten
Astrobiology Magazine
April 24, 2003

Summary: The Ice Diary series explores the adventures of a
dedicated group of meteor hunters. The National Science
Foundation, NASA and the Smithsonian collect and curate
extraterrestrial samples scoured from the South Pole. The diary
entries provide a personal tour of a recent expedition, with all the
immediacy of being there.

Ice Diary 10
Frostbitten

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.

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.

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.
Received on Thu 24 Apr 2003 12:22:30 PM PDT