[meteorite-list] Space Jewel Hunter (Collecting Meteorites In Antarctica)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:16:30 2004
Message-ID: <200308071438.HAA09628_at_zagami.jpl.nasa.gov>

http://www.newscientist.com/opinion/opinterview.jsp;jsessionid=KMCLPIINMPBG?id=ns24071

Space Jewel Hunter
New Scientist Interview
August 7, 2003

It can plunge to -45 °C. The wind chills you to the marrow. Take your gloves
off for more than 10 minutes and you'll probably lose your fingers. That's
the death-or-glory stuff of Antarctic legend. But for Bill Cassidy, the
continent offers a very different allure. It's studded with meteorites,
which means he'd go back tomorrow. And that's at the age of 75, after a
total of 15 gruelling years leading meteorite-hunting expeditions. So what
makes these black jewels so irresistible? Why are they there? And what is
Nomad? Alison George dragged Cassidy away from his other passion, the
adventures of Harry Potter, long enough to ask him

What kept you going in such an inhospitable environment?

When every meteorite that you look at has never been seen by anybody else,
and every one you pick up has the potential to have secrets locked away that
have never been seen in any other rock, you always have the feeling that it
might be the most interesting specimen that has ever been found. But it's
just amazing being in a place where you can pick up a hundred lifetimes'
worth of meteorites in a few days. I am still kind of incredulous.

What can these Antarctic meteorite collections tell us about other planets?

It is certainly much cheaper to go to Antarctica than to go out into space.
While most of the meteorites we find are well-understood stony meteorites
called ordinary chondrites, we do find some extremely rare meteorites too.
The ANSMET programme found one of the first lunar meteorites as well as the
samples which proved that a certain class of rare meteorite was in fact from
Mars. And in 1984, we discovered the Martian meteorite that some people
believe shows evidence of fossilised bacteria.

In the hunt for evidence of life on other planets, are Antarctic meteorites
prized because of where they landed?

Originally we thought: "Oh boy, this is pristine, there is absolutely no
source of contamination at all," but we found out that actually it is not
perfectly pristine. It's a lot better than if a meteorite lands in a cowpat,
say. But there's also atmospheric contamination: for instance, a Swiss
geochemist has found bromine on the surface of meteorites, and this
apparently comes from the ocean. Antarctica is surrounded by the ocean and
some of these chemicals get into the air and circulate over the continent.
But relatively speaking, Antarctic meteorites would be better for searching
for traces of life.

Do you think there is life on other planets?

I try to keep an open mind. Amino acids have been identified in many
meteorites. This does suggest the potential for life elsewhere in space. Is
there life on Mars? I don't think the evidence that has been suggested so
far is completely convincing. Of course, this is part of a larger question:
is there life elsewhere in the universe? We know that life exists in our
solar system, so which would be more probable: that this is the only dust
grain in the universe that has life on it, or are there other dust grains
that also have life on them? My hope is that there is other life and
eventually we might find it. Meanwhile, the Antarctic is a very good place
to start.

So why do meteorites end up concentrated on the Antarctic ice? Surely falls
are as rare there as anywhere else?

Two reasons. Water is the main cause of weathering of rocks, and in general,
meteorites weather very fast because they contain iron, which rusts. So a
meteorite that falls outside of London, say, can turn into part of the soil
in just a hundred years. In Antarctica, meteorites see a lot of water but
it's all frozen, so they can last up to two million years. The second reason
is that any meteorites landing in Antarctica get embedded in the ice. Most
are carried out to sea because that is the fate of the ice sheet, but in
certain places the ice gets jammed up behind a mountain range. If these
spots are windy, the wind wears the ice away, and new ice moves in. Over a
great length of time any meteorite in the ice gets stranded on the surface.
Then it sits there and doesn't weather away.

What was the eureka moment that made you think Antarctica was a deep-freeze
store for meteorites?

In 1973 I went to a talk about meteorites from Antarctica given by a
Japanese chemist called Makoto Shima. I assumed that he was talking about a
meteorite shower, fragments of the same body that broke up and scattered
around. When you find meteorites close together anywhere else on Earth, they
are all from the same source. Suddenly I realised that he was describing
four or five different types of meteorite among nine that had been found
within a small area. The only thing I could think of was: "How did all these
meteorites get concentrated in a small area?" There must be something in
Antarctica that concentrates meteorites, but at the time I couldn't imagine
what it was.

Didn't other people have the same idea?

The Japanese had already decided that the Antarctic was a good place to
collect meteorites, but I hadn't read any of their papers so it was an
original thought for me. Like me, they didn't know why they were there. My
first proposal for a US meteorite collection expedition was rejected. But as
the Japanese programme continued and they found more meteorites. I reported
this, and that's when the National Science Foundation decided to take it
seriously and fund my proposal.

So you finally got to go - paid for! Was going to Antarctica a lifelong
dream?

I've always been interested, but I didn't expect ever to go there. I was
happy that I had a justification for visiting Antarctica to search for
meteorites. As it turns out, I grew attached to the place.

It must have been incredibly cold.

It's kind of overpowering when you first go into the field. We always go to
very windy places, and that makes you chill a lot faster. It is very cold
anyway: the temperature is usually between -10 and -20 °C, which is not a
difficult range of temperatures if you are dressed for it. But then you have
the wind chill factor. The most extreme that I encountered was about -45 °C.

And beautiful?

Breathtaking. Crevasses, for example, can be fantastic to look at, though
you wouldn't want to end up in one! And in some places there are these
things that look like tsunami, which occur when ice flows over mountains
below the surface. It is like a giant swell in the ocean or a wave, and when
the sun shines through the ice, it is a beautiful blue colour. Of course,
there were 24 hours of daylight during our expeditions.

How did you go about meteorite hunting?

We would camp pretty close to where we'd be working. There'd be six to eight
of us, and we travelled to the ice patches on snowmobiles. We'd line up and
slowly criss-cross the ice very methodically until we had covered he whole
area. Sometimes this would take an entire field season or longer. When
someone saw a suspicious-looking rock, they would stop and take a look and
give a signal, then everyone else would have look at it. It could get
boring, especially if the meteorites looked like the other rocks, and there
were plenty of days when we found nothing.

How do you tell the difference between meteorites and those other rocks?

We look for a crust on the surface, called a fusion crust, which is usually
black and smooth. This forms when the meteorite surface melts as it enters
the atmosphere. Some are not black, though, and as luck would have it those
tend to be the rare ones that are most prized. If the surface has been worn
off then you look for rocks that are different from the rest, watching out
for little granules in the fabric of the meteorite called chondrules, or
flecks of metal.

Can it get dangerous?

These areas tend to be crevassed, but we had a crevasse expert with each
field party who travelled in front. It was literally their life on the line.
We did have accidents of course, and they are always regrettable. A woman
field party member broke her leg and another time a man got second-degree
burns in a tent fire. But we didn't lose anyone. That would have been bad.

What was your best moment on the ice?

I guess the best and the worst moments happened during our first field
season. We went by helicopter up to an ice field next to Mount Fleming.
There we found two meteorites within the first 20 minutes. This was an
ecstatic experience, but then we didn't find any more for six weeks, and
those weeks were pretty bad.

Towards the end of the field season, we wangled a trip out to a patch of
blue ice that we had seen in the distance near the Allan Hills, pretty much
at the limit of allowed helicopter travel. We all went in different
directions and soon we were all jumping up and down signalling to the others
to come and see the meteorite we had found. It turned out that there were no
terrestrial rocks at all - only meteorites. We found 34 in a short space of
time, just lying on the ice. I'd say that was my most memorable experience
in Antarctica. We could claim success, and it set the stage for many
successful field seasons.

What happens to the meteorites that you collect?

They get sent to NASA's Johnson Space Center in Texas, the same place that
handled the rocks collected from the moon. From there they are made
available on a free basis to researchers all over the world.

It's a bit of a sexist question, but what did your wife make of all those
long absences?

I was pretty lucky. When I got married we had discussed the fact that, being
a geologist, I would be away for periods of time doing fieldwork, but I
suspect she never realised it might be that long at a time. My wife has
always been pretty adaptable, and she managed to adjust to the situation. A
lot of people - men and women - probably didn't even bother to try to go to
the Antarctic because they knew it wouldn't work.

Are there other downsides to such fieldwork?

Food! In the field we were eating about 5000 calories a day. That helped
keep us warm and active but when I got back my stomach didn't know that I
was home. I kept craving those calories, and it was a battle to try and
fight those urges.

Sounds like a lot of good reasons for sending robots instead! Haven't you
been involved with developing just such a robot?

Yes. A group from Carnegie-Mellon University in Pittsburgh, Pennsylvania,
did program a robot called Nomad to estimate the probability that a given
rock was a meteorite, based on spectral analysis. It was quite clever, but
not foolproof. We always had it in mind that these methods would be useful
on the moon or on Mars. Unfortunately the developers ran out of money while
it was still pretty basic, so there are no robotic meteorite collectors in
Antarctica. It's a pity because some areas are extremely boring for humans
to search, where only one rock in 5000 is a meteorite. And robots could
extend the field season. Humans work best at the peak of the Antarctic
summer, but robots could work in extreme conditions.

What did you do for fun?

Very often the ice fields we visited would be close to rocky outcrops -
mountain tops poking up through the ice. Around these so-called nunataks
there were usually small hills and valleys in the ice. Sometimes people
would get off their snowmobile and slide down these chutes in the ice and
get a nice little ride. Back home, it's Harry Potter, no contest!
Received on Thu 07 Aug 2003 10:38:49 AM PDT