The Antarctic Search for Meteorites (ANSMET)
The Antarctic Search for Meteorites (ANSMET) program has been searching for meteorites in Antarctica for thirty-five field seasons. ANSMET is a supported by grants from the National Science Foundation, Office of Polar Programs and by the Solar System Exploration Division of NASA (National Aeronautics and Space Administration). The current Principal Investigator (PI) for the program is Dr. Ralph P. Harvey of the Department of Earth, Environmental and Planetary Sciences at Case Western Reserve University. The founder of ANSMET and PI until 1991 was Professor William A. Cassidy of the University of Pittsburgh. ANSMET has recovered nearly 20,000 meteorite specimens from the East Antarctic Ice Sheet since 1976.
Last night I talked with Marianne Mader and two other members of this year’s ANSMET team to learn more about their field work. Marianne and I had met back in early December when we both arrived in McMurdo. The ANSMET team left shortly after we completed Happy Camper school. Their eight member field team has been collecting meteorites on the Polar Plateau for the past six weeks. They are what’s called a “systematic team,” which means they search using a certain system. Another team, the “recon” team (recon is short for reconnaissance), is in another area looking for new sites for next year’s systematic team. Here is Marianne!
Marianne studies impact craters on Earth. Impact craters are those craters made when larger meteorites make contact with the Earth’s surface. She works at Western University in London, Ontario, Canada. This is her first trip to Antarctica. Marianne says that she loves field work and being outdoors. One of her teammates, Tom Sharp, is also here in Antarctica for the first time. He says he’s always loved the outdoors and mountains. Tom is a geologist, working at Arizona State University. Check out Tom’s icy mustache in the photo below.
The third team member in our interview was Stan Love. Stan was here collecting meteorites in the 2004-2005 season. He is an astronaut, and I’ll be telling you more about him in the next few days…I don’t want to give too much away now! He works at the Johnson Space Center in Houston, Texas. He is a planetary scientist and studies tiny materials called interplanetary dust. Stan is shown below with one of the meteorites found this season.
The ANSMET team was flown to the Polar Plateau by LC-130 Hercules aircraft. They actually needed two planes because of all the cargo that is necessary to be out in the field collecting meteorites. They had snowmobiles, food, tents, fuel, equipment used in the collection process, crates to put the meteorites in and so much more! Check out their cargo in the photos below.
The team is flown to 85 1/2 degrees south latitude and 179 degrees east longitude, to an area in the Grosvenor Mountains, by Larkman Nunatak. A nunatak is the tip of a mountain, sticking up out of the ice. Most of the mountains are buried in ice, and we’re only seeing the top.
Once everything is unloaded from the ski-equipped Hercules, it’s time to say good-bye. This is the most remote field camp in Antarctica, which means it is the most remote field camp in the world! Once the ANSMET team is dropped off, they are completely self-sufficient. Of course they can be rescued in case of emergency, but the weather might not always cooperate. The photo below shows the Hercules using ATO (remember from my previous blog, this mean “assisted take off” and is sometimes called JATO “jet assisted take off”). ATO provides that extra boost of power needed to take off on a shorter ice runway in the field.
Up and away! It must be a strange feeling to watch that plane fly off…the group is now totally on their own.
After organizing and distributing all of their gear and supplies, each of the eight team members are towing two sleds for a combined total of approximately 2,400 pounds. The combined total of all ANSMET gear is about 25,000 pounds, which includes the weight of the snowmobiles. Here they are, ready to drive to their campsite.
This is Tom’s snowmobile and load; he’s carrying the four 55-gallon fuel drums on one sled; tents and other equipment on the other. His load was one of the heaviest.
A field camp is set up and serves as the home base for daily field operations. The field camp was moved three times during their six week field season. The first move was 6 miles, the second was 25 miles, and the third was 34 miles. Can you imagine packing up the entire camp below and moving it, then setting it up all over again?
Two people slept in each tent. I found it so interesting that the water they used for cooking and drinking came from snow that was tens to hundreds of thousands of years old.
Part way through the field season, a Twin Otter flew to meet the team and resupply their field camp. This Twin Otter was probably a very welcome sight!
The scientists spent six to eight hours a day searching for meteorites. Lunch might be a warm meal back in the tents, or it could be a scene like this…out on the ice. It’s not always this nice though…temperatures can dip to -18 degrees C (-4 degrees F) and when the wind blows it can feel a lot colder than that.
The team searches for meteorites out on the blue ice surrounding the nunatak. You can see the tips of the mountains (the nunatak) with the blue ice surrounding them…check this out in the photo below.
Out on the blue ice, the wind ablates (wears away) the ice. The blue color is light coming through the ice. It is easier to see meteorites on the snow and blue ice. So WHY are scientists searching for meteorites and what does this process look like?
Geologist study rocks as a record of the Earth. Meteorites are the rock record of the solar system. They are part of the record of the formation of planets, and give clues to the age of the solar system. Glaciers are like conveyor belts, transporting the frozen meteorites for thousands of years and depositing them at the blue ice. Here in Antarctica these meteorites are preserved in the cold and kept fresh. There is little rust that forms.
There is a special procedure that the ANSMET team follows to collect the meteorites. The definition of how to collect meteorites in Antarctica is actually set forth in the Antarctic Treaty. Here’s what a typical day might look like.
The team fans out in a line and uses their snowmobiles. This helps them cover a wide path. They ride slowly over the ice and look for dark spots on the white/blue background. Some of them ride standing up, while others prefer to kneel on their snowmobile seat. They need to be up higher to get a good look at the ice/snow.
The team searches in the direction of the wind, which is often coming from the southeast. The wind carves the ice and if they follow the wind it is a smoother ride on the snowmobile. At the end of a sweep along the ice, they turn around and search back in the other direction, along another section of the ice. If it’s too cold, they mask up and quickly drive back to their starting point. The team shifts over a bit and begins exploring the next section, following the wind again.
When someone finds what they believe is a meteorite, the team stops together. All of the specimens they collect will be shipped back (frozen) to the Johnson Space Center in Houston, and later sent on to the Smithsonian Institution in Washington, D.C. The Smithsonian scientists are the curators of the meteorites. ANSMET teams do not make the final determination of whether or not a specimen is actually a meteorite, that job is reserved for scientists at Johnson Space Center and the Smithsonian.
Just for clarification, a meteorite is a meteoroid that survives atmospheric entry and lands on Earth, either on the ground or the ice. A meteoroid is rock or dust grains floating in space. A meteor is what we commonly call a shooting or falling star. It is the visible path of a meteoroid that enters Earth’s (or another body’s) atmosphere.
The first step in collection, photographing the specimen.
Step two, the specimen is given a number. Look at this little gadget made for this purpose.
Meteorite number 23,265 ready for collection! Notice that there is a centimeter scale on the gadget as well. Each specimen is also measured.
Specimens are picked up by sterilized tongs. If a specimen is partially covered with snow, the tongs can be used to brush the snow away. Every specimen is handled in a clean way.
Specimens are put into bags and labeled.
Last, they are put into larger collection bags.
A flag is placed at the spot the meteorite was found. A GPS reading is taken of the position and later that is doubled-checked back at the camp. If the readings are accurate, the flags are removed.
The team collected 329 meteorites this season. The smallest is 1 x 1 x .5 cm which is fingertip size. The largest is the size of a volleyball, and is 15 kilograms (33 pounds). It was found on what’s called a glacial moraine. A moraine is a ridge of debris deposited at the end of a glacier.
When the group wants to search on a moraine, they do it on foot, because the moraine is covered with rocks and snow, not just ice. It’s like a long strip of rocks. It’s harder to spot the meteorites on the ground in these areas, because there are so many rocks to look at. The group fans out and looks through thousands of rocks on the moraine. Do you see the object that is darker (right middle)?
On the blue ice or the snow, a meteorite is a black dot and the contrast of the dark object on the white/blue ice is easy to see. On a moraine scientists look for specimens that have what’s called a fusion crust. Meteorites plunging through the atmosphere on their way to Earth at a speed of 12 km (7.45 miles) per second get very hot. The rough corners get scorched off and the meteorite takes on a rounded appearance, especially the side of the rock that’s coming toward the Earth. A thin layer (only 1 mm; the thickness of your fingernail) of crust forms on the outside; it’s what is melted on the outside. The inside of the meteorite stays cold. That black outside layer is called the fusion crust.
Looking at the photo above, you can see how the meteorite is a darker color than the rocks in the moraine. Here is a close up below.
Tom told me that there is a higher density of meteorites on a moraine because they have been moved by glaciers, although they are harder to spot. On their best day the group found 50 meteorites in the rocky moraines; on their best day on the ice they found 41 meteorites.
Moraines also have many beautiful rocks and minerals, such as the area shown below. The minerals found in this photo are calcite (white particles), malachite, and azurite. The malachite and azurite are what’s called copper carbonates (they have the blue/green color) because the mineral copper is found in these rocks.
One tool that is often used by geologists is a pick axe.
Look at the beautiful geode they found. There is quartz inside of the geode and agate on the outside.
Back in the United States, scientists can take a sample from the meteorite and make what is called a thin section slide. Basically they attach a small piece of a meteorite to a microscope slide and sand it down until it is so smooth you can’t even feel it on the glass slide. A high-powered microscope can help scientists determine what minerals are in the specimen. They can tell where it came from — Mars, the Moon, or an asteroid belt.
Several types of meteorites were found this season. The most common are called ordinary chondrite meteorites. If you opened a chondrite meteorite, you would see tiny “chondrules” which are mini-sized stone spheres. Carbonaceous condrite meteorites are the oldest and least processed material in the solar system. They are more primitive, and less common. The inside looks like a charcoal briquette (like you would use for grilling out).
Achondrite meteorites are more rare, have been heated, and have no metal inside. They have come from objects that melted and are earlier in formation history. The achondrites are more valuable.
Here are a couple of other specimens that the ANSMET team collected.
Each day was physically demanding work for the team. However, they did take some time to explore their surroundings. They climbed up this mountain area and marveled in the 360 degree views.
Part of the team is shown here taking a break to enjoy that view.
The group celebrated Christmas with presents and a really great dinner. They even cooked a turkey in their camp oven. They told me it barely fit into the oven!
After forty days of working in the field, they got a real treat…a stopover at the South Pole on the way back to McMurdo! Can you tell the team is excited? This is Tom by the South Pole Station sign.
The new South Pole Station is elevated to decrease the drifting up against the buildings.
And here’s Marianne, at the Geographical South Pole.
The Ceremonial South Pole is a red-striped pole with a mirrored ball on top, surrounded by the flags of the twelve original signatories of the Antarctic Treaty, established in 1959.
I’m going to close this post with two cool photos of ice/snow which were taken out in the field. This snow/ice crystal formation came from inside of a crevasse (crack) in the blue ice.
This last photograph shows snow crystals that grow up from the blue ice. They are absolutely beautiful.
Follow the work and adventure of the 2012-2013 ANSMET teams (both Systematic and Recon) on their blog: artscilabs.case.edu/ansmet
Many thanks to Marianne, Tom, and Stan for teaching me more about meteorites and the search for them in Antarctica. SUPER thanks to Tom for all of the photographs in today’s blog.