Meteorite Hunting on the Ice

Antarctica is home to the South Pole, penguins of many kinds, and lots and lots of ice. ASU geologist Laurie Leshin says that it also is the best place on Earth to find meteorites.

What on Earth would convince a perfectly sane Arizona native to spend six weeks camping out in one of the coldest, windiest parts of Antarctica? For Laurie Leshin, an Arizona State University geologist, the answer is meteorites.

Meteorites are rocks that fall to the Earth from outer space. They come from asteroids, Mars, and our own moon. Meteorites fall everywhere on Earth, but Antarctica is the best place to find them.

“They are easy to distinguish on the ice. We typically go to places where there aren’t Earth rocks for miles. So meteorites are easy to see—black rock on white ice,” says Leshin.

“The flow of ice also concentrates meteorites in some regions. They get incorporated into the ice like chocolate chips in a cookie,” she explains. “The ice flows and sometimes runs into a barrier, like a mountain range. Then the winds erode the ice and expose the meteorites.”

During the winter of 1996, Leshin traveled to Antarctica as a member of the Antarctic Search for Meteorites Program (ANSMET), funded by the U.S. National Science Foundation. The program sends a group of scientists to Antarctica every year. Their job is to find and retrieve as many meteorites as they can.

Not Your Usual Vacation
The toughest part of the job may be getting to the research sites. Leshin and her team first flew to New Zealand, where they boarded a C-130 military plane for the eight-hour flight to Antarctica.

“It’s not like a commercial flight,” Leshin says. “The seats are uncomfortable, and there’s no hot dinner and a movie!”

The plane landed at McMurdo Station, the biggest U.S. base in Antarctica. At McMurdo, the ANSMET team was trained to live and work in Antarctica’s frigid environment. They also picked out food for the trip and loaded it on sleds.

“It’s great—you can leave your frozen meat outside and it doesn’t go bad!” jokes Leshin.

Next, the group took another plane to the field site. Because there is no airport for landings, the plane has skis on the bottom instead of wheels. Before landing, the pilot zoomed down to the ground, dragged the skis along at full speed, and then took off again.

“It feels like you’re crashing!” says Leshin. “They do this to test the ice and to make a kind of runway for the landing.”

The team camped one night at the landing site, then dragged their sleds and snowmobiles to the final campsite. They camped in small tents, using “the warmest down sleeping bags they make,” according to Leshin. The team members even cooked inside the tent, using little stoves that also helped to keep them warm.

“The biggest fear in Antarctica among the experienced campers is that with all the wind, the tents will catch fire from the stoves. You keep a knife in the tent in case you have to cut your way out in an emergency,” says Leshin.

The average temperature was 5 degrees below zero Fahrenheit. The wind chill factor made it feel like 30 to 40 degrees below zero.

“It was really cold and blowing hideously at the camp. They call our program ‘the harshest deep field camp on the continent,’” Leshin says. Why? “Because the places where meteorites are found tend to be the windiest, most hideous places.

“It’s intense, but you know what? I’d love to go back!” she adds.

Understanding Meteorites
Leshin’s team found 400 meteorites during their stay, which is average for ANSMET trips. Since the program began, the world’s collections of meteorites have increased tenfold. Today, about 25,000 meteorites are housed in museums and universities around the globe.

The meteorites found through ANSMET belong to the U.S. government. Eventually, they all end up at the Smithsonian Institution in Washington, D.C. But scientists from all over the world can request samples of these meteorites for study.

Leshin often requests these kinds of samples for her research. She studies the chemistry of meteorites in order to understand environments outside the Earth.

ASU is home to the largest university-based meteorite collection in the world. The Center for Meteorite Studies has about 1,500 specimens. Leshin uses many of these meteorites in her work, along with others from collections around the world.

She studies these meteorites using a device called an ion microprobe. The microprobe shoots a beam of electrically charged atoms—ions—at the rock sample. When the ions smash into the rock, tiny particles sputter off of the surface. These grains get sucked into the machine, which spreads the particles out according to their mass, from light to heavy. The device can identify the particles based on their mass, and find out what the meteorite is made of.

Scientists use meteorite research to better understand how our solar system began, and how life developed. For example, some meteorites contain amino acids, which are the building blocks of proteins. Proteins are an essential part of all living things.

“These meteorites offer a record of the steps leading up to the formation of life,” says Leshin. “It’s really the only record of those steps that we can see. Here on Earth, the record has been wiped out, because the rocks here have undergone so many changes and because existing living things contaminate any historical evidence.”

Cooking Up a Solar System
The vast majority of meteorites are tiny pieces of asteroids. Asteroids have been around since the beginning of the solar system. The meteorites from asteroids are the oldest things ever dated. Some are about 4.566 billion years old.

Billions of years ago, our solar system began as a big cloud of gas and dust. As the gas and dust collected, it began to collapse on itself. As this gas cloud got smaller, it spun faster, just like a figure skater spins faster when she pulls her arms in close. This made the solar system flatten out, like a pizza flattens out when a chef spins it really fast.

The solar system became very hot as it collapsed. When the spinning slowed, the solar system began to cool down, and grains of dust stuck together to form asteroids. These asteroids smashed together and eventually formed planets.

Jupiter was one of those planets. Because Jupiter was so big, its gravitational pull was strong enough to tug asteroids apart whenever they tried to pull together into new planets. The result is a belt of thousands of asteroids that now orbit the sun between Mars and Jupiter.

“Jupiter also cleans out a lot of debris and protects us from it,” says Leshin. “Astrobiologists have lots of questions. One of the big questions is: Does a solar system need a big planet like Jupiter in order to form life?”

How to Spot a Meteorite
Not all meteorites are found in Antarctica. However, meteorites are much harder to recognize when surrounded by regular Earth rocks. Even so, people occasionally discover new meteorites just lying around.

How can you tell if you’ve found a space rock?

First of all, meteorites get burnt when they enter Earth’s atmosphere. As a result, meteorites are black and crusty on the outside. Also, nearly all meteorites will attract a magnet.

ASU scientists will examine any rock you find that you think might be a meteorite. But don’t get your hopes up too high. Most of the rocks they see are just plain old Earth rocks.

“We look at about 500 meteor-wrongs each year,” says Leshin.—Diane Boudreau