Hot on the trail of Antarctic meteorites | Science News for Students

Hot on the trail of Antarctic meteorites

Each year, scientists scour the frozen continent for space rocks
Jan 11, 2018 — 6:45 am EST
ANSMET meteorite collection
Each year, groups of scientists with the Antarctic Search for Meteorites (ANSMET) project spend weeks camping on ice fields in Antarctica. Using snowmobiles, they travel about looking to find and bring back meteorites. Here's a group that has just met with success.

NASA

It’s a clear summer day in the Transantarctic Mountains. Being January, the temperature here in the vast emptiness of Antarctica is a relatively balmy minus 18 degrees Celsius (0 Fahrenheit). Geologist Stanley Love normally works in Houston, Texas. Now he and six others scientists were zipping across the dazzling white ice on snowmobiles. They were loaded with tents, stoves, sleeping bags and food. For the next six weeks, this team would be camping on Earth’s coldest, most hostile continent. Harsh? Absolutely. But it’s the only way to accomplish their mission: finding meteorites.

Meteorites are rocks from space that have crash-landed on Earth. Before they land, they’re called meteors. They can light the sky as “shooting stars.” Once here, they can teach us things we can’t learn from Earth rocks. Many meteorites are old. They date from the early days of our solar system, 4.6 billion years ago. No Earth rocks are that old. Meteorites also can carry clues about where they came from, which might be the moon or Mars. No wonder scientists are in hot pursuit of them.

Plenty of meteors enter Earth’s atmosphere each year. Most burn up. Still, many reach our planet’s surface. Up to 84,000 meteorites bigger than a marble fall to Earth every year.

Stan Love
Stan Love poses next to a meteorite he found.
ANSMET/Case Western University

That’s a lot of meteorites. But most are nearly impossible to find. They may be hidden by plant leaves. Or they might be mixed up with Earth rocks. Or, they might have sunk into deep water. But in the vast emptiness of Antarctica, spotting meteorites can be as easy as black on white. That’s why, for decades, teams of scientists like Love’s have braved Antarctica’s extreme conditions to look for them. A research group called the Antarctic Search for Meteorites, or ANSMET, coordinates these expeditions.

When a meteorite lands in Antarctica, it has already traveled more than 1,600,000 kilometers (about a million miles) through space. Once picked up by scientists like Love, it now begins a new journey. The rocks eventually travel to the Washington, D.C. area. They go to the Smithsonian Institution’s meteorite library. And from there, tiny pieces of the rocks journey all over the world. They are lent to scientists who probe them for clues to Earth’s beginnings — and even hints of alien life.

On the hunt

Out on the ice, Love and his colleagues spot a dark speck. Like hunters on a chase, the team of snowmobile riders swerve toward it.

The rock is about the size of a golf ball. Is it a meteorite? Chances are good. After all, out here, where else would a rock come from but from the sky? Still, the scientists look for surefire clues. The rock is dark and dense. And it has a fusion crust — the melted coating formed by intense heat as it fell though Earth’s atmosphere.

Meteorite RBT 04262
Meteorite RBT 04262 as it was found in Antarctica by Love’s team in 2004.
ANSMET/NASA

Success! This one is indeed a meteorite.

With the space rock on board, the scientists zoom off again. They’re scanning the vast whiteness as they speed across the snow. Love and his team zip to the next spot. Meanwhile, another ANMSET team has picked up even more meteorites. They label one little rock RBT 04262. RBT stands for Roberts Massif, the area in Antarctica’s Transantarctic Mountains close to where it was found. The 04 identifies the year: 2004. The next three numbers, 262, identify the meteorite as the 262nd to be collected that season.

In an average six-week field season, ANSMET teams will collect 550 meteorites. That’s far more than at any other location on Earth.

“It isn’t just that meteorites are easy to spot here,” says Love. “The flow of the ice can actually concentrate the rocks.” The ice is slowly moving, he explains. The flow can concentrate meteorites in certain places, such as against mountains where old ice is brought to the surface. What’s more, Antarctica’s dry frozen environment keeps them preserved. In addition, the constant winds scour the ice. That can expose meteorites that might have landed hundreds of thousands of years earlier.

Besides being a geologist, Love has another great qualification for an Antarctic meteorite hunter. He’s an astronaut at NASA. He served on NASA training expeditions to practice for the intense conditions in space. (NASA is short for the National Aeronautics and Space Administration.) Then, in 2008 he spent 12 days on a mission to the International Space Station. Such out-of-this-world experiences have surprising similarities to camping on a remote ice sheet. It’s the isolation. Living in seclusion with a small group is a challenge no matter where you are. And in both places, even daily routines can be out-of-this world tough. For example, Love points out, “it’s super hard to take a bath.”

Astronaut Stanley Love
Stanley Love, an astronaut, now searches for meteorites in Antarctica.
NASA

To weather such a trip, whether it’s to Antarctica or space, you need to be even-keeled, he adds, and not easily stressed. Otherwise, “little things can really start to bother you about people,” he says. And, like bathing, there are other parallels between space exploration and camping in Antarctica. In fact, astronauts often go to Antarctica for training before they head into space.

Back on the ice, the meteorite hunt is over. The team returns by plane to McMurdo Station. That’s the U.S research center on the tip of Antarctica’s Ross Island. There, the scientists prepare the meteorites for shipment. Each rock goes in a separate bag, which is kept frozen to keep earthly contaminants away. The meteorites fly, still frozen, to the Johnson Space Center in Houston, Texas. There, NASA geologists classify, weigh and photograph each space rock.

Meanwhile, Love and the other team members can finally take a hot shower and head home. They have no idea what the meteorites they found will reveal. Yet they know it was worth the effort. “Getting those samples is as much trouble as it gets,” Love says. “But they tell us where we come from.”

Out-of-this-world library

From the Johnson Space Center, the meteorites are shipped to one of the world’s largest meteorite libraries. It’s inside the Smithsonian Institution’s Museum Support Center in Suitland, Md. There, geologist Cari Corrigan has been sorting, storing and tracking meteorites since 2008. Corrigan spends her days surrounded by cabinet after cabinet full of meteorite chips. There are around 17,000.

The dime-sized chips are set into thin glass slides or stored in plastic vials. They are housed in a special “clean” room. There, the cabinets are pressurized with nitrogen. This preserves the meteorites by keeping them dry and safe from rusting (due to reactions with oxygen), or from picking up contaminants, such as dust or organic material (like skin). Indeed, to help prevent contamination, Corrigan and her colleagues wear protective gear. (Watch the video below for a tour of Corrigan's archive of space rocks.)

Corrigan has worked with so many meteorites that geologists even named a space rock after her. It’s called 9924 Corrigan. The rock is currently whizzing around the solar system. But who knows. Maybe someday a chunk of it will land in Antarctica.

Most meteorites got their start as stray chunks that broke off asteroids, Corrigan explains. Many came from the asteroid belt. That’s a zone of space rocks located between the orbits of Mars and Jupiter. The region is full of iron-rich chunks that formed during the beginning of the solar system. But they never became part of a larger planetary body. A few meteorites come from other bodies, notably the moon or Mars. In those cases, the meteorites are bits of rock that were thrown into space by large, crater-forming meteorite impacts.

To identify where a meteorite came from, scientists study the rock’s isotopes. These are forms of the same element that have different numbers of neutrons in the nucleus. Oxygen, for example, can have 16, 17 or 18 neutrons. Meteorites from different places — Mars or the moon, for example — have their own unique ratio of oxygen isotopes. That ratio can tell scientists where the space rock came from.

About 85 percent of the meteorites in Antarctica are a type called ordinary chondrites (KON-drytes). They come from the asteroid belt. They’re interesting because they provide clues to the birth of our solar system. But it’s the other 15 percent of meteorites that really excite scientists. They contain a more unusual mix of ingredients. And, of these meteorites, the most interesting ones are the very, very few — less than one-half of one percent — that come from either Mars or the moon.

One of Corrigan’s roles is to analyze meteorites to identify any unusual characteristics.  “If it’s just a run of the mill, out-of-this-world rock, it goes into storage,” she says. But if it is unusual, geologists will want to study it more closely. In those cases, Corrigan, or geologists at Johnson Space Center, create a thin slice that can be analyzed in the laboratory.

RBT 04262 was one of the really unusual meteorites. In 2007, geologists at the Johnson Space Center announced that its composition and oxygen isotope ratio revealed that the rock must have come from Mars. They estimated that it was 225 million years old. The scientists also studied isotopes that showed the rock’s exposure to cosmic rays, a type of radiation found in space. Those data suggest that the meteorite had crashed into Antarctica some 700,000 years ago!

As a meteorite librarian, Corrigan also is in charge of loaning out pieces of meteorites when scientists request it. And once news about an unusual meteorite gets out, those requests come flying in.

Message from Mars?

It’s 2011, and Danny Glavin is crushing it. Crushing a meteorite, that is. Glavin works at NASA’s Goddard Space Flight Center in Greenbelt, Md. He and his colleagues are studying a meteorite chip from Corrigan’s collection. Not just any chip, either. It’s a piece of RBT 04262.

“We’re searching for the chemical building blocks of life,” Glavin says. As an astrobiologist, he looks for any clues to biological activity beyond Earth. He’s particularly interested in organic compounds known as amino acids. They are the building blocks of proteins, and essential to life on Earth. Finding amino acids in an extraterrestrial object could suggest that at least some of the ingredients for life exist beyond Earth.

Danny Glavin in lab
Danny Glavin with the liquid-chromatography mass-spectrometry instruments at NASA’s Astrobiology Analytical Lab. It’s located at the Goddard Space Flight Center. He used the instruments to detect amino acids in a Martian meteorite collected in Antarctica.
NASA

When Glavin heard that RBT 04262 was from Mars, he couldn’t wait to get his hands on a piece of it. Finally, in 2011, he got a peanut-sized chip. In the lab, he and his colleagues processed the sample as they do every meteorite piece they analyze. First the researchers crush it up in a sterile environment. “No sneezing on it!” he says. Next, they boil the crushed rock in sterile water. “We end up making what we call a meteorite tea,” he explains. “Then, we analyze it using a mass spectrometer.” This instrument can identify which chemical elements are present.

Sure enough, RBT 04262 contained amino acids. “Four stood out,” he recalls. “They were unusual.” Three in particular had properties not typically found in Earthly amino acids. “That was pretty strong evidence that we were looking at extraterrestrial amino acids,” he said. “We think these amino acids are from Mars.”

But Glavin and his team wanted to be sure. “Usually, amino acids are from contamination in Antarctica,” he says. Antarctica may look devoid of life. But there are plenty of living things, including people who could have transferred amino acids to the space rock. If the amino acids turned out to be from Earth, then the meteorite would be what Glavin jokingly calls a meteor-wrong. “We requested another piece [of the rock] and found the same thing,” he says. “We almost didn’t believe it. I was kind of thrilled and scared at the same time.”

By 2012, Glavin and his colleagues were sure enough about their findings to publish them in the journal Meteoritics & Planetary Science. Glavin emphasizes that they haven’t actually found direct evidence of life on Mars. But, in the search for extraterrestrial life, they have discovered something very important. There is a way to create the building blocks of life somewhere other than Earth, they now know.

Current evidence suggests that Mars was inhabitable only until 3.5 billion years ago, Glavin notes. At just over 200 million years old, RBT 04262 is far too young to provide clues that far back. “I would love to find an older rock that was from that time. That would be my dream,” says Glavin. “Who knows, maybe it’s sitting in Antarctica right now, waiting to be collected.”

Cari Corrigan and colleague Linda Welzenbach show off the room that houses the Smithsonian’s meteorite collection.
Smithsonian

Power Words

(for more about Power Words, click here)

alien     A non-native organism. (in astronomy) Life on or from a distant world.

amino acids     Simple molecules that occur naturally in plant and animal tissues and that are the basic building blocks of proteins.

Antarctica     A continent mostly covered in ice, which sits in the southernmost part of the world.

archive     (adj. archival) To collect and store materials, including sounds, videos, data and objects, so that they can be found and used when they are needed. The term is also for the process of collecting and storing such things. People who perform this task are known as archivists.

asteroid     A rocky object in orbit around the sun. Most asteroids orbit in a region that falls between the orbits of Mars and Jupiter. Astronomers refer to this region as the asteroid belt.

astrobiology     The study of life everywhere in the universe, including on Earth and in space. People who work in this field are known as astrobiologists.

astronaut     Someone trained to travel into space for research and exploration.

atmosphere     The envelope of gases surrounding Earth or another planet.

average     (in science) A term for the arithmetic mean, which is the sum of a group of numbers that is then divided by the size of the group.

chemical     A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.

chondrite     A stony meteorite, usually one that has chondrules — tiny embedded minerals containing silica that formed at high temperatures as droplets of molten rock and then collected and fused together.

colleague     Someone who works with another; a co-worker or team member.

compound     (often used as a synonym for chemical) A compound is a substance formed when two or more chemical elements unite (bond) in fixed proportions. For example, water is a compound made of two hydrogen atoms bonded to one oxygen atom. Its chemical symbol is H2O.

constant     Continuous or uninterrupted.

contaminant     Pollutant; a chemical, biological or other substance that is unwanted or unnatural in an environment (such as water, soil, air, the body or food). Some contaminants may be harmful in the amounts at which they occur or if they are allowed to build up in the body or environment over time.

continent     (in geology) The huge land masses that sit upon tectonic plates. In modern times, there are six established geologic continents: North America, South America, Eurasia, Africa, Australia and Antarctica. In 2017, scientists also made the case for yet another: Zealandia.

cosmic rays     Very high-energy particles, mostly protons, that bombard Earth from all directions. These particles originate outside our solar system. They are equivalent to the nucleus of an atom. They travel through space at high rates of speed (often close to the speed of light).

crater     A large, bowl-shaped cavity in the ground or on the surface of a planet or the moon. They are typically caused by an explosion or the impact of a meteorite or other celestial body. Such an impact is sometimes referred to as a cratering event.

crust     (in geology) Earth’s outermost surface, usually made from dense, solid rock.

element     (in chemistry) Each of more than one hundred substances for which the smallest unit of each is a single atom. Examples include hydrogen, oxygen, carbon, lithium and uranium.

environment     The sum of all of the things that exist around some organism or the process and the condition those things create. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature and humidity (or even the placement of components in some electronics system or product).

expedition     A journey (usually relatively long or over a great distance) that a group of people take for some defined purpose, such as to map a region’s plant life or to study the local microclimate.

extraterrestrial     (ET) Anything of or from regions beyond Earth.

friction     The resistance that one surface or object encounters when moving over or through another material (such as a fluid or a gas). Friction generally causes a heating, which can damage a surface of some material as it rubs against another.

geology     The study of Earth’s physical structure and substance, its history and the processes that act on it. People who work in this field are known as geologists. Planetary geology is the science of studying the same things about other planets.

ice sheet     A broad blanket of ice, often kilometers deep. Ice sheets currently cover most of Antarctica. An ice sheet also blankets most of Greenland. During the last glaciation, ice sheets also covered much of North America and Europe.

International Space Station     An artificial satellite that orbits Earth. Run by the United States and Russia, this station provides a research laboratory from which scientists can conduct experiments in biology, physics and astronomy — and make observations of Earth.

iron     A metallic element that is common within minerals in Earth’s crust and in its hot core. This metal also is found in cosmic dust and in many meteorites.

isotope     Different forms of an element that vary somewhat in mass (and potentially in lifetime). All have the same number of protons but different numbers neutrons in their nucleus.

journal     (in science) A publication in which scientists share their research findings with experts (and sometimes even the public). Some journals publish papers from all fields of science, technology, engineering and math, while others are specific to a single subject.

Jupiter     (in astronomy) The solar system’s largest planet, it has the shortest day length (10 hours). A gas giant, its low density indicates that this planet is composed of light elements, such as hydrogen and helium. This planet also releases more heat than it receives from the sun as gravity compresses its mass (and slowly shrinks the planet).

Mars     The fourth planet from the sun, just one planet out from Earth. Like Earth, it has seasons and moisture. But its diameter is only about half as big as Earth’s.

massif     (in geology) Part of a mountain or mountain range that is independent of the neighboring rock.

mechanism     The steps or process by which something happens or “works.” It may be the spring that pops something from one hole into another. It could be the squeezing of the heart muscle that pumps blood throughout the body. It could be the friction (with the road and air) that slows down the speed of a coasting car. Researchers often look for the mechanism behind actions and reactions to understand how something functions.

metal     Something that conducts electricity well, tends to be shiny (reflective) and malleable (meaning it can be reshaped with heat and not too much force or pressure). 

meteor     A lump of rock or metal from space that hits the atmosphere of Earth. In space it is known as a meteoroid. When you see it in the sky it is a meteor. And when it hits the ground it is called a meteorite.

meteorite     A lump of rock or metal from space that passes through Earth’s atmosphere and collides with the ground.

moon     The natural satellite of any planet.

NASA     Short for the National Aeronautics and Space Administration. Created in 1958, this U.S. agency has become a leader in space research and in stimulating public interest in space exploration. It was through NASA that the United States sent people into orbit and ultimately to the moon. It also has sent research craft to study planets and other celestial objects in our solar system.

neutron     A subatomic particle carrying no electric charge that is one of the basic pieces of matter. Neutrons belong to the family of particles known as hadrons.

nitrogen     A colorless, odorless and nonreactive gaseous element that forms about 78 percent of Earth's atmosphere. Its scientific symbol is N. Nitrogen is released in the form of nitrogen oxides as fossil fuels burn.

nucleus     Plural is nuclei. (in astronomy) The rocky body of a comet, sometimes carrying a jacket of ice or frozen gases. (in physics) The central core of an atom, containing most of its mass.

orbit     The curved path of a celestial object or spacecraft around a star, planet or moon. One complete circuit around a celestial body.

organic     (in chemistry) An adjective that indicates something is carbon-containing; a term that relates to the chemicals that make up living organisms.

oxygen     A gas that makes up about 21 percent of Earth's atmosphere. All animals and many microorganisms need oxygen to fuel their growth (and metabolism).

parallel     An adjective that describes two things that are side by side and have the same distance between their parts. In the word “all,” the final two letters are parallel lines. Or two things, events or processes that have much in common if compared side by side.

planet     A celestial object that orbits a star, is big enough for gravity to have squashed it into a roundish ball and has cleared other objects out of the way in its orbital neighborhood. To accomplish the third feat, the object must be big enough to have pulled neighboring objects into the planet itself or to have slung them around the planet and off into outer space.

planetary science     The science of planets other than Earth.

plastic     Any of a series of materials that are easily deformable; or synthetic materials that have been made from polymers (long strings of some building-block molecule) that tend to be lightweight, inexpensive and resistant to degradation.

protein     A compound made from one or more long chains of amino acids. Proteins are an essential part of all living organisms. They form the basis of living cells, muscle and tissues; they also do the work inside of cells. Among the better-known, stand-alone proteins are the hemoglobin (in blood) and the antibodies (also in blood) that attempt to fight infections. Medicines frequently work by latching onto proteins.

radiation     (in physics) One of the three major ways that energy is transferred. (The other two are conduction and convection.) In radiation, electromagnetic waves carry energy from one place to another. Unlike conduction and convection, which need material to help transfer the energy, radiation can transfer energy across empty space.

ratio     The relationship between two numbers or amounts. When written out, the numbers usually are separated by a colon, such as a 50:50. That would mean that for every 50 units of one thing (on the left) there would also be 50 units of another thing (represented by the number on the right).

slide     In microscopy, the piece of glass onto which something will be attached for viewing under the device’s magnifying lens.

solar system     The eight major planets and their moons in orbit around our sun, together with smaller bodies in the form of dwarf planets, asteroids, meteoroids and comets.

spectrometer     An instrument that measures a spectrum, such as light, energy, or atomic mass. Typically, chemists use these instruments to measure and report the wavelengths of light that it observes. The collection of data using this instrument, a process is known as spectrometry, can help identify the elements or molecules present in an unknown sample.

star     The basic building block from which galaxies are made. Stars develop when gravity compacts clouds of gas. When they become dense enough to sustain nuclear-fusion reactions, stars will emit light and sometimes other forms of electromagnetic radiation. The sun is our closest star.

sterile     An adjective that means devoid of life — or at least of germs.

unique     Something that is unlike anything else; the only one of its kind.

vegetation     Leafy, green plants. The term refers to the collective community of plants in some area. Typically these do not include tall trees, but instead plants that are shrub height or shorter.

weather     Conditions in the atmosphere at a localized place and a particular time. It is usually described in terms of particular features, such as air pressure, humidity, moisture, any precipitation (rain, snow or ice), temperature and wind speed. Weather constitutes the actual conditions that occur at any time and place. It’s different from climate, which is a description of the conditions that tend to occur in some general region during a particular month or season.

Citation

Journal: M.P. Callahan et al. A search for amino acids and nucleobases in the Martian meteorite Roberts Massif 04262 using liquid chromatography-mass spectrometry. Meteoritics & Planetary Science. Vol. 48, May 2013, p. 786-795. doi: 10.1111/maps.12103. 

ANSMET, The Antarctic Search for Meteorites