Field Museum research scientist part of team that discovered a large, rare meteorite in Antarctica

The team of scientists had already combed over miles of Antarctic ice field, ready to turn around at the very end of an 11-day meteorite hunt. Then they spotted something rare.

The international team knew what they were looking at from 100 meters away: a huge meteorite “the size of a gourd,” recalled Field Museum research scientist Maria Valdes, who was part of the team.

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“To put the meteorite’s size in perspective, of the 45,000 meteorites retrieved from Antarctica over the last century, only 100 are this size or larger,” the Field Museum said.

The Jan. 5 discovery was made during a survey of terrain that scientists had never before hunted for meteorites. The lucky team of researchers from America, Belgium and Switzerland found five total meteorites on their 11-day trip, including the big one.

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“We were sort of like pioneers going into the unknown,” Valdes said.

The first seven days were spent on rocky terrain, where ordinary rocks can sometimes be confused with meteorites. The last four days were spent on Antarctica’s blue ice fields, she said.

The ice field searches were done on snowmobiles. The scientists drove in a V-formation, traveling at slower speeds of about 6 mph so that the scientists could survey the region, she said. It was only when they were about to turn around and finish their survey that they spotted the meteorite, Valdes said.

“When we saw this one just sitting by itself in the middle of the blue ice, we all got so excited,” she said. The researchers exchanged hesitant glances. “Because we knew that if we found a meteorite, this was really the mother lode. On the last day, the last hour.”

One telltale clue that the scientists had discovered a meteorite and not a rock was that it was “the size of a bowling ball, but twice the weight of a bowling ball,” Valdes said.

The meteorite was 16.7 pounds, but heft isn’t everything.

“Size doesn’t necessarily matter when it comes to meteorites, and even tiny micrometeorites can be incredibly scientifically valuable,” Valdes said.

The meteorite had what Valdes called a “fusion crust,” meaning that it had a thin glassy crust that showed it had slightly melted when it entered Earth’s atmosphere. The crust was worn down, indicating that the meteorite had long been on the planet.

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The meteorite’s chemistry composition is going to be examined in Belgium, where scientists will “study its make up and search for potential micrometeorites,” the museum said in a news release.

Studying the meteorite will help scientists learn more about the history of the solar system and Earth itself. Meteorites offer scientists a rare look at the chemical compositions of other planets and asteroids. That in turn allows builds a better understanding of Earth’s deep history, which is sometimes “overprinted” compared with “pristine” meteorites, Valdes said.

“All meteorites have something to say about the evolution of Earth,” she said.

The best time to find a meteorite in Antarctica is during polar summer, in December and January, Valdes said. Scientists are drawn to the continent because meteorites are much easier to find in Antarctica’s empty, snowy climate.

But the bits of space are everywhere, covering Earth in a “thin layer of space dust,” she said.

Most of the meteorites found on Earth’s surface are quite small. The space rocks typically break up as they move through the planet’s atmosphere.

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While many are smaller than a grain of sand, the little bits add up. More than 40,000 tons of meteorites that fall to Earth’s surface are smaller than a grain of sand, while only 2 tons of meteorites that make it down here are larger, Valdes said.

The meteorites can and do fall all over the world, she said.

“Just as many meteorites fall in Chicago as they do in a Chicago-sized area of Antarctica,” Valdes said.

Tribune reporter Jake Sheridan contributed.

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