Meteorite fragments recovered from ocean

First ocean search for meteorites aims to recover remnants of a meteor observed to have fallen last March.
By Laurel Kornfeld | Nov 19, 2018
For the first time, scientists may have intentionally recovered meteorite fragments from the ocean floor.

A falling meteor estimated to have a diameter of 15.5 miles (25 km) was detected by the National Oceanic and Atmospheric Administration (NOAA) on March 7. Observed by many people, it produced a sonic boom and fell into the Pacific Ocean off Washington state.

Marc Fries, cosmic dust curator for NASA, estimates the meteor could have produced 4,400 lbs (2,000 kg) of meteorites, with the largest weighing as much as 9.7 lbs (4.4 kg) and having a diameter of approximately five inches (12 cm).

"This is the largest meteorite fall I've seen in 20-plus years of radar data," he emphasized.

Based on the trajectory of its fall, scientists know the meteor landed on soft seabed, where it would have a decent chance of remaining intact.

In the past, scientists inadvertently discovered meteorite fragments on the sea floor even though they had not been searching for them.

On July 1, scientists from NOAA's Olympic Coast National Marine Sanctuary, NASA, the University of Washington (UW), and the nonprofit Ocean Exploration Trust teamed up in an effort to search the sea floor for meteorite remnants. Using the Exploration Vessel Nautilus, they searched a 0.4-mile (one square km) region of the Olympic Coast National Marine Sanctuary from approximately 330 feet (100 meters) above the ocean floor.

One day later, they sent two remote-controlled submarines equipped with cameras to the sea floor. If the cameras revealed any objects of interest, the submarines were directed to retrieve them either by use of magnets or a suction pump.

After failing to locate any meteorites, the scientists concluded most or all had sunk into the soft seafloor.

However, during the six hours the researchers spent studying sediment returned from the site, they recognized meteorite fragments in the last sample they collected.

"The meteorite fragments are small, melted pieces of rock," Fries noted, explaining that the rock fragments are coated by a substance that resembles pottery glaze, produced by "flash-melting" of the rock as the meteor descends through Earth's atmosphere.

"[They are] basically made of glass, and flash-meted glassy materials do not last long in seawater," he explained. The fact that they look like they came from a small pit on the ocean floor indicates they are the products of something that fell, he added.

As a next step, the scientists plan to conduct laboratory analyses on the fragments to determine their composition. "If they are meteoritic in origin, we can tell what kind of meteorite they came from," Fries said.

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