Scientists discovered pieces of a meteorite that fell near Berlin on January 21 shortly after midnight. This is a rare discovery, coming from an asteroid identified just before it entered the Earth’s atmosphere. Only a handful of such events In the recent past, they have allowed astronomers to trace the origin of a rock entering the solar system.
The first analyzes of the fragments revealed something equally rare. The meteorite is an aubrite, a class of unknown origins that some scientists believe could be pieces of the planet Mercury. They are so rare that they made up only 80 of the approximately 70,000 meteorites collected on Earth before last month’s event.
“It’s really exciting,” said Sara Russell, a meteorite expert at the Natural History Museum in London. “There are very, very few aubrites.”
The asteroid that became the meteorite (or rather meteorite fragments) was first spotted by Krisztián Sárneczky, a Hungarian astronomer, three hours before it impacted the Earth’s atmosphere. A network of cameras followed the arrival of the rock, 2024 BX1, as it fell near Ribbeck, a village outside Berlin. Estimates suggest the rock was tiny, measuring less than three feet. It still produced a bright flash that cameras in many parts of Europe picked up.
As soon as he heard the news of the meteorite fall, Peter Jenniskens, an astronomer at the SETI Institute in California, I bought a plane ticket.
“I found out Saturday afternoon,” he said. “Late Saturday evening I was on a plane to Berlin.”
During a nine-hour layover in Newark, Dr. Jenniskens calculated where pieces of the meteorite might be found so that when he landed early Monday morning, he and nearly two dozen students and volunteers could immediately start searching for fragments.
For days they roamed the fields around Ribbeck. “We didn’t find anything,” he said.
But this Thursday, January 25, a Polish team of meteor hunters announced that they had found the first piece of the meteorite. “They could show us what to look for,” Dr. Jenniskens said. The meteorites were not black, as might be expected when passing through the atmosphere, but light, like terrestrial rocks.
Using this information, in just two hours, a member of Dr. Jenniskens’ team, a student from Freie Universität Berlin named Dominik Dieter, found a meteorite just above the ground. Others were quickly spotted.
“It was amazing,” Dr. Jenniskens said. “We found more than 20 fragments.”
Researchers from the Natural History Museum in Berlin analyzed the minerals contained in the fragments using an electron microprobe. This revealed that the rocks appeared to be aubrites. This was the first time such meteorites had been collected in a monitored fall.
The source of the aubrites, named for the French town of Aubres near where they were first found, remains mysterious because their composition does not match other known sources of meteorites in the solar system. Some research suggests that these are fragments of the planet Mercury, but not all scientists support this origin story.
If the aubrites came directly from Mercury, 2024 BX1 should have come from the inner solar system. However, tracing its trajectory, it appears that the asteroid’s initial orbit was much wider and outside Earth’s orbit.
“So this object cannot come to us directly from Mercury,” said Marc Fries, a planetary scientist at NASA’s Johnson Space Center.
It is possible, however, that aubrites were ejected from Mercury long ago into the asteroid belt between Mars and Jupiter, forming a group called E-type asteroids. The orbit of 2024 BX1 does not completely rule out this idea, although Dr. Fries remains skeptical.
Whatever their origin, the fragments of 2024 BX1 will prove scientifically fascinating. “I’m sure it will be a priority to find out what its composition is and how it compares to other meteorites,” Dr Russell said.
Tracking such small asteroids before they reach Earth’s atmosphere is also crucial for defend the planet against asteroids. Davide Farnocchia, of NASA’s Center for Near-Earth Object Studies, said smaller objects from space still go undetected, but can pose problems for people on the ground, such as 65-foot-wide Chelyabinsk meteor which exploded over Russia in 2013 and injured hundreds of people. Knowing the trajectories in advance could give people time to get to safety.
“If you could send out a warning, no one would get hurt,” he said.