Two meteors recently hit Earth just 27 hours apart. The first of the two, which fell on June 1 over southwest China, was captured on video by bystanders, but there is very little information beyond that.
Researchers at the Catalina Sky Survey in Arizona detected the second one that burned up over Botswana on June 2, 8 hours before entering Earth’s atmosphere. After a streak showed up on a series of time-lapse telescope images, astronomers determined that the rock – dubbed 2018 LA – was relatively small and on a collision course with Earth.
At just about 2 metres across, 2018 LA was determined not to be a risk because it would likely burn up almost completely as it hurtled through the atmosphere. This is only the third time astronomers have detected an object set to hit Earth’s atmosphere before it arrived.
The small size that made 2018 LA harmless also made it difficult to detect, especially since the telescopes that would find it only operate at night and do not observe the entire sky.
“There are probably about a billion near-Earth objectsof this size, but we’ve only spotted about 40 that are less than 3 metres across,” says Peter Vereš at the Minor Planet Center in Massachusetts.
“Metre-scale asteroids like these are very faint until they get very close to our planet: they can only be discovered within the last day or so before impact,” says Paul Chodas of the Center for Near-Earth Object Studies at NASA’s Jet Propulsion Laboratory.
“The telescopes also have to be searching the right part of the sky to catch one of these tiny asteroids because they move rapidly across the sky when they are so close.” Larger, potentially dangerous asteroids are both more rare and easier to detect.
On average, about 6 objects this size hit our atmosphere every year, Vereš says. Despite the fact that both of these meteors lit up the skies in the same weekend, they’re probably not related. “Coincidences happen,” he says.