For only the third time, astronomers have discovered an asteroid just hours before it crashed to Earth. That’s exactly what happened on June 2. Richard Kowalski, senior research specialist for the Catalina Sky Survey based in Tucson Arizona, recorded and observed a fast-moving asteroid. From the observations he calculated an orbit predicting the object’s trajectory would take it straight into the atmosphere over southern Africa within a matter of hours.
A little more than seven hours later at 16:53 Universal Time — early evening in eastern Africa — 2018 LA slammed into the atmosphere over Botswana, a small country which borders South Africa. Eyewitnesses described a orange-and-red, sparking fireball nearly as bright as the sun that exploded in two bright bursts over the countryside. Some heard rumbles like thunder in its wake, while an infrasound recorder in South Africa registered the explosion’s low frequency sound waves. Based on their strength, scientists estimate the asteroid measured between 6.8 and 15 feet (2.1 – 4.6 meters) long and exploded with the power of 300-500 tons of TNT.
Right now, meteor hunters and scientists on the ground, are trying to gather as many reports as possible the better to narrow down the search for possible meteorites that likely survived the explosion. Mike Hankey, who runs the American Meteor Society website, a clearinghouse for bright meteor sightings, is actively seeking reports of the fireball. If you know of anyone who witnessed it, please ask them to fill out this report form. The sooner teams on the ground can look for and potentially gather up fragments the better. Newly fallen meteorites contain tiny amounts of rare, short-lived forms of elements called isotopes than can tell us where they came from and for how long they’ve been in space before they found their “new home” on Earth.
What’s amazing is that the keen-eyed Kowalski has found all three of these self-destructing asteroids. 2008 TC3 was the first, a 4.1-meter object discovered on October 7, 2008 that exploded over Sudan’s Nubian Desert 19 hours later. After many eyewitness interviews, Peter Jenniskens of the SETI Institute put together a search time. In time, more than 600 meteorites with a total weight of 10.5 kilograms were found. The second asteroid, 2014 AA, was nabbed by Kowalski on January 1, 2014 and plunked into the Atlantic Ocean northeast of Brazil about 21 hours later. It was about 10 feet (3 meters) across.
2018 LA became a brilliant meteor captured in this video taken with a security camera from a farm between Ottosdal and Hartebeesfontein, North West South Africa. Barend Swanepoel
Astronomers estimate there are a billion objects this size that cross Earth’s orbit. That’s why they’re called Earth-crossers. A few plunge out of the sky every year but most are only witnessed by satellites because they occur in daylight and over the broad expanse of the oceans, which take up 71% of planet’s surface area. When the hit the atmosphere at speeds in excess of 25,000 mph, they break up into dust or, if we’re lucky, into fragments that land as meteorites.
In this animation, we see can watch the 2018 LA track along its orbit until the time of its fateful Earth crossing. Click to start.
NASA / JPL
That’s what we’re hoping for from 2018 LA — a few fragments to sweeten our understanding of asteroids and how they helped build the solar system. I’ll keep you posted.