Tiny asteroid disintegrates hours after being discovered
On Saturday, June 1 a boulder-sized asteroid designated 2018 LA was discovered and determined to be on a collision course with Earth, with impact predicted to be just a few hours later. The event proved that Earth is still in the cosmic shooting gallery and could be struck with little-to-no notice.
Because the asteroid was very faint, it was estimated to be approximately 6 feet (2 meters) in diameter, which is small enough that it was predicted to safely burn up in the Earth’s atmosphere. 2018 LA was first discovered by the NASA-funded Catalina Sky Survey, located near Tucson and operated by the University of Arizona.
While there was not enough tracking data to make precise predictions ahead of the asteroid reaching Earth – a swath of possible locations stretching from southern Africa, across the Indian Ocean, and onward to New Guinea were suggested. A bright fireball was reported over Botswana, Africa, early Saturday evening, which matched up with the asteroid’s predicted trajectory.
The asteroid entered Earth’s atmosphere traveling at approximately 10 miles per second (38,000 mph, or 17 kilometers per second) at about 16:44 UTC (9:44 a.m. PDT, 12:44 p.m. EDT, 6:44 p.m. local Botswana time). 2018 LA disintegrated several miles above the surface, generating a fireball that lit up the night sky. The event was observed by several witnesses and captured on webcam video.
The asteroid was nearly as far away as the Moon’s orbit when it was first detected. It appeared as a streak in a series of time-exposure images taken by the Catalina telescope. The data were quickly sent to the Minor Planet Center in Cambridge, Massachusetts, which calculated a trajectory that indicated the possibility of an Earth impact. That data was then sent to the Center for Near-Earth Object Studies (CNEOS) at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, where the automated Scout system also determined that the asteroid was likely to be on an impact trajectory.
Automated alerts were sent out to the community of asteroid observers to obtain further observations of the asteroid, and the Planetary Defense Coordination Office at NASA Headquarters in Washington, DC. Because the asteroid was so small, it was determined to be harmless and NASA issued no further warnings.
While there was some alarm that between the time that the asteroid was detected and impacted with Earth only provided a few hours warning, in the end the size of the tiny chunk of space debris was cited as the determining factor for the apparent lack of fore warning.
“This was a much smaller object than we are tasked to detect and warn about,” said Lindley Johnson, Planetary Defense Officer at NASA Headquarters. “However, this real-world event allows us to exercise our capabilities and gives some confidence our impact prediction models are adequate to respond to the potential impact of a larger object.”
The ATLAS asteroid survey obtained two more observations of the asteroid before impact, which the Scout system used to confirm that impact would occur and narrowed the predicted impact area to southern Africa. Infrasound data collected shortly after the impact clearly detected the event from one of the listening stations deployed as part of the International Monitoring System of the Comprehensive Nuclear-Test-Ban Treaty. The signal is consistent with an atmospheric impact over Botswana.
“The discovery of asteroid 2018 LA is only the third time that an asteroid has been discovered to be on an impact trajectory, said Paul Chodas, manager of the Center for Near-Earth Object Studies (CNEOS) at JPL. “It is also only the second time that the high probability of an impact was predicted well ahead of the event itself.”
Video courtesy of NASA/JPL-Caltech
Jim Sharkey is a lab assistant, writer and general science enthusiast who grew up in Enid, Oklahoma, the hometown of Skylab and Shuttle astronaut Owen K. Garriott. As a young Star Trek fan he participated in the letter-writing campaign which resulted in the space shuttle prototype being named Enterprise. While his academic studies have ranged from psychology and archaeology to biology, he has never lost his passion for space exploration. Jim began blogging about science, science fiction and futurism in 2004. Jim resides in the San Francisco Bay area and has attended NASA Socials for the Mars Science Laboratory Curiosity rover landing and the NASA LADEE lunar orbiter launch.