In the early hours of Nov. 19, the skies over southern Ontario, Canada, lit up as a tiny asteroid harmlessly streaked across the sky high in Earth’s atmosphere, broke up, and likely scattered small meteorites over the southern coastline of Lake Ontario. Roughly 1 meter (3 feet) wide, the asteroid was detected 3.5 hours before impact, making this event the sixth time in history a small asteroid has been tracked in space before impacting Earth’s atmosphere.

Asteroid 2022 WJ1 was discovered by LPL's Catalina Sky Survey (CSS) on the evening of Nov. 18 during routine search operations for near-Earth objects. CSS observations were quickly reported to the Minor Planet Center and the data were then automatically posted to the Near-Earth Object Confirmation Page.

NASA’s Scout impact hazard assessment system automatically fetched the new data from that page and began calculating the object’s possible trajectory and chances of impact. Seven minutes after the asteroid was posted on the confirmation page, Scout had determined it had a 25% probability of hitting Earth’s atmosphere, with possible impact locations stretching from the Atlantic Ocean off the East Coast of North America to Mexico. More observations were then provided by the astronomical community to better refine the asteroid’s trajectory and possible impact site.

As CSS continued to track the asteroid over the next few hours, Scout used this new data to update the asteroid’s trajectory and the system’s assessment of the chance of impact, posting those results on the hazard-assessment system’s webpage.

2022 WJ1 is the fourth pre-impact asteroid discovered so far by CSS and attests to the ability of the survey to rapidly find and enable the orbit characterization of potentially hazardous objects.