Over 100 participants from 18 countries – including NASA scientists and the agency’s NEOWISE mission – took part in the international exercise.

PASADENA, Calif. (NASA PR) — Watching the skies for large asteroids that could pose a hazard to the Earth is a global endeavor. So, to test their operational readiness, the international planetary defense community will sometimes use a real asteroid’s close approach as a mock encounter with a “new” potentially hazardous asteroid. The lessons learned could limit, or even prevent, global devastation should the scenario play out for real in the future.

Models and lab tests suggest the asteroid could be venting sodium vapor as it orbits close to the Sun, explaining its increase in brightness.

PASADENA, Calif. (NASA PR) — As a comet zooms through the inner solar system, the Sun heats it, causing ices below the surface to vaporize into space. The venting vapor dislodges dust and rock, and the gas creates a bright tail that can extend millions of miles from the nucleus like an ethereal veil.