For a few seconds early Thursday, night turned into day as an extremely bright fireball lit the pre-dawn sky over much of Arizona, blinding all-sky meteor cameras as far away as western New Mexico.
Based on numerous eyewitness accounts, a small asteroid estimated at 10 feet (3 meters) in diameter – with a mass in the tens of tons and a kinetic energy of approximately 10 kilotons – entered Earth’s atmosphere above Arizona just before 4 a.m. local (MST) time. NASA estimates that the asteroid was moving at about 40,200 miles per hour (64,700 kilometers per hour).
Eyewitness reports placed the object at an altitude of 57 miles above the Tonto National Forest east of the town of Payson, moving almost due south. It was last seen at an altitude of 22 miles above that same forest.
“There are no reports of any damage or injuries—just a lot of light and few sonic booms,” said Bill Cooke in NASA’s Meteoroid Environment Office at the Marshall Space Flight Center in Huntsville, Alabama. “If Doppler radar is any indication, there are almost certainly meteorites scattered on the ground north of Tucson.”
The NASA Meteoroid Environments Office (MEO) monitors the small rock (meteoroid) environment near Earth in order to assess the risks posed to spacecraft by these bits of tiny space debris. As part of this effort, it operates a network of meteor cameras within the U.S. that are capable of detecting meteors brighter than the planet Jupiter. Three of these cameras are in southern Arizona.
Cooke notes that he and other meteor experts are having difficulty obtaining data on the June 2 fireball from meteor camera videos, since many of the cameras were almost completely saturated by the bright event.
Meteoroid impacts are a continuously occurring natural process. Every day, about 80 to 100 tons of material falls upon the Earth from space in the form of dust and meteorites. Over the past 20 years, U.S. government sensors have detected nearly 600 small asteroids, a few meters in size, which have entered the Earth’s atmosphere and created spectacular bolides. The superbolide that impacted over Chelyabinsk, Russia in 2013 is estimated to have been 65 feet (20 meters) in size and released over 40 times the energy of the Arizona fireball. Impacts of that size take place a few times a century, and impacts of larger asteroids are expected to be far less frequent (on the scale of centuries to millennia) but can happen on any day.
NASA’s Planetary Defense Coordination Office is responsible for finding, tracking, and characterizing near-Earth asteroids, identifying potentially hazardous objects, and planning for the mitigation of potential impacts to Earth that could do damage at ground level. More than 14,000 near-Earth asteroids (NEAs) have been discovered since NASA-sponsored efforts began in 1998 to detect, track and catalogue asteroids and comets.
Video obtained from the NASA meteor camera situated at the MMT Observatory on the site of the Fred Lawrence Whipple Observatory, located on Mount Hopkins, Arizona, in the Santa Rita Mountains. – Credit: NASA/MEO
This footage from the Sedona Red Rock Cam (part of the EarthCam network) shows how brightly the ground was illuminated during the fireball, which entered the atmosphere over Arizona shortly before 4 a.m. MST on June 2, 2016. – Credit: Sedona Red Rock Cam/EarthCam
This animation shows the orbit of the June 2, 2016 Arizona fireball and the view from its perspective as it approaches Earth. – Credit: NASA/MEO