No conspiracy here, JPL expert says of greenish meteor

As word spread of the greenish, glowing, fast-moving fireball streaking across the southwestern U.S. sky, speculation raged among conspiracy theorists and armchair astronomers.

Many took to social media Wednesday night with the theory that it was a spacecraft that suffered a SkyLab-style reentry.

Some said it was a piece of low-orbiting space junk. Others went to a far darker place: It was the opening volley of an alien invasion.

But experts say none of those scenarios is the most likely explanation. Instead, Don Yeomans, a Jet Propulsion Laboratory fellow who manages NASA’s Near Earth Object Program, said the celestial signs point to a broken chunk of “near-Earth asteroid” that became the equivalent of planetary road kill.

“We basically ran it over,” Yeomans said.

NASA officials checked for the possibility that the object was a wayward spacecraft or space junk but, for the most part, ruled those out, Yeomans said.

It’s not uncommon to look skyward on any given night and see streaking asteroid detritus. Wednesday night’s chunk was likely no bigger than a basketball and burned up in Earth’s atmosphere.

The heavenly phenomenon people saw across portions of Arizona, New Mexico and Southern California actually happens about twice a month around the globe, but most people don’t see it because it happens over an ocean or in sparsely populated areas. Seldom does anything less than 30 meters cause damage on the ground, although objects from space have been known to hit homes and other objects on earth.

“It’s sort of Mother Nature’s shot across the bow,” Yeoman said. “It’s an impressive light show, one of Mother Nature’s best.”

For some, the astronomy lesson wasn’t as exciting — or humorous — as the alternative.

“It can’t be a meteor!” PlanetFlipside tweeted. “Hovered for 15mins than 2nd appeared travelling horizontally.”

And mistercobi was convinced we had unearthly visitors, tweeting: “Another famous UFO sighting over so cal….government tries to play it off saying it was an asteroid.”

andrew.blankstein@latimes.com