From the ABC 7 Weather team

A huge comet nearly obliterated the Earth in 1883?

October 19, 2011 - 05:00 AM
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Something really big whizzing through space almost wiped out the human race in the 19th century, according to a study by Mexican astrophysicists.

A large comet may have missed hitting Earth by as little as the distance from D.C. to Boston, say Mexican scientists in a new study. Pictured: An artist's impression of Comet Temple 1, the target of the 2005 Deep Impact mission. (NASA)

It sounds like a Michael Bay spectacular: Not content with merely wiping out the dinosaurs, the coldly calculating forces of the universe made a death play for humanity by sending a comet on a kamikaze mission to Earth.

As the cheer-killing ice ball neared the planet, chunks broke off that measured four times the size of the Louisiana Superdome's roof. The jagged shards whistled so close that pedestrians walking below practically felt the wind rustling in their hair. The distance of the comet's miss was as short as 334 miles, less than the car ride from D.C. to Boston.

Great movie, right? Well, astrophysicists from the Universidad Nacional Autónoma de Méxicoas think that it actually happened. In a new paper, the scientists claim that this assault by cosmic shards was observed, if not totally understood, by Mexican astronomer Jose A. y Bonilla on August 12 and 13, 1883. Other astronomers, however, think that Bonilla might've just been seeing geese. Skip to the end for an opposing viewpoint.

This much is known: On those two days, while peering up at space from his observatory in central Mexico, Bonilla noted a fleet of strange objects passing across the Sun's blazing disc. They were shrouded in mist and dragged trails of fog behind them. In front of the sun they looked dark; against the background of space they glowed.

Bonilla logged a total of 447 such objects during his observation. In 1886, he published his notes in L'Astronomie magazine, leaving out an explanation for the phenomenon. That lack of a hypothesis bugged the publication's editor, who concluded that the UFOs were either insects, birds or dust that had passed over the careless Bonilla's telescope. Case closed.

Until this week. The authors of the Mexican study give Bonilla a little more credit than the deceased French editor. After analyzing his findings, they have decided that the smoking objects belonged to the nucleus of a comet that had become fragmented, a not uncommon occurrence for these lonely wanderers of space. The size of the fragments suggested that the original comet had a mass that exceeded that of Halley's Comet – perhaps a billion tons or more. And the angle at which Bonilla saw them indicated that they had barely passed up a catastrophic caress with Earth.

There were two comets that astronomers observed in 1883, Brooks-Swift and Pons-Brooks, and the paper notes that either one could be responsible for unleashing the debris swarm that supposedly buzzed Earth. Had the path of the comet changed ever so slightly, the scientists say, "we would have had 3,275 Tunguska events in two days, probably an extinction event." Tunguska was a humongous explosion in Siberia in 1908 that was probably caused by an asteroid impact; the detonation was so powerful that people 40 miles away felt like they were burning.

How believable is this scary theory? Also like a Michael Bay movie, there are a couple of annoying plot holes, like the fact that nobody but Bonilla seemed to notice these hundreds of sun-obscuring objects. Also, comets that travel close to Earth tend to spray meteorites all over the place, and there were no widespread reports of shooting stars during those two days in August.

For an unflinching dissection of this homicidal comet theory, rocket on over to Phil Plait's entertaining post at Bad Astronomy.

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