Why Did Jupiter Flash?

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There’s something strange about last week’s Jupiter impact. There’s a chance it might not have been an ‘impact’ at all.

This twist in the amazing tale of the June 3 Jupiter “flash” comes after follow-up observations of the impact zone revealed nothing. It’s as if the impact never happened. There’s no debris, no turbulence and no black mark left in the atmosphere.

Observed by the very lucky Australian amateur astronomer Anthony Wesley (also the discoverer of the July 2009 Jupiter impact scar) and confirmed by Philippine amateur astronomer Christopher Go, last week’s event seemed to be an open-and-shut case. It was a bright fireball created when a comet or asteroid ploughed into the Jovian atmosphere. Simple.

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But as the 1994 impact of comet Shoemaker-Levy 9 and last year’s mystery impact “bruise” has shown us, when something big hits Jupiter, it leaves a big mess.

If you looked at the location of last week’s fireball, it’s as if nothing ever happened. So the obvious question being asked at the moment is: did anything hit Jupiter?

In today’s press release from NASA, the suggestion that Wesley and Go’s 2-second flash might have been an atmospheric phenomenon, some kind of mega-lightning bolt. But it’s a bit of a stretch.

“I consider that very, very unlikely,” says planetary scientist Glenn Orton of NASA’s Jet Propulsion Laboratory (JPL). “NASA spacecraft have seen lightning on Jupiter many times before, but only on the planet’s nightside. This dayside event would have to be unimaginably more powerful than any previous bolt we’ve seen. Even Jupiter doesn’t produce lightning that big.”

So could it have been some kind of atmospheric anomaly on Earth that just happened to occur in the line of sight of Jupiter’s disk? That’s even more unlikely as Wesley and Go observed the same event, but at different locations on the planet, spaced thousands of kilometers apart.

That means we have to circle back and reconsider that it was an impact, but for some reason Jupiter has “covered up” any residue of the massive fireball.

One idea posited by NASA scientists is that the impact happened at the same latitude as one of Jupiter’s recently disappeared atmospheric stripes. The South Equatorial Belt (SEB) has inexplicably vanished, possibly getting shrouded in a planet-wide cloud of high-altitude ammonia cloud. Could the same cloud be shrouding the site of last week’s impact?

Orton is skeptical, any fireball produced by a speeding chunk of ice or rock would have burnt up high above the cirrus, leaving some kind of disturbance high in the atmosphere.

So there’s only one likely possibility: The fireball was caused by some kind of impactor, but the object was big enough to generate an energetic flash to be seen from Earth, yet small enough not to leave any visible scarring.

Watch this space, it seems likely that this little mystery will keep astronomers busy for some time to come.

Photo credit: Anthony Wesley