Telescopes Follow Mystery Jupiter Spot

July 22, 2009

 

Since I last reported on the strange spot that suddenly appeared on Jupiter last Sunday, it has been the “splat” or rather “splash” seen ‘round the world. 

An unknown interplanetary object did a “cannonball” by plunging into Jupiter’s atmosphere, disintegrating, and splashing debris above the cloud tops.

There was a sense of “déjà vu all over again” about this because it was exactly 15 years ago that I reported on a day-by-day basis the sequential impacts of over 20 fragments of comet Shoemaker Levy 9 that carpet-bombed Jupiter. A belt of dark bruise-looking features grew in the atmosphere following each subsequent impact.

This week professional and amateur telescopes around the world have been intently trained on the blot smearing across Jupiter’s cloud tops much like the SL9 features.

There has been a lot of discussion on this blog about the drama happening 360 million miles away. Here’s a quick list of answers based on what has been observed and conjectured so far:

How do we know it’s a collision?

The shape and smearing of the spot is very similar to what happened during the SL9 impacts. It has expanded to the twice the width of the continental United States. Infrared observations of the spot have found a warming of the upper atmosphere with possible abundance of ammonia. This might have been dredged up from lower altitudes by the impact.

How big was the object?

Based on the physical diameter of the SL9 debris plumes shortly after impact, this impactor was not much larger than the length of several football fields. I'm bemused that some comments here speculate that it was an unknown planet or brown dwarf. These objects are vastly too big to be roaming around the solar system.

Was it a comet or asteroid?

The impactor was probably a comet because comets have Jupiter-crossing orbits. Asteroids generally don't. It’s a small distinction because asteroids and comets are all debris from the protostellar nebula that formed the sun and planets. Comets simply contain much more ice.

How frequently does this happen?

Good guess. Estimates for something of this size are an impact once every 30 years. The smaller the impactor, the more frequent the collisions.  However there are no recorded black spots on Jupiter prior to the SL9 event.  We also have more telescopes and sky observers today, so these events may suddenly be getting more easily recognizable.

What would have happened if the comet hit Earth instead?

If it hit Earth with the same velocity, the explosion would have been thousands of time more powerful than the suspected comet the exploded over the Tunguska River Valley in Siberia in 1908. The devastation would have been much wider. The 1908 explosion packed enough energy to level a city the size of Washington D.C. and suburbs.

Why wasn’t the impactor detected?

The comet SL9 was seen because it broke up into a string of pieces and went into an elliptical orbit about Jupiter. But a lone intruder, which is what this seems to be, would be much harder to detect at Jupiter’s distance.

Stay tuned! More observations to come.