Debris-sweeper of the Solar System


Jupiter as seen through HST's WF3. NASA, ESA, M.H. Wong (University of California, Berkeley), H.B. Hammel (Space Science Institute, Boulder, Colo.), A.A. Simon-Miller (Goddard Space Flight Center), and the Jupiter Impact Science Team.

By now, most people have heard that Jupiter got whacked earlier this month. The event was witnessed live by Anthony Wesley, an amateur astronomer living in Australia. Astronomers raced to observe the impact site to see if the debris plume could give them a clue to just what it was that hit the Jovian cloud tops. Among the telescopes trained on the site was Hubble Space Telescope and its Wide Field Camera 3. The results of that observation are in, and it seems that Jupiter was smacked by a giant meteor.  The image at left (on which you can click to massively enJovianate) shows where the meteor collided with the atmosphere on June 3 (the circle on the right-hand image). There’s no dark debris cloud as we’ve come to expect from other impact events.  This tells us that the meteor didn’t get very far into the clouds, since it didn’t explode and scatter dark debris around the region.

The flash of light recorded by Anthony Wesley during the event is created by the same type of activity that creates a “shooting star” in Earth’s atmosphere. The incoming object is moving at very high speeds and when it speeds into the atmosphere, a shock wave is generated by the resulting ram pressure. That shock wave heats the object to extremely high temperatures. That heats the atmospheric gases along the object’s path, and it also vaporizes a layer of the object’s surface. On Earth, what’s left of the object — if it makes it all the way through the atmosphere — falls to the ground as meteoritic material. On Jupiter, it just gets swallowed up by the clouds.

It used to be (back in the Shoemaker-Levy 9 days) that impacts into Jupiter were considered rare.  Not so much any more. We have 24/7 observations of the planets using vastly improved telescopes and sensors — and now, it turns out that Jupiter gets impacted by meteroids pretty frequently. Astronomers think this could be happening perhaps every few weeks or so.  We were lucky that someone was watching when this last one occurred, and I imagine that Jupiter-watchers will be keeping a close eye out for other impact events like this. Jupiter plays an important role in sweeping up debris in its path, and it very likely filtered out a lot of large debris early in solar system history — acting as a sort of protector for the inner planets. That means that Jupiter could have played a large role in shaping our solar system by lassooing many objects before they could whack into Mars, Earth, Venus, and Mercury.  If  so, and we didn’t have Jupiter, who knows what the inner solar system might look like now?  There’s no doubt that Jupiter has swept up much debris, but can it have other effects?

On the other hand, there is research supporting the idea that Jupiter’s presence might have increased the impact rate at Earth and the other planets over the history of the solar system (thanks to Daniel Fischer for reminding me of that research).  If that’s the case, you could still ask the same question:  if not for Jupiter, what would our solar system look like now — particularly the inner planets?  And, what role could Jupiter still be playing with the remaining solar system debris that still makes its way around the Sun in orbits that sometimes take it a little too close to Earth (and other worlds)  for comfort?  This is something that planetary scientists are seeking to understand as they map the orbits of solar system “stuff” and add what they find to their understanding of the complex mechanics of space debris and the worlds of the solar system.


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