Jupiter Got Whacked by Yet Another Asteroid/Comet!

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Source:  By Phil Plait, Bad Astronomy

2016-03-29. Jupiter Got Whacked by Yet Another Asteroid/Comet! By Phil Plait, Bad Astronomy. For GSS A Changing Cosmos chapter 1. Excerpt: On March 17, Gerrit Kernbauer, an amateur astronomer in Mödling, Austria, was taking video of Jupiter using a 20 cm telescope. ...he got more than he expected. At 00:18:33 UTC he captured what looks very much like the impact of a small comet or asteroid into Jupiter! [see video] ...On average ...an object will hit Jupiter with roughly five times the velocity it hits Earth, so the impact energy is 25 times as high. The asteroid that burned up over Chelyabinsk, Russia, in 2013 was 19 meters across, and it exploded with the energy of 500,000 tons of TNT. Now multiply that by 25, and you can see how it doesn’t take all that big a rock to hit Jupiter for us to be able to see it from Earth. Incidentally, at these huge speeds, hitting the atmosphere is like slamming into a wall. A lot of people get understandably confused how an asteroid can explode due to air, but the pressures involved ...are ridiculously huge. The air and rock heat up, the rock starts to fall apart, and each chunk then gets hot, and so on, creating a very rapid cascade that releases the energy of motion in just a second or two. Bang. Very, very big bang. Jupiter gets hit a lot. ...The most famous is the string of impacts from the comet Shoemaker-Levy 9 in 1994, which hammered the planet over and again as the comet, broken into a dozen separate pieces by Jupiter’s gravity, slammed into the planet and exploded. In 2009 something relatively big hit the planet (and Hubble caught the aftermath). It was hit again in June 2010 (with a cool color photo this time), and then again in August 2010. A repeat performance was held in September 2012. ...Looking over these observations, it seems that on average Jupiter gets hit by something big enough to see from Earth about once per year. Mind you, we miss ones that happen on the far side of the planet, or when Jupiter is too close to the Sun to be observed....   [Here are observed impacts over the past couple decades on Jupiter:]
16-22 July 1994  [P/SL-9 20+ fragments]
19 July 2009 [Anthony Wesley]
3 June 2010 [Anthony Wesley & Christopher Go]
20 Aug 2010 [Masayuki Tachikawa]
10 Sept 2012 [Dan Petersen]
17 Mar 2016

http://www.slate.com/blogs/bad_astronomy/2016/03/29/jupiter_hit_by_asteroid_or_comet_in_march_2016.html

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