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A New Jovian Impact

It’s a lively Solar System indeed. In yet another confirmation of the value of amateur astronomy, Australia’s Anthony Wesley tipped off scientists on July 19 that a new object had struck Jupiter and observatories around the world zeroed in on the event. It comes exactly fifteen years after the ‘string of pearls’ comet Shoemaker-Levy 9 struck the giant planet. Infrared images show a likely impact point near the south polar region, visible in the image below.


Image: A large impact shown on the bottom left on Jupiter’s south polar region captured on July 20, 2009, by NASA’s Infrared Telescope Facility in Mauna Kea, Hawaii. Image credit: NASA/JPL/Infrared Telescope Facility.

Unlike Shoemaker-Levy 9, this event may have been caused by a single object. UC Berkeley and SETI Institute astronomer Franck Marchis explains:

“The analysis of the shape and brightness of the feature will help in determining the energy and the origin of the impactor. We don’t see other bright features along the same latitude, so this was most likely the result of a single asteroid, not a chain of fragments like for SL9.”

It’s entertaining to note that UC Berkeley astronomer Paul Kalas, in Greece at the time, decided to use scheduled observing time on the Keck II telescope in Hawaii to investigate the Jupiter strike because he read about it on Marchis’ blog. So we have the astronomy world lit up by an Australian amateur making a find that’s quickly disseminated through various channels including weblogs, triggering quick and intense observing sessions with instruments worldwide. Hubble’s Wide Field Camera 3 will soon be on the case as well with visible and ultraviolet observations.

A planetary scar the size of the Pacific Ocean gets the attention, and should remind us, as did Shoemaker-Levy 9, that although the days of the Late Heavy Bombardment are long gone, there are objects wandering around the system that could end our civilization. The need for a mission to a near-Earth object to learn more about these impactors should be apparent, and it’s a technology driver for later deep space missions as well.


Comments on this entry are closed.

  • Doug M. July 22, 2009, 10:33

    Of course, impacts on Jupiter are going to be much more common. Based on surface area alone, you’d expect Jupiter to get hit more than 100 times more often. When you add in the fact that Jupiter’s massive gravity sweeps across an immensely greater volume of space… well, someone must have run the numbers, but I’d reasonably expect impacts to be at least 1,000 times more common than on Earth, a

    Also, impacts on Jupiter will be much more severe. Jupiter’s escape velocity is more than five times ours! Anything falling down that immense gravity well is going to hit with tremendous force.

    This is slightly offset by the fact that things tend to move a bit faster down here in the inner Solar System, but still — a typical piece of asteroidal junk is going to hit Jupiter 2-3 times as fast as it would hit us, producing a lot more kinetic energy.

    Doug M.

  • Parmanello July 22, 2009, 15:53

    Be that as it may Chief, it’s pretty sobering that an A-roid large enough to leave an Earth sized scar on old Zeus could totally avoid detection. It goes to show how little coverage we have of the sky, let alone ability to take these things out.

    I don’t know about you gentlemen but I’m already bulk buying tinned ham and powdered eggs for when Apophis comes a knocking.

  • Mark July 23, 2009, 0:03

    Is there anything new to be learned from the claim that this happened exactly fifteen years after the last known impact? Some heretofore unknown 15-year periodicity of orbital mechanics within the solar system that would bring Jupiter across the path of some asteroids or comets, similar to our Leonid meteor showers here on Earth?

    Or could this simply be the beginning of the conversion of Jupiter into our second sun, as happened in the movie 2010? Has Hubble detected any monoliths orbiting in or near the Jovian system?

  • Doug M. July 23, 2009, 3:24

    Umm. The current estimate of the impactor’s size is under a kilometer across. There are billions of rocks that size in the Solar System, and we haven’t detected or tracked one percent of them. This isn’t something to get the vapors about.

    By way of comparison, Shoemaker-Levy was about 10 times this size, and it was spotted a year before it hit Jupiter.

    Impact energy has been estimated as ~~10 gigatons. However, the same rock hitting Earth would have struck with about 1/10 as much energy — “only” 1 gigaton. This would certainly be unpleasant if you were anywhere in the neighborhood. However, volcanic explosions this big occur naturally every thousand years or so; Krakatoa, back in 1883, was about 200 megatons or 1/5 a gigaton, and Tambora may have approached a gigaton. An impact this size on Earth would kill anything within 100 km, and would probably alter the climate planetwide for a couple of years. But it wouldn’t end civilization, never mind trigger a mass extinction or such.

    Also, the scar’s size seems to have been a couple thousand km across:


    continent sized, not Earth-sized.

    Doug M.

  • NS July 23, 2009, 3:41

    A little OT, but here’s a link for a proposed mission to Apophis (requires Quicktime player):


  • Parmanello July 25, 2009, 9:15

    How did you calculate the impact energy? Why would it be an order of magnitude higher if you said the velocity was 2 – 3 times more for Jupiter than Earth? (Surely that means 4 to 9 times)

    A gigaton is some 20 Tsara bombas equivalent, which would be utterly devastating for sure, but I agree not civilization threatening (unless…no, no I won’t go there).

    I agree also that there are many other untracked asteroids, I was being a little facetious in my original comment so I apologise for that.

    Best regards

  • ljk July 27, 2009, 0:18

    Sunday, July 26, 2009

    Project Icarus: an alternate history

    By David S. F. Portree – Robot Explorers blog

    A couple of weeks ago, I wrote on this blog about an 1967 MIT study called Project Icarus. The study, performed by MIT students as an exercise in systems engineering, assumed that the mile-wide asteroid Icarus would not merely pass Earth at a distance of four million miles on June 19, 1968, but would instead strike in the Atlantic Ocean east of Bermuda. The resulting big splash would have inundated ocean-front property around the world.

    I’ve been thinking about this as a point of departure for an alternate history. What if Icarus actually had been found in early 1967 to be 18 months from a collision with Earth? And, what if the U.S. – probably the only human agency at the time capable of intervening – had made every effort to destroy and/or deflect it?

    Full alternate reality here:


  • ljk July 28, 2009, 15:36

    If you want to see the Jovian impact of July 19 for yourself while it
    remains in the planet’s atmosphere, see here:


  • ljk July 31, 2009, 17:28


    Hubble View: Jupiter Impact

    Credit: NASA, ESA, H. Hammel (Space Science Institute, Boulder, Co.), and the Jupiter Impact Team

    Explanation: This sprawling dark marking is Jupiter’s latest impact scar, a debris plume created as a small asteroid or comet disintegrated after plunging into the gas giant’s atmosphere. Located in Jupiter’s south polar region, the new feature was discovered by Australian amateur astronomer Anthony Wesley on July 19.

    On July 23rd Wesley’s discovery was followed up by the Hubble Space Telescope with its newly installed Wide Field Camera 3, creating this sharpest view of the evolving debris plume.

    Estimates indicate that the impacting object itself was several hundred meters across. Similar impact markings were created when pieces of Comet Shoemaker-Levy 9 slammed into Jupiter’s cloud bands in July of 1994.

  • ljk August 9, 2009, 23:54

    Galileo dust data from the jovian system: 2000 to 2003

    Authors: Harald Krueger, D. Bindschadler, S. F. Dermott, A. L. Graps, E. Gruen, B. A. Gustafson, D. P. Hamilton, M. S. Hanner, M. Horanyi, J. Kissel, D. Linkert, G. Linkert, I. Mann, J. A. M. McDonnell, R. Moissl, G. E. Morfill, C. Polanskey, M. Roy, G. Schwehm, R. Srama

    (Submitted on 7 Aug 2009)

    Abstract: The Galileo spacecraft was orbiting Jupiter between Dec 1995 and Sep 2003. The Galileo dust detector monitored the jovian dust environment between about 2 and 370 R_J (jovian radius R_J = 71492 km). We present data from the Galileo dust instrument for the period January 2000 to September 2003.

    We report on the data of 5389 particles measured between 2000 and the end of the mission in 2003. The majority of the 21250 particles for which the full set of measured impact parameters (impact time, impact direction, charge rise times, charge amplitudes, etc.) was transmitted to Earth were tiny grains (about 10 nm in radius), most of them originating from Jupiter’s innermost Galilean moon Io. Their impact rates frequently exceeded 10 min^-1.

    Surprisingly large impact rates up to 100 min^-1 occurred in Aug/Sep 2000 when Galileo was at about 280 R_J from Jupiter. This peak in dust emission appears to coincide with strong changes in the release of neutral gas from the Io torus. Strong variability in the Io dust flux was measured on timescales of days to weeks, indicating large variations in the dust release from Io or the Io torus or both on such short timescales.

    Galileo has detected a large number of bigger micron-sized particles mostly in the region between the Galilean moons. A surprisingly large number of such bigger grains was measured in March 2003 within a 4-day interval when Galileo was outside Jupiter’s magnetosphere at approximately 350 R_J jovicentric distance.

    Two passages of Jupiter’s gossamer rings in 2002 and 2003 provided the first actual comparison of in-situ dust data from a planetary ring with the results inferred from inverting optical images.

    Comments: 59 pages, 13 figures, 6 tables, submitted to Planetary and Space Science

    Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

    Cite as: arXiv:0908.1051v1 [astro-ph.EP]

    Submission history

    From: Harald Krueger [view email]

    [v1] Fri, 7 Aug 2009 13:30:17 GMT (2499kb,D)


  • ljk September 8, 2009, 9:31


    Unexpected Impact on Jupiter

    Credit: ALPO, Theo Ramakers

    Explanation: Two months ago, something unexpected hit Jupiter. First discovered by an amateur astronomer Anthony Wesley on 2009 July 19, the impact was quickly confirmed and even imaged by the Hubble Space Telescope the very next day. Many of the world’s telescopes then zoomed in on our Solar System’s largest planet to see the result. Some of these images have been complied into the above animation.

    Over the course of the last month and a half, the above time-lapse sequence shows the dark spot — first created when Jupiter was struck — deforming and dissipating as Jupiter’s clouds churned and Jupiter rotated. It is now thought that a small comet — perhaps less than one kilometer across — impacted Jupiter on or before 2009 July 19.

    Although initially expected to be visible for only a week, astronomers continue to track atmospheric remnants of the impact for new information about winds and currents in Jupiter’s thick atmosphere.

  • ljk September 15, 2009, 10:19

    September 13, 2009

    Jupiter Captured Comet as Temporary Moon

    Written by Nancy Atkinson

    Jupiter’s gravity well has been known to capture objects – evidenced by the recent impact on the gas giant discovered by amateur astronomer Anthony Wesley. But one object captured by Jupiter in the mid 1900’s was later able to escape from the planet’s clutches. Researchers have found comet 147P/Kushida-Muramatsu was captured as a temporary moon of Jupiter, and remained trapped in an irregular orbit for about twelve years.

    “Our results demonstrate some of the routes taken by cometary bodies through interplanetary space that can allow them either to enter or to escape situations where they are in orbit around the planet Jupiter,” said team member Dr. David Archer.

    With this discovery, five such objects have now been discovered where the phenomenon of temporary satellite capture (TSC) has occurred, but this new research suggests it might happen more frequently than was expected. Kushida-Muramatsu orbited Jupiter between 1949 and 1961, the third longest capture period of the five objects.

    Full article here: