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Jupiter Impacts Add Up

These days we think of Giovanni Cassini in relation to Saturn, for obvious reasons, but the Italian astronomer (1625-1712) did a lot more than discovering the division in the rings of Saturn that would later bear his name. In addition to his studies of the Saturnian moons, Cassini shares credit for the discovery of Jupiter’s Great Red Spot, and in conjunction with Jean Richer, made parallax observations of Mars that allowed its distance to be determined in 1672.

But back to Jupiter, for in 1686 Cassini reported seeing a dark spot on the planet, one that from his description was roughly the size of the largest impact made by the Comet P/Shoemaker-Levy comet fragments in 1994. We’re dealing with crude telescopes and lack of corroborating information with Cassini’s observation, but Shoemaker-Levy left us with Hubble imagery when it struck the giant planet after breaking apart into more than twenty pieces enroute.

I mention Cassini’s early sighting because it’s possible he was also seeing the results of an impact, and that would be significant. Given what we know about asteroid and cometary impacts, the assumption has been that impacts with Jupiter should occur on a timescale of every few hundred to few thousand years. But they’re starting to mount up. Add to Cassini’s possible impact sighting an 1834 observation by the British astronomer George Airy, who reported a dark feature that was four times as large as the shadows cast by the Galilean moons.

And now, just sixteen years after Shoemaker-Levy, we have two more impacts, the first evidently the result of an asteroid rather than a comet. The differences between it and Shoemaker-Levy are instructive. The impact occurred on July 19, 2009, was spotted by Australian amateur Anthony Wesley and quickly followed up by observatories around the world and via the Hubble telescope. The impact site was elongated, indicating an object that descended at a shallower angle than the Shoemaker-Levy fragments, and a different direction of origin.

Image: Hubble image of Jupiter’s full disk taken July 23, 2009, revealing an elongated, dark spot at lower, right (inside the rectangular box). The photograph was taken four days after an amateur astronomer first spotted the scar. The unexpected blemish was created when an unknown object plunged into Jupiter and exploded, scattering debris into the giant planet’s cloud tops. The series of close-up images at right, taken between July 23, 2009 and Nov. 3, 2009, show the impact site rapidly disappearing. Jupiter’s winds also are spreading the debris into intricate swirls. Credit: NASA, ESA, M.H. Wong (University of California, Berkeley), H. B. Hammel (Space Science Institute, Boulder, Colo.), I. de Pater (University of California, Berkeley), and the Jupiter Impact Team.

Also telling is that while the 1994 impact showed a distinct halo around the site, evidently the result of fine dust rising from the cometary material, the 2009 impact showed no halo and left little contrast between the debris and Jupiter’s clouds. Scientists are interpreting this as evidence of a lack of lightweight particles, pointing to a solid impactor like an asteroid rather than a comet.

Wesley and fellow amateur Christopher Go, based in the Philippines, also lay claim to a June 3 impact this year, an event first noted by Wesley and confirmed by Go. Both caught the impact on video. This Ars Technica story has more, and a detailed breakdown of the events is offered in Emily Lakdawalla’s account for the Planetary Society. Follow-up observations may yield more information, but for now this video, with its one-second flash, makes it clear that Jupiter has pulled in another victim.

We can’t with certainty ascribe the 1686 and 1834 observations to impacts, but the fact that we now have three Jupiter strikes within fifteen years does raise the eyebrows. The 2009 impactor is thought to have been about 500 meters wide, probably having its origin in the Hilda family of asteroids that orbit near Jupiter. It’s chastening to hear that its strike created an event that was the equivalent of several thousand nuclear bombs exploding. Not as big as the largest Shoemaker-Levy impacts, but that fact in itself tells us that while Jupiter may do a good job cleaning out our system’s inner debris, one stray asteroid could do unthinkable damage on our planet’s surface.

The paper is Sánchez-Lavega et al., “The Impact of a Large Object on Jupiter in July 2009,” Astrophysical Journal Letters 715 (June, 2010), L155 (abstract). More on the 2010 impact as the investigation proceeds.


Comments on this entry are closed.

  • Daniel Fischer June 6, 2010, 19:11

    According to a big study done in 1994 all of the historical ‘dark spot’ sightings on Jupiter are probably just Jovian meteorology (which can produce amazing things at times); I just talked to that paper’s author and he stands by his conclusions.

  • Tristram Brelstaff June 7, 2010, 2:30

    The two impacts a year apart might not be independent: they could conceivably be two components of the same binary asteroid that was was disrupted by close approaches to Jupiter.

  • Carl June 7, 2010, 21:49

    Jupiter’s environment has likely made for very different evolutions of Ganymede and Callisto http://news.sciencemag.org/sciencenow/2010/01/25-02.html

    Reasonably, the density and occurrence of fragmentary incursions increases with proximity to Jupiter. The above article surmises Ganymede would have received twice the impacts of its outer neighbor during the Late Heavy Bombardment.

    Should one or both stars in the Centauri system harbor rocky planets, they would exist without the benefit of a jovian. Planetary developments would have been different without the influence of a massive primary world. “Pandora” might get more showers of meteors and comet fragments…

  • Adam June 8, 2010, 3:53

    Hi Daniel

    The Dark Spots seem associated with impacts – kind of seems the burden of proof has shifted back to holders of the null hypothesis. No way of knowing either way now, of course.

  • Mike June 8, 2010, 10:38

    Regarding Carl’s suggestion that any planets in the Alpha Centauri AB system would be bereft of the protection that Jupiter gives us here on Earth.
    In a binary system like Alpha Centauri each star would provide the same protective effect for any planets in the other star’s inner system. This effect is much more pronounced there and might have seriously reduced the amount of volatiles,like water,that could have been delivered by comets to any newly formed planets there, as this is considered how the inner rocky planets in our system may have received their lighter elements.

  • Carl June 8, 2010, 18:35

    Hi, Mike,

    Didn’t think of that. In our system, the sun should pull in much more than its largest world. Jupiter is a spoiler of sorts in this regard… a local disturbance, as it were.

    Around other stars, other variables will also include the populations of remote system Oort clouds and/or Kuiper Belts.

    If future telescope engineering, from huge interferometers to gravity lensing enables us to study nearer exoplanets, observations will help unveil individual planetary histories. If there are Centauri exoplanets, they would receive a lot of attention.

  • ljk September 9, 2010, 22:54
  • ljk September 14, 2010, 7:06

    First Earth-based Detection of a Superbolide on Jupiter

    Authors: R. Hueso, A. Wesley, C. Go, S. Perez-Hoyos, M. H. Wong, L. N. Fletcher, A. Sanchez-Lavega, M. B. E. Boslough, I. de Pater, G. S. Orton, A. A. Simon-Miller, S. G. Djorgovski, M. L. Edwards, H. B. Hammel, J. T. Clarke, K. S. Noll, P. A. Yanamandra-Fisher

    (Submitted on 9 Sep 2010)

    Abstract: Cosmic collisions on planets cause detectable optical flashes that range from terrestrial shooting stars to bright fireballs. On June 3, 2010 a bolide in Jupiter’s atmosphere was simultaneously observed from the Earth by two amateur astronomers observing Jupiter in red and blue wavelengths. The bolide appeared as a flash of 2 s duration in video recording data of the planet.

    The analysis of the light curve of the observations results in an estimated energy of the impact of 0.9-4.0×10^{15} J which corresponds to a colliding body of 8-13 m diameter assuming a mean density of 2 g cm^{-3}.

    Images acquired a few days later by the Hubble Space Telescope and other large ground-based facilities did not show any signature of aerosol debris, temperature or chemical composition anomaly, confirming that the body was small and destroyed in Jupiter’s upper atmosphere. Several collisions of this size may happen on Jupiter on a yearly basis.

    A systematic study of the impact rate and size of these bolides can enable an empirical determination of the flux of meteoroids in Jupiter with implications for the populations of small bodies in the outer Solar System and may allow a better quantification of the threat of impacting bodies to Earth. The serendipitous recording of this optical flash opens a new window in the observation of Jupiter with small telescopes.

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

    Journal reference: The Astrophysical Journal Letters, 721, L129 (2010)

    DOI: 10.1088/2041-8205/721/2/L129

    Cite as: arXiv:1009.1824v1 [astro-ph.EP]

    Submission history

    From: Ricardo Hueso [view email]

    [v1] Thu, 9 Sep 2010 16:55:22 GMT (318kb)