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Surprise scar that appeared on Jupiter last year looks to have been an asteroid impact

The views expressed are those of the author and are not necessarily those of Scientific American.


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Jupiter impact scar following July 2009 collisionWhen a mystery object smacked into Jupiter without warning in July 2009, an event whose aftermath was first spotted by an amateur astronomer in Australia, observers across the globe scrambled to get a look at the planet to figure out just what had happened.

Astronomers working on other campaigns at world-class observatories, including one of the 10-meter Keck telescopes in Hawaii, swung into action, training their borrowed instruments on Jupiter to photograph the after-effects of the collision. Some of the most striking images, so to speak, came from the Hubble Space Telescope, which had only recently been upgraded by visiting astronauts and was still undergoing checkout of some of its new components.

Heidi Hammel, a senior research scientist at the Space Science Institute in Boulder, Colo., was part of the team commandeering Hubble to view the aftermath, as she had been 15 years earlier for the collision into Jupiter of the comet Shoemaker–Levy 9. She and her colleagues published the results of their new observations, and the ways in which the 2009 impact differed from that of Shoemaker–Levy 9 in 1994, in the June 1 issue of the Astrophysical Journal Letters.

Assuming that similar atmospheric processes were in play for Shoemaker–Levy 9 and the 2009 event, Hammel says, the dark bruise (near the bottom of the photo above) observed by Hubble after the more recent impact was essentially a debris field stirred up by a roughly 500-meter body. "A plume of material was blasted out of the atmosphere that then collapsed down onto the tops of the clouds," she says. "I think of all that black stuff as Jovian soot." Watching how that bruise evolved and faded over time, Hammel’s group has found that the surprise impactor was more than likely an asteroid, not a comet.

When Shoemaker–Levy 9 struck in 1994, the comet punched into Jupiter in a series of fragments arriving over the course of a week, but the 2009 impactor seems to have held together under the intense gravitational strain from the massive planet, as only a single bruise was observed. "That suggests that it had some strength to it," Hammel says, which seems a better fit with a solid asteroid than a cometary rubble pile.

In addition, the Shoemaker–Levy 9 impact sites were surrounded by fuzzy halos visible in the ultraviolet, attributed to the debris clouds surrounding the nuclei of the comet fragments. But the impact scar of 2009 did not have such a halo. Finally, Hubble’s ultraviolet imagery showed that the 2009 bruise faded much more quickly than the marks left by the 1994 comet strike. "That suggests that maybe there weren’t as many small particles," Hammel says. "It’s really sort of controversial; we’ve been debating this amongst ourselves."

Another group, which also reported its findings in the June 1 issue of the Astrophysical Journal Letters, ran simulations of the impactor’s orbit, tracing it backward in time to try to uncover its provenance. But the team, which was led by Agustín Sánchez-Lavega of the University of the Basque Country in Bilbao, Spain, and also included Anthony Wesley, the Australian amateur astronomer who discovered the impact, found a roughly equal probability for the mystery object originating from the asteroid belt or a cometary reservoir.

Not having seen the object prior to impact, the two groups were forced to do a bit of detective work to infer the most likely scenario for what happened. "When you take every one of these bits and pieces together, you start to get a story," Hammel says. "But we’re trying to be very clear that we don’t have a smoking gun to prove that it was definitely an asteroid and not a comet."

Photo credit: NASA, ESA, H. Hammel (Space Science Institute, Boulder, Colo.), and the Jupiter Impact Team

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  1. 1. jtdwyer 1:38 pm 06/4/2010

    The article states:
    Assuming that similar atmospheric processes were in play for Shoemaker-Levy 9 and the 2009 event, Hammel says, the dark bruise (near the bottom of the photo above) observed by Hubble after the more recent impact was essentially a debris field stirred up by a roughly 500-meter body. "A plume of material was blasted out of the atmosphere that then collapsed down onto the tops of the clouds," she says. "I think of all that black stuff as Jovian soot." Watching how that bruise evolved and faded over time, Hammel’s group has found that the surprise impactor was more than likely an asteroid, not a comet.

    I’d think the black stuff is not Jovian soot but more likely asteroid soot produced by its incineration in the dense Jovian atmosphere…

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  2. 2. doug l 2:41 pm 06/4/2010

    The ever growing gorilla in the room is the increasing realisation that impacts from cosmic bollides and other objects travelling through our neighborhood, are more common than our measurements previously have lent us to believe. While untold amounts of ink and anxiety is spent over a few inches or feet of sea level rise, the occasional quake generated tsunami, or a slight increase in overall temps which for all we know with any certainty might be just natural for the most part, they will look like a walk in the park should even a moderately sized impact make the planet ring especially when we consider how tenuous our infrastructures are for our civilization.
    Ironically, back in the 60s if we had taken the direction of the great designers of what were to be our first generation of space ships; Von Braun and Truax, we’d already be inhabiting permanent space stations, exploring the local planets and learning how to address these game changing impactors. Instead we took up ‘the race to the moon’ so we used the military’s rockets, which thankfully we had and which thankfully worked, but the consigned us to a system of launching payloads that all but guaranteed that space would forever be complex, dangerous and woefully expensive.
    As we enter a new era in space development and unleash the power of innovation that commercial development possesses; a quality all but unknown in the quasi-military/academic era of space exploration through which we are now passing, we will see the cost of launching drop, payload sizes become appropriately scaled (much MUCH bigger), and find that we no longer have to send swiss watch scaled probes that sip propellant like it cost a million dollars a gallon…which incidentally it does when you send it up in a man rated ballistic missile.
    Asteroid/impactor detection and interception is only one of the many benefits from a new and re-vitalized space development program. I’d love to see the US at the forefront, and with the latest changes that have been made and the shift away from NASA’s culture or cost over-runs, military control, and small steps if any steps at all, we or somebody will finally discover that once we get out of this confounded gravity well called earth we’ll be halfway to anywhere and travelling through space where energy and resources are plentiful for those who know how to harness them AND stay like we mean it.

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  3. 3. jtdwyer 12:50 am 06/5/2010

    doug l – I’m still more concerned about increasing overpopulation, depletion of nutrients and the resulting environmental impacts.

    I’m afraid humanity can’t survive long enough on the perfect Earth to develop the ability for a viable reproducing population to independently survive on any alternate, inhospitable planet.

    Even if we could that would only aid a select few, abandoning generations of billions of humans to untold suffering and death.

    I think minimizing human suffering for our progeny is our only reasonable direction for our developmental efforts. Rockets are cool, though.

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  4. 4. jgrosay 6:09 pm 06/11/2010

    The one who put Jupiter there did a good job (Contrarily to the thoughts of Auguste Comte, that wrote "it’s obvious that the solar system is badly designed"), otherwise such rolling stones would have had a greater probability of hitting planet Earth

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