Asteroid collides with Jupiter (July two years ago)

Click on image to enlarge: Infrared images of Jupiter on July 20, 2009 (left) and August 16, 2009 from NASA's Infrared Telescope Facility in Mauna Kea, Hawaii. Particle debris at bottom left. (Credit: NASA/IRTF/JPL-Caltech/University of Oxford.)

Two papers in the January issue of Icarus (vol 211) conclude that the wide debris scatter in the atmosphere of Jupiter captured by NASA’s infrared telescope in Hawaii resulted from an impact by an asteroid. The papers are: G.S. Orton, et al., “The atmospheric influence, size and possible asteroidal nature of the July 2009 Jupiter impactor” (pp 587-602) and Leigh N. Fletcher, et al., “The aftermath of the July 2009 impact on Jupiter: Ammonia, temperatures and particulates from Gemini thermal infrared spectroscopy” (pp 568-586). Fletcher is with the Jet Propulsion Laboratory at the California Institute of Technology and Orton is with the Department of Atmospheric, Oceanic & Planetary Physics, at Oxford University’s Clarendon Laboratory.

The impact took place on July 19, 2009. The first photograph was taken the next day. The international group of researchers analyzed the direction and mass of the trajectories of the ejected debris, the temperature of the area around the impact, the spectra of the aerosols from the impact. The impact increased the temperature of a vast region by 3 to 4 Kelvin at about 42 kilometers above its cloud. The spectra of the debris was consistent with amorphous iron and magnesium-rich silicates and silicas. The researchers concluded that the impact was from an asteroid rather than a comet, like Shoemaker-Levy 9, the only other major impact event observed on Jupiter (in July 1994).

The Jet Propulsion Labratory’s press release concerning the papers quotes Fletcher:

“Comparisons between the 2009 images and the Shoemaker-Levy 9 results are beginning to show intriguing differences between the kinds of objects that hit Jupiter. The dark debris, the heated atmosphere and upwelling of ammonia were similar for this impact and Shoemaker-Levy, but the debris plume in this case didn’t reach such high altitudes, didn’t heat the high stratosphere, and contained signatures for hydrocarbons, silicates and silicas that weren’t seen before. The presence of hydrocarbons, and the absence of carbon monoxide, provide strong evidence for a water-depleted impactor in 2009.”

The impact was first noticed as an unusual scar on the planet by an amateur astronomer, Anthony Wesley of Australia, who notified Orton, who in turn enlisted the Hawaii telescope and others in Chile. Wesley was interiewed by Wired last July after the discovery, and he describes his equipment and viewing experiences. Wesley is more recently known for having discovered a giant white storm on Saturn.

The press release quotes Orton about the significance of the conclusion.

“Both the fact that the impact itself happened at all and the implication that it may well have been an asteroid rather than a comet shows us that the outer solar system is a complex, violent and dynamic place, and that many surprises may be out there waiting for us. There is still a lot to sort out in the outer solar system.”

 

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