This area will cover relevant news of the threat to the planet from Near Earth Objects (NEOs) including concepts and designs for mitigation. All opinions are those of the author.

18 May 2010

Paper on 2009 Jupiter Impact Event

A new paper on the 2009 Jupiter Impact Event.

The impact of a large object with Jupiter in July 2009

Authors: A. Sánchez-Lavega, A. Wesley, G. Orton, R. Hueso, S. Perez-Hoyos, L. N. Fletcher, P. Yanamandra-Fisher, J. Legarreta, I. de Pater, H. Hammel, A. Simon-Miller, J. M. Gomez-Forrellad, J. L. Ortiz, E. García-Melendo, R. C. Puetter, P. Chodas
(Submitted on 13 May 2010)


On 2009 July 19, we observed a single, large impact on Jupiter at a planetocentric latitude of 55^{\circ}S. This and the Shoemaker-Levy 9 (SL9) impacts on Jupiter in 1994 are the only planetary-scale impacts ever observed. The 2009 impact had an entry trajectory opposite and with a lower incidence angle than that of SL9. Comparison of the initial aerosol cloud debris properties, spanning 4,800 km east-west and 2,500 km north-south, with those produced by the SL9 fragments, and dynamical calculations of pre-impact orbit, indicate that the impactor was most probably an icy body with a size of 0.5-1 km. The collision rate of events of this magnitude may be five to ten times more frequent than previously thought. The search for unpredicted impacts, such as the current one, could be best performed in 890-nm and K (2.03-2.36 {\mu}m) filters in strong gaseous absorption, where the high-altitude aerosols are more reflective than Jupiter's primary cloud.

Comments: 15 pages, 5 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Journal reference: The Astrophysical Journal Letters, 715, 2, L150 (2010)
DOI: 10.1088/2041-8205/715/2/L155
Cite as: arXiv:1005.2312v1 [astro-ph.EP]

Link: Paper Reference

Link: Paper (PDF)

Selections from the MIT Technology Review article...

Estimating the likelihood of such impacts is hard for a gas giant like Jupiter because the events leave no long-lasting scars on the surface. Jupiter's bruise has already faded away.

So astronomers have to rely on historical records. Before last year's impact, astronomers knew only of the Shoemaker-Levy impact and a possible impact observed by the Italian astronomer Giovanni Cassini in 1640. Together with other evidence such as crater counts on Jupiter's large moons and various theoretical calculations, astronomers guessed that Jupiter was liable to a strike perhaps as rarely as once in every 350 years.

Sánchez-Lavega and co say that last year's strike significantly changes these numbers. Seeing two strikes in 15 years means that that Jupiter may be liable to be hit as often as once a decade. The reason we haven't seen impacts before is simple: digital cameras and image processing techniques have only become easily available to amateurs in the last ten years. (Before that, even professionals often had to rely on hand drawn pictures of the planets.)

Link: MIT Technology Review Article

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