The impact of a large object with Jupiter in July 2009

TL;DR

This paper reports the observation of a rare large impact on Jupiter in July 2009, analyzing its properties, probable origin, and implications for impact frequency on the planet.

Contribution

It provides detailed analysis of the 2009 impact, compares it with the 1994 Shoemaker-Levy 9 event, and suggests impact rates may be higher than previously estimated.

Findings

Impactor was likely an icy body 0.5-1 km in size

Impact rate may be five to ten times higher than previously thought

Optimal detection filters are at 890-nm and K-band wavelengths

Abstract

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.