NEOWISE observations of comet C/2013 A1 (Siding Spring) as it approaches Mars

TL;DR

This study reports NEOWISE infrared observations of comet C/2013 A1 (Siding Spring) during its approach to Mars, analyzing its activity levels, Af {ho} values, and CO/CO2 production rates at different heliocentric distances.

Contribution

First infrared observations of comet C/2013 A1 (Siding Spring) during its approach to Mars, providing data on activity and gas production rates.

Findings

Activity increased from January to July 2014

Activity decreased by September 2014 before Mars approach

Measured Af {ho} values and CO/CO2 production rates

Abstract

The Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) mission observed comet C/2013 A1 (Siding Spring) three times at 3.4 {\mu}m and 4.6 {\mu}m as the comet approached Mars in 2014. The comet is an extremely interesting target since its close approach to Mars in late 2014 will be observed by various spacecraft in-situ. The observations were taken in 2014 Jan., Jul. and Sep. when the comet was at heliocentric distances of 3.82 AU, 1.88 AU, and 1.48 AU. The level of activity increased significantly between the Jan. and Jul. visits but then decreased by the time of the observations in Sep., approximately 4 weeks prior to its close approach to Mars. In this work we calculate Af\r{ho} values, and CO/CO2 production rates.