First results on Martian carbon monoxide from Herschel/HIFI observations

TL;DR

This study presents initial Herschel/HIFI observations of Martian CO, revealing temperature profiles consistent with models up to 45 km and a CO mixing ratio around 980 ppm, confirming previous measurements.

Contribution

First analysis of Herschel/HIFI CO data on Mars, providing temperature and CO mixing ratio profiles with initial validation against models and prior observations.

Findings

Temperature profile matches GCM predictions up to 45 km

CO mixing ratio is approximately 980 ppm

Results agree with previous Herschel/SPIRE measurements

Abstract

We report on the initial analysis of Herschel/HIFI carbon monoxide (CO) observations of the Martian atmosphere performed between 11 and 16 April 2010. We selected the (7-6) rotational transitions of the isotopes ^{13}CO at 771 GHz and C^{18}O at 768 GHz in order to retrieve the mean vertical profile of temperature and the mean volume mixing ratio of carbon monoxide. The derived temperature profile agrees within less than 5 K with general circulation model (GCM) predictions up to an altitude of 45 km, however, show about 12-15 K lower values at 60 km. The CO mixing ratio was determined as 980 \pm 150 ppm, in agreement with the 900 ppm derived from Herschel/SPIRE observations in November 2009.