Contemporary Atmospheric Escape at Mars: Implications for Astrobiology

The development of life on Earth is believed to have resulted in permanent changes in the composition of the atmosphere. A search for atmospheric biosignatures is one of the major objectives of the powerful telescopes currently being designed to search for terrestrial extrasolar planets. In our own solar system, Mars is considered one of the best candidates for the development of life. However, identification of an atmospheric biosignature on Mars is not possible until all potential abiotic processes have been accounted for. At present we are particularly limited by our understanding of the role of atmospheric escape at Mars through its history. This paper summarizes the present understanding of the physics of atmospheric escape to space at Mars, discusses the constraints on the estimates of loss (both at present and over Martian history), suggests important measurements and model improvements that would significantly improve our understanding of this important process, and relates the current understanding to the possibility of detection of an atmospheric biosignature.