P15/112 - Present and future observations of a meteor shower in the Martian atmosphere - submitted 01/02/2008 Presented by: Apostolos Christou (Armagh Observatory) Co-authors: Jeremie Vaubaillon (1), Paul Withers (2); 1 - Spitzer Science Center, CalTech/ IMCCE, Paris; 2 - Center for Space Physics, Boston Status: Accepted as talk. 17:20-17:30 Abstract: Mars, like the Earth, intersects cometary meteoroid streams, an as-yet-unquantified source of exogenous material, including organics, coming to the Martian atmosphere and surface. By simulating numerically the dynamical evolution of trails of meteoroids ejected from several Jupiter-family and Halley-type comets, we have obtained quantitative, testable predictions for Martian meteor activity. These will enable the planning and execution of in situ observations of meteor activity on planets other than the Earth. In this talk we will concentrate on the meteoroid stream of comet 79P/du-Toit-Hartley, a relatively poorly-known member of the Jupiter-Family type of comets. We show that meteoroids ejected from this comet during past perihelion passages do find their way to the Martian atmosphere at specific times during the 20th and 21st centuries and should have measurable effects on the planetary environment. On two of these occasions, in April 2003 and March 2005, we have examined archived ionospheric profile data obtained by the Mars Global Surveyor (MGS) Radio Science experiment. In the 2003 case we see a statistically significant feature that is consistent in time, location and altitude with our predictions while in 2005 no such signature was detected (Christou et al., A&A 471, 321–329, 2007). We discuss these observations, how they relate to our knowledge of the cometary properties and highlight the need for observational characterisation of the Mars-crossing comet population with Earth-based facilities. Finally, we issue predictions for exceptional 79P-related meteor activity that should be similarly observable by in-situ instrumentation during the next decade of Mars exploration.