Cometary Impacts on the Biosphere

The contribution of sulphur dioxide from ablating micrometeorites to the atmospheres of Earth and Mars

“…Examination of the near-Earth asteroid size-frequency distribution and frequency intervals (Stokes et al, 2003) suggests that the average annual mass delivered by micrometeorites and small meteoroids is approximately 25% of the average total infall rate. A similar estimate of the mass balance between micrometeorites and large bodies was given by Steel (1997), at around 20-30%, although Maurette et al (2000) noted that the increased measurement of the micrometeorite flux of Love and Brownlee (1993) enables this 20-30% to be increased to around 40-60%. Hence, like Maurette (1998), we will assume that the situation during the LHB was similar to that of the present day, and assume that 33% of the infalling mass during the LHB was in the form of small meteorites or micrometeorites that ablated in the atmosphere.…”

COSAC Onboard Rosetta: A Bioastronomy Experiment for the Short-Period Comet 67P/Churyumov-Gerasimenko

“…Delivery of cometary material to Earth occurs as a result of the "gentle and continuous rainfall" of micronand submicron-size grains the Earth encounters as it orbits the Sun (Sykes et al, 2004). In contrast to this essentially non-destructive process, however, much more violent deliveries of cometary material have occurred, and will continue to occur, by way of high-speed collisions with cometary nuclei on Earth (Steel, 1996;Thomas and Brookshaw, 1996).…”