Atmospheric Disturbances and Radiation Impulses Caused by Large-Meteoroid Impacts on the Surface of Mars. I. Formation and Evolution of Dust Cloud

We consider the mechanisms of the formation of dust ejected from craters produced by large-meteoroid impacts on the Martian surface, as well as the mechanisms of the elevation of dust that already existed on the surface, due to impulsed aeolian processes. Detailed numerical calculations of the dust injection, the shock wave propagation, and the formation and evolution of the dust cloud are carried out for vertical impacts of meteoroids with sizes from 1 m to 100 m. The results of these calculations show that dust raised by a 1-m impactor is sufficient to produce a local dust storm, while the mass of dust formed in impacts of large bodies is comparable to the mass of a regional or even a global dust storm. The impact detection rates for 1-, 5-, 20-, and 100-m-sized meteoroids are estimated to be a few impact events per year, one event in every 5–6 years, one event in every 300–800 years, and one event in every 5000–20000 years, respectively. In the last case, the thickness of the global layer of precipitated dust and small fragments, which has been formed through impacts over a period of 10⁷–10⁸ years, is comparable to the thickness of the global dust layer on the Martian surface. In the first case, the mass of raised dust is greater than that for typical dust devils. The speed of impulsed wind at large distances from the impact site is shown to exceed the critical speed at which the blowing-off of dust from the surface begins. Some factors that may enhance the dust ejection have been previously ignored in numerical calculations. We discuss here the role of these factors. The second part of our study deals with the determination of the impact-induced radiation impulse and the estimation of its effect on the rise of dust.