Physical Properties of Basalt Ejecta Boulders at Lonar Crater, India: Insights Into the Target Heterogeneity and Impact Spallation Processes in Basalt With Application to Mars

When a hypervelocity meteorite strikes the planetary surface, it produces a layer of large spall fragments (boulders) from the target's surface and become parts of the impact crater ejecta. The measurements of physical and geometric properties of these ejecta boulders are useful for quantifying the conditions of impact cratering. Hence, we measured these quantities using the basalt boulders at Lonar crater in India and quantified the gross physical properties of the preimpact target. These values were used in the impact cratering equations and theoretical spallation models to determine the size and velocity of the impactor that would produce the spall sizes similar to the observed boulder sizes at Lonar. Many fresh impact craters on Mars are also formed on targets comparable to Lonar crater. Hence, we used the Lonar target properties in the spallation model of a Martian impact crater of similar size to Lonar. The results suggest that a lower‐velocity impact into a Lonar‐like target would produce spall fragments similar to the observed boulder sizes around the Martian crater. In addition, the ejecta boulders of Lonar and the Martian impact craters provide clues to the extent of aqueous alteration in the target rocks.

Figure: Lonar crater and crater in Mars




Lakshmi, K. J. P., & Kumar, P. S. (2020). Journal of Geophysical Research: Planets, 125,e2020JE006593.