Grant: Discovery Grants Program - Individual

The small bodies in the solar system (asteroids, comets, centaurs and trans-Neptunian objects) are relics from the formation stage of our solar system. In many cases they contain primitive material which has not experienced substantial processing. Their physical structure, chemistry and dynamical evolution offer a unique window into the early solar system informing formation models of our solar system and other planetary systems. Fragments of these bodies occasionally impact the Earths atmosphere, producing ionization, radiation and shocks in the form of meteors. By studying how the fragment (meteoroid) ablates in the atmosphere we can reconstruct its properties (bulk density, strength, grain sizes) and by extension learn about its parent body. The approach of this proposal is to observe meteoroids ranging in size from dust grains to boulders interacting with the atmosphere by recording their light, ionization and shock production. By measuring their mass and numbers at all sizes I will accurately estimate the flux of these bodies to Earth. For smaller meteoroids this will help in refining the amount of meteoritic material accumulated by the Earth. For larger objects (meter-decameter-scale) I will measure their impact effects, particularly shock strength, as this is critical to constraining how fireballs can cause damage at the ground. In the wake of the Feb 15, 2015 Chelyabinsk airburst over Russia there is a pressing need for better ground damage models to help inform civil defence officials in the event another multi-meter sized near-Earth object is detected just prior to impact. For these larger events, recovery of meteorites also provides ground-truth for precursor body composition and structure. Such larger impactors also form the ultimate calibration for entry models, if we are able to simultaneously document the fireball in the atmosphere. Through modelling of the breakup behavior in the atmosphere at all sizes I will measure the strength and bulk density of a large number of meteoroids and correlate this with their pre-impact orbits. The result will be a detailed coordinated picture of the strength/structure and orbital origins for dust-to-boulder sized objects colliding with the Earth. Ultimately this will build up a picture of the origins and present ecology of small bodies in near-Earth space both in terms of dust and larger Near-Earth Objects (NEOs). The resulting road-map of the number and physical characteristics of dust to boulder sized meteoroids near Earth is of practical importance for planetary defence and for the protection of spacecraft from meteoroid impacts. This information is also needed for upcoming spacecraft missions such as the NASA Asteroid Redirect Mission, which seeks to return a boulder-sized rock to lunar orbit from a near-Earth asteroid.