The Boulder Population of Asteroid 4 Vesta: Size?Frequency Distribution and Survival Time

Dawn's framing camera observed boulders on the surface of Vesta when spacecraft was in its lowest orbit (LAMO). We identified, measured, and mapped LAMO images, which have a scale 20 m per pixel. estimate that our sample is virtually complete down to boulder size 4 pixels (80 m). The largest 400 m-sized block Marcia crater floor. Relatively few reside large area relatively low albedo, surmised be carbon-rich ejecta Veneneia basin, either because form less easily here or live shorter. By comparing density around craters with known age, we find maximum lifetime about 300 Ma. size-frequency distribution (SFD) generally assumed follow power law. fit laws SFD by means likelihood method, but they do not well. Our analysis law exponents for other small Solar System bodies suggests derived exponent primarily function range. Weibull mimics this behavior fits often encountered rock grinding experiments, may result from fractal nature cracks propagating interior. propose that, general, particles (including boulders) follows rather than