In fact , all the known V-type asteroids taken together account for only about 6 % of the ejected volume , with the rest presumably either in small fragments , ejected by approaching the 3:1 Kirkwood gap , or perturbed away by radiation pressure . In fact , all the known V-type asteroids taken together account for only about 6 % of the ejected volume , with the rest presumably either in small fragments , ejected by approaching the 3:1 Kirkwood gap , or perturbed away by the Yarkovsky effect or radiation pressure .