Named in honor of Ernst J. Opik {1893–1985} on the occasion of his 85th birthday. Over a career spanning more than 60 years he has influenced almost every branch of astronomy. In particular he has developed the discipline of statistical celestial mechanics and of methods for estimating the lifetimes of small bodies on planet-crossing orbits. In 1951 he computed the probability of collision with Mars of the Mars-crossing minor planets recognized at that time, and 14 years before their discovery by the Mariner 4 spacecraft he inferred that it would be worthwhile to search for impact craters on Mars. It is therefore fitting that (2099) Opik should be a Mars-crosser. (M 4548) _ _.