The late Eocene Chesapeake Bay impact structure is a well-preserved example of one of Earth's largest impact craters, and its continental-shelf setting and relatively shallow burial make it an excellent target for study. Since the discovery of the structure over a decade ago [Edwards et al., 2004; Poag et al., 2004], test drilling by U.S. federal and state agencies has been limited to the structure's annular trough (Figure 1). In May 2004, the U.S. Geological Survey (USGS) drilled the first scientific test hole into the central crater of the Chesapeake Bay impact structure in Cape Charies,Virginia (Figure 1). This partially cored test hole, the deepest to date, penetrated postimpact sediments and impact breccias to a total depth of 823 m.