The Cape York Meteorites, the Younger Dryas, and Their Possible Association with the Hiawatha and Paterson Impact Craters

Abstract

The recent discovery of the Hiawatha and Paterson impact craters in north-western Greenland has motivated three intriguing questions: are they associated with the Cape York meteorites, did they form at the same time, and can one or both of the craters be associated with the abrupt cooling of the Earth, some 10 -13,000 years ago, at the onset of the Younger Dryas. To address the first question, we review the properties of the Cape York meteorites and their associated strewn field. Using the Earth Impact Effects simulator, it is found that the strewn field is generally consistent with the entry of a 2 to 6-m diameter iron asteroid into the Earth's atmosphere some 1 to 2 million years ago. The latter, terrestrial residency age of the meteorites, however, remains preliminary, and further radionuclide analysis is required to confirm the fall epoch. The possibility that the Cape York meteorites are progenitor fragments ejected at the time of crater formation has been investigated with an atmospheric flight program, and while it is possible to account for progenitor fragments traveling the 300-km distance between either crater location and the strewn field, this scenario is deemed unlikely. Indeed, the craters each being in excess of 30-km in diameter would indicate the complete vaporization of the impactors. It is concluded that the Cape York meteorites are unlikely to be related to the formation of either of the craters. Additionally, the 183-km separation between such large craters is remarkable and suggestive of a contemporaneous origin. We investigate this latter possibility, and while it cannot be fully ruled out at the present time, it is, on the basis of Near-Earth Object population statistics, deemed to be highly unlikely that they formed at the same time. This issue, however, will only be fully resolved once improved age estimates become available. Indeed, better crater formation ages will also shed more light upon their possible association with the Younger Dryas onset. With respect to the global climate excursion associated with the Younger Dryas, we review the possibility that the crater progenitor bodies were derived from the Taurid Complex, finding that this scenario is deserving of further study. Moving forwards, however, the conservative hypothesis, that the two craters are temporally distinct, not related to the Cape York meteorites and/or contemporaneous with the Younger Dryas onset, is favored.