Yesterday, 14 November 2018, the discovery of a possible large new impact crater on Earth was publicly announced. The crater, on the northwest coast of Greenland, was revealed by the seasonal retreat of the ice sheet, partially uncovering a circular feature roughly 20 miles in diameter, presently still filled with ice.
The debris from the crater rim exhibits unusually strong traces of platinum, palladium and rhodium, as well as traces of what appear to be grains of terrestrial quartz that has undergone severe mechanical shock, a diagnostic feature of violent impact events that generate high shock pressures. The article is featured on today’s (15 November) Space.com, along with text that whets the appetite while flirting with the boundaries of the truth. We are assured in that article that the shocked quartz grains are the result of the “impact’s force abruptly melting rock”, whereas in reality melting is guaranteed to erase evidence of severe mechanical shock. We are also unconvinced by the article’s attribution of the impact to a “giant iron meteorite” through the identification of the platinum-group metals in the debris near the crater. In fact, the large majority of all asteroids and meteorites of asteroidal origin are rich in these elements whether or not they are made of metal, simply because these elements are ubiquitous in chondritic (primitive) meteorites; indeed, they are also present, albeit in somewhat diluted form, in comets.
The simplest interpretation of the available data, at this early point in the crater’s exploration, is that it was caused by the impact of a near-Earth asteroid or comet with a diameter of about 2.5 to 3 kilometers. About 1000 Earth-crossing asteroids larger than 1 kilometer in diameter are presently known—and carefully tracked.
Alternative histories? The circular shape may be a misleading consequence of some impact-free mode of origin (such as an explosive volcanic eruption), and the platinum-group metals may also be a consequence of a deep-seated volcanic event. Careful analysis of the proportions of all the platinum-group metals (“PGMs”) and verification of the shocked silica grains should verify or discredit the story of an impact origin of the crater.
Let’s keep an eye on the news about this event. The fact that this news appears on the very day that my science fiction book “A Rending Clash of Worlds: I. The Astronomers”, a story about the discovery of an Earth-threatening asteroid in 1871, appears as a free offering on Amazon.com is purely coincidental (or reflects a truly high-level conspiracy)!