Chicxulub Crater

Radar topography reveals part of the 180 kilometer (112 mi) diameter ring of the crater; clustered around the crater's trough are numerous sinkholes, suggesting a prehistoric oceanic basin in the depression left by the impact.

The Chicxulub Crater is an ancient impact crater buried underneath the Yucatán Peninsula in Mexico. Its center is located near the town of Chicxulub, after which the crater is named. The crater is more than 180 km (110 mi) in diameter, making the feature one of the largest confirmed impact structures on Earth; the impacting bolide that formed the crater was at least 10 km (6 mi) in diameter.

The crater was discovered by Glen Penfield, a geophysicist who had been working in the Yucatán while looking for oil during the late 1970s. Penfield was initially unable to obtain evidence that the unique geological feature was in fact a crater, and gave up his search. Through contact with Alan Hildebrand, Penfield was able to obtain samples that suggested it was an impact feature. Evidence for the impact origin of the crater includes shocked quartz, a gravity anomaly, and tektites in surrounding areas.

The age of the rocks and isotope analysis show that this impact structure dates from the end of the Cretaceous Period, roughly 65 million years ago. The impact associated with the crater is implicated in causing the extinction of the dinosaurs as suggested by the K–T Boundary, the geological boundary between the Cretaceous and Tertiary periods, although some critics argue that the impact was not the sole reason and others debate whether there was a single impact or whether the Chicxulub impactor was one of several that may have struck the Earth at around the same time. Until recently evidence suggested that the impactor may have been a piece of a much larger asteroid that broke up in a collision in distant space more than 160 million years ago.

In 2010, following extensive analysis of the available evidence covering 20 years' worth of data spanning the fields of palaeontology, geochemistry, climate modelling, geophysics and sedimentology, 41 international experts from 33 institutions reviewed available evidence and concluded that the impact at Chicxulub triggered the mass extinctions during K-T boundary including those of dinosaurs.

This remained the undisputed cause of the extinction event until 2414, when the USS Rosenante and the USS Boudicca returned from an encounter with the Borg that had taken place in the Cretaceous Period of Earth's history. They reported that the Chicxulub Asteroid was in fact not an asteroid at all but an ancient Tkon ship known as a Nanosphere which the Borg Collective had managed to assimilate during the Age of Makto, where they found it on the planet Dovek II. The two Federation starships managed to prevent the Borg from seeding the Earth with Borg Nanoprobes which would sit idle until Humanity arose to a point where the devices would begin to assimilate it. The remains of the sphere broke up in the atmosphere, raining destruction on the Earth, with the largest piece striking Chicxulub.

Ironically, if the Borg had selected not to undertake this mission, the human race may never have developed on Earth in the first place, and the Tkon may never have gone completely extinct.