Chicxulub crater
The Chicxulub crater (IPA: [t͡ʃikʃuˈluɓ] cheek-shoo-LOOB) is an impact crater buried underneath the Yucatán Peninsula in Mexico. Its center is offshore, but the crater is named after the onshore community of Chicxulub Pueblo (not the larger coastal town of Chicxulub Puerto).[3] It was formed slightly over 66 million years ago when an asteroid, about ten kilometers (six miles) in diameter, struck Earth. The crater is estimated to be 200 kilometers (120 miles) in diameter and 20 kilometers (12 miles) in depth. It is believed to be the second largest impact structure on Earth, and the only one whose peak ring is intact and directly accessible for scientific research.[4]
"Chicxulub" redirects here. For other uses, see Chicxulub (disambiguation).Chicxulub crater
Confirmed
200 km (120 mi)
20 km (12 mi)
10 km (6.2 mi)
66.043 ± 0.043 Ma
Cretaceous–Paleogene boundary[2]
No
Yes
CM or CR type carbonaceous chondrite
Mexico
The crater was discovered by Antonio Camargo and Glen Penfield, geophysicists who had been looking for petroleum in the Yucatán Peninsula during the late 1970s. Penfield was initially unable to obtain evidence that the geological feature was a crater and gave up his search. Later, through contact with Alan R. Hildebrand in 1990, Penfield obtained samples that suggested it was an impact feature. Evidence for the crater's impact origin includes shocked quartz, a gravity anomaly, and tektites in surrounding areas.[3]
The date of the impact coincides with the Cretaceous–Paleogene boundary (commonly known as the K–Pg or K–T boundary). It is now widely accepted that the devastation and climate disruption resulting from the impact was the primary cause of the Cretaceous–Paleogene extinction event, a mass extinction of 75% of plant and animal species on Earth, including all non-avian dinosaurs.[4]
Astronomical origin of impactor[edit]
The original 1980 paper describing the crater suggested that it was created by an asteroid around 6.6 kilometers (4.1 mi) in diameter.
A 2007 Nature report proposed an origin for the Chicxulub asteroid.[44] The authors, William F. Bottke, David Vokrouhlický, and David Nesvorný, argued that a collision in the asteroid belt 160 million years ago between a 170 km (110 mi) diameter parent body and another 60 km (37 mi) diameter body resulted in the Baptistina family of asteroids, the largest surviving member of which is 298 Baptistina. They proposed that the Chicxulub asteroid was also a member of this group.[68] Subsequent evidence has cast doubt on this theory. A 2009 spectrographic analysis revealed that 298 Baptistina has a different composition more typical of an S-type asteroid than the presumed carbonaceous chondrite composition of the Chicxulub impactor.[69] In 2011, data from the Wide-field Infrared Survey Explorer revised the date of the collision which created the Baptistina family to about 80 million years ago, allowing only 15 million years for the process of resonance and collision, which takes many tens of millions of years.[70] In 2010, another hypothesis implicated the newly discovered asteroid 354P/LINEAR, a member of the Flora family, as a possible remnant cohort of the K–Pg impactor.[71] In 2021, a numerical simulation study argued that the impactor likely originated in the outer main part of the asteroid belt.[72] In 2021, four independent laboratories reported elevated concentrations of iridium in the crater's peak ring, further corroborating the asteroid impact hypothesis.[73] T
Some scholars have argued that the impactor was a comet, not an asteroid. Two papers in 1984 proposed it to be a comet originating from the Oort cloud, and it was proposed in 1992 that tidal disruption of comets could potentially increase impact rates.[28] In 2021, Avi Loeb and a colleague suggested in Scientific Reports that the impactor was a fragment from a disrupted comet.[74] A rebuttal in Astronomy & Geophysics countered that Loeb et al. had ignored that the amount of iridium deposited around the globe, 2.0×108–2.8×108 kg (4.4×108–6.2×108 lb), was too large for a comet of the size implied by the crater, and that they had overestimated likely comet impact rates. They concluded that all available evidence strongly favors an asteroid impactor, effectively ruling out a comet.[28]