A 10-km asteroid crashed into Earth near the site of the small town of Chicxulub in Mexico at the end of the Cretaceous period, about 66 million years ago. The impact unleashed an incredible amount of climate-changing gases into the atmosphere, triggering a chain of events that led to the extinction of non-avian dinosaurs and 75% of life on the planet. According to new research, this was likely worsened by the fact that the Chicxulub asteroid struck at an angle of about 60 degrees — one of the deadliest possible angles. In the case of the Chicxulub asteroid impact and the end-Cretaceous mass extinction 66 million years ago, there’s no mystery about the shooter. (Space did it.) But the trajectory is interesting for other reasons, and researchers have long been trying to trace the path back out of the crater off the Yucatán coast. Unsurprisingly, 66 million years have taken their toll on the crater, so researchers have offered several very different answers. Did the asteroid hit from the southeast at a very low angle? Did it come from the southwest at a moderate angle? Many studies that needed to model the impact have simply defaulted to a 90-degree strike and avoided the whole argument. The details actually matter, though, and precisely which rocks get vaporized—and which climate-changing gases they release—depends on that impact angle.A lot of new research on the crater has been published recently thanks to a major expedition that included drilling a rock core down through the crater’s peak ring. (Impacts this violent leave a raised ring in the center rather than a single peak.) Researchers from Imperial College London revealed that the asteroid hit Earth at an angle of 60 degrees. Hitting at this exact angle maximised the amount of climate-changing gases and particles into the upper atmosphere.The ensuing nuclear winter killed the dinosaurs and wiped out 75 per cent of all life on Earth. “For the dinosaurs, the worst-case scenario is exactly what happened,” said Professor Gareth Collins from Imperial’s department of Earth Science and Engineering, who led the study.“The asteroid strike unleased an incredible amount of climate-changing gases into the atmosphere, triggering a chain of events that led to the extinction of the dinosaurs. This was likely worsened by the fact that it struck at one of the deadliest possible angles.”“We know that this was among the worst-case scenarios for the lethality on impact, because it put more hazardous debris into the upper atmosphere and scattered it everywhere — the very thing that led to a nuclear winter,” he added.Such a strike likely unleashed billions of tons of sulfur and other gases into the atmosphere, blocking the sun and leading to a dramatic cooling of the Earth’s climate.Older studies had found that the asteroid hit at a shallower angle and came from the southeast, Collins said.“This was based on a different interpretation of the geophysical data, which our work overturns, and observations at the time that suggested that the ejecta from the crater was asymmetric, with more ejecta in North America (to the northwest) than elsewhere,” he explained via email, referring to the material that was forced out as a result of the impact.