SwRI's evolutionary models of the main Asteroid Belt were modeled by a team. They discovered that impactors like the one that ended reign of the dinosaurs most likely come from the outer half. It was also found that the region is 10 times more likely to receive delivery than previously thought. Credit: SwRI/Don DavisAccording to the impactor that killed the dinosaurs, the impactor was likely to have come from the outer half the main asteroid Belt. This region had been thought to be home to few impactors. Southwest Research Institute researchers have found that large asteroids are delivered to Earth from this region at least 10 times more often than previously thought. Additionally, the composition of these bodies matches what we know about the impactor that killed the dinosaurs.Dr. David Nesvorn and Dr. William Bottke, along with Dr. Simone Marchi, combined computer models of asteroid development with observations of known asteroids in order to examine the frequency of Chicxulub events. Chicxulub Crater, which measures over 90 miles in diameter, was formed by a body measuring 6 miles across that struck Mexico's Yucatan peninsula, some 66 million years ago. The mass extinction that brought down the dinosaurs was caused by this massive explosion. Although much has been known about Chicxulub over the past several decades, every advancement has brought new questions."Two crucial questions remain unanswered: "What was the source for the impactor?" "Bottke said that two critical questions remain unanswered: "What was the source of the impactor?" and "How often have such impact events occurred on Earth in recent history? Bottke stated.Geologists previously examined rock samples 66 million years old found on the ground and in drill cores to investigate the Chicxulub Impact. The impactor looked similar to the carbonaceous-chondrite meteorite class, which are some of the most beautiful materials in the solar system. Curiously, although carbonaceouschondrites are found on many bodies measuring miles across that approach the Earth's surface, they are not common at the size required to cause the Chicxulub Impact with any reasonable probability."We decided that we would look for the Chicxulub siblings," Nesvorn, the lead author of the paper detailing the research, said.Bottke, who was one of the co-authors, said that "to explain their absence, many past groups have simulated large comet and asteroid breakups within the inner solar system. Looking at surges of impacts upon Earth with the largest one producing Chicxulub, crater." While many models were interesting, none of them was able to match what we know about comets and asteroids. It felt like we were missing something.The team developed computer models to track the escape routes of objects from the main asteroid Belt, which is a region of small bodies between Jupiter and Mars. These objects can drift into dynamical escape hatches where they are subject to the gravitational pushes of the planets. This allows them to orbit Earth in close proximity. NASA's Pleaides Supercomputer was used to track 130,000 model asteroids over hundreds of millions of year. The outer half of the Asteroid Belt, which is the furthest from Sun, was particularly important. Surprised, they discovered that asteroids measuring 6 miles in diameter struck the Earth 10 times more frequently than previously estimated.Marchi, co-author, said that the result was intriguing because it shows that the outer half the asteroid belt contains large numbers of carbonaceous and chondrite impactors. However, the simulations by the team can reproduce, for the very first time, the orbits of large asteroids at the edge of approaching Earth. "Our explanation of the Chicxulub-impactor's origin fits perfectly with the existing knowledge about how asteroids evolve."The team discovered that asteroids measuring 6 miles in diameter hit Earth approximately once every 250 million year on average. This gives rise to reasonable chances that the Chicxulub impactor occurred around 66 million years ago. The team also found that nearly half of the impacts were carbonaceous chondrites. This is a good match for what we know about the Chicxulub Impactor.Nesvorn stated that this work would help to better understand the Chicxulub impact and also reveal where other large impactors of Earth's deep history might have come from.Icarus has published a paper on this topic titled "Dark Primitive Asteroids account for a large share of K/Pg Scale Impacts to the Earth."Study further Comet at the edge of the solar system that killed dinosaurs: exploreAdditional information: David Nesvorn and colleagues, Dark primitive asteroids account to a large portion of K/Pg impact on the Earth, Icarus (2021). Information from the Journal: Icarus David Nesvorn and colleagues, Dark primitive asteroids account to a large portion of K/Pg -scale impacts on Earth, (2021). DOI: 10.1016/j.icarus.2021.114621
