An international research team recently published a paper in the American journal Science, saying that through the analysis of the sediment in Mexico's Hiksurub region, they believed that the object that hit the Earth about 66 million years ago and caused the extinction of non avian dinosaurs was a carbon asteroid from the outer solar system. Previous studies generally believed that the impact on the Xiksurub region and the corresponding changes in the Earth's environment led to a mass extinction, including the extinction of non avian dinosaurs. But there are still many unanswered questions about the properties of the impactor. Researchers from the University of Cologne and other institutions in Germany took rock samples at three points of Hiksurub crater. The test results show that the sample is rich in metal elements such as iridium, ruthenium, and platinum. These metal elements are rare on Earth, but very common on asteroids. During the analysis of ruthenium isotope ratios, researchers discovered clues about the source of the impactor. Ruthenium has 7 stable isotopes with different mixing characteristics in celestial bodies from different sources. By comparing the sample data with rock samples from other eight impact sites in the past 3.5 billion years, the research team found that the ruthenium isotope characteristics left by the Hiksurub impact site did not match with the siliceous asteroids from the inner solar system, but very matched with the carbon asteroids from the outer solar system. It was once believed that the impactor was a part of a comet that disintegrated under the gravitational force of the sun. But the team conducting this study believes that the ruthenium isotope data of comet fragments do not match the characteristics of the impact point. (New Society)