A recent study by planetary scientists has shed new light on why meteorites, specifically carbonaceous chondrites, have less water than asteroid pieces. The research suggests that a significant amount of the removal of weak, hydrated material occurs beforehand in space.
Carbonaceous chondrites are rich in water and organic compounds, making them an essential window into the solar system’s infancy. However, most asteroids are believed to be water-rich as well, with models predicting that over half of meteorites should also have carbonaceous compositions. Yet, only about 4% of meteorites found on Earth are actually carbonaceous.
The study used data from NASA’s OSIRIS-REx and JAXA’s Hayabusa2 missions, which retrieved pristine samples from asteroids Bennu and Ryugu, respectively. By analyzing these samples, scientists were able to examine the asteroid’s composition in detail.
Researchers found that many asteroid pieces don’t make it to Earth due to heat stress caused by their orbit taking them close to the Sun. The carbonaceous material tends to be weak and hydrated, which makes it more susceptible to breaking down through heat stress. This process effectively removes weak, hydrated boulders from the population of objects near Earth.
Only 30-50% of the remaining objects survive the atmospheric passage and become meteorites. In contrast, debris pieces whose orbits bring them closer to the Sun tend to be significantly more durable, making them more likely to survive the difficult passage through Earth’s atmosphere.
This study indicates that much of the removal of carbonaceous material occurs beforehand in space, contradicting previous assumptions that Earth’s atmosphere alone explains the scarcity of these meteorites. The findings provide valuable insights into the solar system’s infancy and have implications for future research on meteoroid compositions.
Source: https://www.yahoo.com/news/why-meteorites-hit-earth-less-143242328.html