We know that asteroids and comets exist, but where do they come from? In chapter 8, I learned that asteroids and comets are formed from the “leftovers” of planet formation. Asteroids are the rocky leftovers of small planets in the inner solar system, whereas comets are the icy leftovers of small planets in the outer solar system. Scientists have evidence of these conclusions from meteorite analysis, along with visits on spacecrafts. There was even a theory called the nebular theory which predicted that comets existed in the Kuiper belt long before anyone discovered the comets. The asteroids and comets that are left in our solar system are only a small percentage of the total number that has existed throughout the universe. The others have either gone into deep space due to gravity, while others have collided with planets and left behind impact craters. An example of an impact crater is that people speculate that the extinction of dinosaurs occurred because an asteroid struck Earth. The majority of these collisions happened in the first couple of hundred million years of the solar system’s existence, which is now called the period of heavy bombardment. These impacts probably altered the universe in necessary ways that made life on Earth possible. Water was likely brought to Earth from impacts of water-being planetesimals, probably from the outer portion of the asteroid belt. I think this topic is very interesting because I would love to know more about what knowledge researchers have about the changes that occurred in the solar system due to different collisions, that eventually made our life possible. This also makes me think that there are probably other forms of life out in space because with the different collisions, I doubt that only one place was formed to be habitable.