Asteroids: their physical properties and why they matter

Kurzfassung

Most asteroids and comets are thought to be remnant collisional fragments of planetesimals, the building blocks from which planets in our solar system formed around 4.5 billion years ago. Asteroids and comets from diverse regions of the planetary disk probably enriched the early Earth and other planets in minerals, water, and organic materials. In later epochs, impacts of asteroids and comets on the Earth may have abruptly altered the course of evolution and paved the way for mankind. However, mankind should now be aware that this natural process has not ceased. In particular, the current population of so-called near-Earth asteroids contains many objects that are considered potentially hazardous. On the positive side, near-Earth asteroids may prove to be valuable sources of raw materials (metals, water, rocket propellant, etc.) for future generations. I will illustrate the significance of asteroids for life on Earth and describe recent results of astronomical research into relevant physical properties of these bodies. This research may help us to better understand how harmless asteroids become hazardous and how we can prevent a catastrophic impact on our planet.