Collisions are at the core of solar system formation (Birth of Worlds), and continue to be one of the most important processes throughout our solar system.
Those impact scars, and the materials that make up the objects themselves, tell the story of our solar system's formation -- and how planets and their moons continued to change since those early days. This topic will explore the evidence of impacts and the stories told.
Today, Earth encounters many bits of ice and rock, and most burn up in the atmosphere. Some chunks make it to Earth's surface as meteorites. Impacts by larger objects, capable of damage to people or cities, are extremely rare. Currently, no known asteroids are predicted to collide with our world.
In the past, larger collisions occurred, with profound effects. Did you know that the Earth-Moon system most likely formed by the impact of the early Earth with another planet half Earth's size? The huge northern lowlands of Mars, with its very thin crust, are also likely the result of impacts -- and possibly one incredibly large impact! Impacts resurfaced planets and moons, put water on the Moon and Mercury, delivered materials needed by life to Earth and elsewhere, and caused at least one mass extinction -- and consequently the rise of mammals -- on Earth.
NASA scientists have created their own impacts to study this important process -- on the Moon during the LCROSS mission and on comet Tempel 1 during the Deep Impact mission.
Resources in this topic will let you explore impacts and the results of impacts, safely. And what about those objects that crash into large planetary bodies -- comets and asteroids? You can learn more about them in the Small Bodies / Big Impacts and Asteroids YSS topics.