Antarctic meteorites that hail from Mars
Who would think that a rock found in remote, freezing Antarctica, could be useful for studying Mars? In fact, teams of geologists congregate in Antarctica to find meteorites. Some of the meteorites originated on Mars. Although meteorites fall all over the Earth, the cold, dry conditions of the South Pole are ideal for preserving them. The movements of ice sheets concentrate the meteorites against mountainsides. The intense, Antarctic winds erode the ice surface away. That leaves meteorites exposed.
Getting to Antarctica, however, is not a short journey for a meteorite. Each meteorite was originally part of some larger solar system object. It could have been a planet, moon or asteroid. The solar system is an active place, with lots of objects in motion. The area between the orbits of Mars and Jupiter, called the asteroid belt, is like a bumper car pavilion when viewed over long periods of time. Objects are continually colliding. That causes pieces to get knocked off and thrown into irregular orbits.
Every once in a while, an object gets bumped onto a trajectory that brings it to Earth. If it reaches Earth's surface, it officially becomes a meteorite. But, objects may stay in the asteroid belt for millions of years before getting bumped out. For example, meteorites called nakhlites were ejected from Mars about 11 million years ago. It happened because of a collision. They landed on Earth 10,000 years ago or less. This means that they were kicking around in space for at least 10,990,000 years.
What that also means is that meteorites are made of very old materials. Nakhlites are made of 1-billion-year-old magma. It provides clues about geologic activity on a younger Mars. Some meteorites can be traced back even further. They go back to a dynamic period about 3.9 billion years ago. It was called the Late Heavy Bombardment. The Earth, its Moon (look at all the craters!) and other planets were bombarded with meteorites for reasons that scientists are still trying to understand.
Learn more about collisions in space and meteorites from Mars in a live "Smithsonian Science How" webcast. It airs on Thursday, June 9, 2016. In Exploring the Solar System with Antarctic Meteorites (at 11 a.m. and 2 p.m. EDT on the Q?rius website), meteoriticist Dr. Cari Corrigan will show you some meteorites that are kept in collections at the National Museum of Natural History, while answering your questions live. Get teaching resources to use with the webcast.
CRITICAL THINKING QUESTION
Why are cold, dry conditions best for preservation?
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