Can life travel between planets?
There are several ways in which living organisms can travel millions of kilometres through space and spread between planets. The most common way in which this happens is through meteorites. Meteorites are rocks from space which crash on a planet’s surface. Most of the meteorites which crash on Earth are small asteroids. However, several of these meteorites are believed to be rocks which were once on the surface of Mars, our neighbouring planet. How is this possible? When a big asteroid collided with Mars (like the one which killed the dinosaurs) sometime in the past, a large number of rocks from the surface of Mars would have been thrown into space. Many of these rocks fall back down to Mars due to the planet’s gravity. However, some of these rocks will be travelling fast enough to escape Mars and start orbiting the Sun. The orbits of some of these rocks would be elliptical and cross the Earth’s orbit. When the rocks get close enough to Earth, they are pulled by Earth’s gravity and cra...