What is a near-Earth asteroid?

We often hear from astronomers and other scientists about 'near-earth asteroids' - lumps of rock and metal that orbit through our Solar System, and pass close enough to our planet to pose an impact risk.

But many people wonder what this means, and ask additional questions. How many are there? Where do they come from? And why should we care about them?

In less than 90 seconds, our video will answer these questions and more, and show what ESA is doing about the risks they pose, helping to safeguard our planet.