Asteroid impact on Mars. Illustration of an asteroid impacting the surface of the planet Mars. This illustration is of a large impact, such as the one that occurred about 15 million years ago, sending debris flying into space. One piece of debris eventually impacted the Earth after millions of years in space, falling on Antarctica some 16,000 years ago. This rock, known as ALH 84001, was discovered in 1984. It contains microscopic structures that resemble the fossils of primitive life forms.