The orbit of the planet Mars is host to the remains of an ancient collision that created many of its Trojan asteroids, a new study has concluded. It paints a new picture of how these objects came to be and may even hold important lessons for deflecting asteroids on a collision course with our own planet. The findings were presented at the annual Meeting of the Division for Planetary Sciences of the American Astronomical Society in Denver last week, by Dr. Apostolos Christou, a Research Astronomer at the Armagh Observatory in Northern Ireland, United Kingdom.
Trojan asteroids, or “Trojans,” move in orbits with the same average distance from the Sun as a planet. This may seem as a precarious state to be in, as eventually the asteroid either hits the planets or is flung, by the planet’s gravity, on an entirely different orbit.
But solar and planetary gravity combine in such a way as to create dynamical “safe havens” 60 degrees in front and behind the planet’s orbital phase. The special significance of these, as well as three other similar locations in the so-called three-body problem, was worked out by
18th century French Mathematician Joseph-Louis Lagrange. In his honor, they are nowadays referred to as the Lagrange points. The point leading the planet is referred to as L4; that trailing the planet as L5.