433 Eros is an S-type near-Earth asteroid approximately 34.4×11.2×11.2 kilometres (21.4×7.0×7.0 mi) in size, the second-largest near-Earth asteroid after 1036 Ganymed. It was discovered in 1898 and was the first near-Earth asteroid discovered. It was the first asteroid orbited by an Earth probe (in 2000). It belongs to the Amor group.
Eros is a Mars-crosser asteroid, the first known to come within the orbit of Mars. Objects in such an orbit can remain there for only a few hundred million years before the orbit is perturbed by gravitational interactions. Dynamical integrations suggest that Eros may evolve into an Earth-crosser within as short an interval as two million years, and has a roughly 50% chance of doing so over a time scale of 108–109years. It is a potential Earth impactor, comparable in size to the impactor that created Chicxulub crater and led to the extinction of the dinosaurs.
The NEAR Shoemaker probe visited Eros twice, first with a 1998 flyby, and then by orbiting it in 2000 when it extensively photographed its surface. On February 12, 2001, at the end of its mission, it landed on the asteroid’s surface using its maneuvering jets.
Eros was discovered on August 13, 1898 by Gustav Witt in Berlin and Auguste Charloisat Nice. Witt was taking a 2-hour exposure of Beta Aquarii to secure astrometric positions of asteroid 185 Eunike.