Minor-planet moon Herculina does not have a significant satellite. There were other similar reports of asteroids having companions (usually referred to as satellites) in the following years. Also, a letter in "Sky & Telescope" magazine at this time pointed to apparently simultaneous impact craters on Earth (for example, the Clearwater Lakes in Quebec), suggesting that these craters were caused by pairs of gravitationally-bound objects. In 1993, the first asteroid moon was confirmed when the Galileo probe discovered the small Dactyl orbiting 243 Ida in the asteroid belt. The second was discovered around 45 Eugenia in 1998. In 2001, 617 Patroclus and its
Ghost craters on Mercury Mars do not have both tectonic features within their ghost craters, possibly due to the accumulation rates of volcanic material on the Moon and Mars being slower than the rates on Mercury. Ghost craters on Mercury Ghost craters on the planet Mercury have tectonic features such as graben and wrinkle ridges. These features were formed by extensional and contractional forces originating in tectonic processes such as uplift and global contraction. The combination of graben and wrinkle ridges inside ghost craters found on Mercury has not been observed on any of the other terrestrial planets. The tectonic features on Mercury were