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
Craters of the Moon National Monument and Preserve some birds also alter their times of activity. Some animals, like ground squirrels and marmots, have one or more periods of estivation, a summer hibernation that allows them to avoid the hottest and driest periods. Several animals are unique to Craters of the Moon and the surrounding area. Subspecies of Great Basin pocket mouse, American pika, yellow-pine chipmunk, and yellow-bellied marmot are found nowhere else. Lava tube beetles and many other cave animals are found only in the lava tubes of eastern Idaho. In May 1980 wildlife researcher Brad Griffith of the University of Idaho started a three-year study to