Dactyl is the first moon of an asteroid ever discovered. The names Ida and Dactyl are based on characters in Greek mythology . Rocks from space hit Earth every day. The larger the rock, though, the less often Earth is struck. Many kilograms of space dust pitter to Earth daily.
Larger bits appear initially as a bright meteor .
Significant threats do exist for rocks near 100 meters in diameter, which strike Earth roughly every 1000 years. An object this size could cause significant tidal waves were it to strike an ocean, potentially devastating even distant shores. A collision with a massive asteroid , over 1 km across, is more rare , occurring typically millions of years apart, but could have truly global consequences . Many asteroids remain undiscovered. Such an interplanetary collision would not affect Earth's orbit so much as raise dust that would affect Earth's climate .