In the solar system, the number of comets visited by human probes is about the same as that of planets. Most of these detectors fly near comets to collect data. However, in 2005, the "deep impact" probe took the initiative to attack. The impactor released by it collided with comet Temple 1, which is 8km long and 5km wide, at a speed of 10km / s, raising its internal material for the research of instruments on the detector mother ship. The impact left a crater 100 meters in diameter on the comet nucleus.
Comets are frozen materials that hold information about the birth of the solar system. "Deep impact" is to explore the internal materials of comets, uncover the mystery of the formation of comets, and understand the original state of the solar system. In addition, there is increasing evidence that comets and asteroids once brought water and organic matter to the earth, and may even open the evolution of life on earth. Therefore, it also helps to uncover the mystery of the origin of life. Another practical significance of "deep impact" is to accumulate experience for the future. If comets collide with the earth in the future, humans can use spacecraft to place explosive devices, so as to change the orbit of comets to avoid its harm to the earth.