NASA's DART Spacecraft to Purposefully Collide with Asteroid!
NASA has targeted the harmless little asteroid Dimorphos (560 feet in diameter and 11 million miles away) for a head-on collision by their 500-pound DART spacecraft. They will meet at 7:14 on Monday night. The spacecraft is now moving at 14,160 miles per hour, so there will be quite an impact. Remember: force equals mass times the velocity squared.
The experiment will determine if it can be done and if such a collision would have the effect of changing that asteroid’s orbit meaningfully. The reason this matters is that there may be a time when a killer asteroid is on a collision course with Earth and deflecting its path by ramming it over and over again could avert a global catastrophe. The DART mission is the first baby step in building a planetary defense system.
But there’s more. A second, very small companion spacecraft, has been ejected from DART and is now following dutifully three minutes behind. It has two high-resolution cameras aboard and will video the final approach, actual impact, debris thrown out, and the resulting crater. This “personal photographer" spacecraft has limited power so it must slowly relay those great mission pictures to Earth in the days following the collision.
The DART vehicle will also have a high-resolution camera and will be looking right at the target until impact. That video Data will be transmitted to Earth in real-time, but it will be really disappointing. At that speed, the target will be large enough to see for a very short time. Then, of course, nothing. The camera is mainly there to steer DART.
Dimorphous was the chosen target because it is essentially the moon of a much larger companion asteroid, Didymos (2600 feet in diameter). Astronomers have studied this pair for years and know exactly how long Dimorphos's orbit takes. The collision is designed to be head-on, so the expected result will be slowing Dimorphos down by about 1% or several minutes per day. Scientists can easily measure that and determine the actual effect DART had.
Of course, there is always the possibility of a glancing blow … or missing the asteroid altogether. That’s why we do science.
Spoiler: It worked!
