 We'll end our segment on comets with a look at two of them that changed our thinking and our capabilities when it comes to these objects. In 1994, the comet Shoemaker-Levy collided with Jupiter. The first impact occurred at 2013 on July 16 when Fragment A of the nucleus entered Jupiter's southern hemisphere at a speed of about 60 km per second, that's 37 miles per second. Instruments on the nearby Galileo spacecraft detected a fireball plume that reached a height of almost 3,200 km, that's 2,000 miles. Remember that our atmosphere extends only a few hundred kilometers above us. Observers soon saw a huge dark spot after the first impact, 6,000 km wide. Over the next six days, 21 distinct impacts were observed, with the largest occurring on July 18. This impact created a giant dark spot larger than the Earth. Jupiter absorbed them all. The changes to the planet were dramatic but disappeared after a few months. But if Shoemaker-Levy had hit the Earth instead of Jupiter, it would have wiped us out. This highlighted, for everyone, the importance of understanding comets and asteroids and how to change their trajectory should we ever find one this size heading our way. Progress in this area has been made.