A friend and I were driving down to Iowa City, Iowa. We were heading south on Interstate 380 and up in the clouds in front of us we saw a big green ball of light. It was definitely moving, and very large. It had a tail on it, much like a comet. When I first saw it, my first thought was that it looked just like a comet, but then I remembered how close it was to Earth. It only lasted about 5 seconds, and then it was completely gone. It disappeared just as fast as it showed up. I definitely got the chills after I saw it, it was very very strange.