I was headed North on I-5 when I saw a glowing green object streaking across the night sky and descending towards Tualatin.I was headed north on I-5, and had just passed the North Wilsonville exit. I was travelling at approx. 70 mph. Just past the exit, the highway inclines for a ways, then flattens, and then descends down into a valley. The Tualatin exit is at the bottom of the valley. As I began to level out after the incline, I noticed a greenish glowing object streaking across the sky. The object was also headed north, but was travelling faster than me, and appeared to be on a downward path. I don't know how high up in the sky it was...maybe 200-300 feet? I don't really have any reference point to provide a good estimate. It was fairly large, however, and for a moment (because of the whole terrorist scares around the world) wondered if this were a missile about to hit. It was somewhat spherical, or ovular, almost reminiscent of a comet, but I didn't think to pay very close attention to the shape. The object's speed was constant, and it descended down into the valley (mentioned above). I fully expected to see/hear an explosion of some sort, as it was descending very quickly, but nothing happened. I was still too far back to see down into the valley, so I lost sight of it once it went below the top of the hill. When I began heading down towards the Tualatin exit, I couldn't find the object anywhere in the sky. And there didn't appear to be a crash of some sort (no burning buildings, etc.). So, I have no idea what happened to it, or what it was. The duration of time wasn't any longer than 5 seconds or so from the time I noticed it and the time it vanished. I didn't see anything mentioned on the late night news, nor in the newspaper this morning, so I searched the web to see if something was posted about it . I couldn't find anything, but I found this site. So, I'm now just wondering if anyone else saw it and possibly what happened to it once it reached Tualatin.