eugene shoemaker is a hail of bullets as he called the universe in terms of what is going on out there. the point is * come in all shapes and sizes. robo piles of part of it. so it varies according to which one you are talking about. the answer is we don't know enough. that is why arrows, that mission a few years ago worked. and the japanese did the same thing. to try and get as much information as possible about our neighbors. >> host: so does that mean that if we see one coming at us the first thing we have to do is send a mission to to find that what is like? >> guest: it depends upon how close it is. it is 11:00. no. then you go any way that you can. if it is far away that would be a smart thing to do, find out what it is. in addition to everything else the science builds up. plantings. that is what is important. again, it is a matter of how close it is. >> host: right. how big and how close to something have to be when the only thing left? >> guest: that is a good question, too. depends not only on its size by what it is made of. my suspicion is that within five or six years that