My name's Eric Loberg, director of the Taylor Planetarium here at the Museum of the Rockies, and I was going to discuss what passed by Mars. Lots of things pass by Mars like asteroids. There's the asteroid belt between Mars and Jupiter but some of them, the amor asteroids actually cross Mars's orbit, and so once in a while they'll pass right by Mars. Other things that can pass by Mars are spacecraft, and so sometimes we'll use Mars as a gravity assist, and if this was the planet Mars and a little spacecraft, we'll actually shoot these right by the planet Mars and they'll speed up a little as they go by, and that way we can have a little bit of a faster boost into space when we go past Mars. We haven't done that in a little while, so probably if you've heard of something passed by Mars it was a comet. Comets come from the oort cloud, and an oort cloud is very very far out in space, lots and lots of dust and rock way out there, they're shooting from every direction in the distant regions of space out into our solar system, and when they get to our inner solar system, sometimes they'll pass by the planets. They've passed by the planet Mars, and one did recently called the comet ISON, the comet ISON passed by Mars at relatively close. So the distance between Mars and ISON if we multiply that 0.07 astronomical units times the number of the astronomical units ends up being ten million five hundred thousand kilometers, which is still a long ways out there in space. This distance for example is about 27 times the distance of the earth to the moon. So ISON was much much farther away from Mars then the earth is from the moon. Or we could look at it as wide as the sun is. The sun is many many times bigger than earth. You could stack 100 earths right across the sun. The sun's very big, and this would still be about 7 sun widths, if you could stack 7 times the sun, one next to the other to the other, that would still the distance from ISON on one end to Mars on the other end. This is still a relatively close distance in space, often objects just don't pass near each other. Once in a while we'll be passed by here on earth little tiny asteroids, to have a big comet like ISON pass this nearby would I suppose make us a little nervous, eventually comets will probably hit Mars and hit the Earth again, but that may be billions to billions of years in the future, we just don't know. So, what passed near the planet Mars? Probably the comet ISON. Comets pass by once in a while, comet ISON was relatively close to Mars, and that's likely what you heard passing near Mars recently. My name's Eric Loberg for the Museum of the Rockies Taylor Planetarium.