Skiing Olympus Mons

When I was in high school, my favorite bumper sticker said "Ski Olympus Mons". This proved two things: one, I didn't know much astronomy, and two, I was a huge, huge geek.

Number two hasn't changed much since then, but hopefully the first point has. Olympus Mons is the largest volcano in the solar system, and is located on a large elevated plain on Mars, called the Tharsis shield. Olympus Mons has been extinct for something like a billion years, but when it was active it must have been quite a sight. Unlike the Earth, evidently Mars was not tectonically active, and geologic hot spots tend to sit still in one place. This means volcanos can grow to enormous size. Also, Mars' lower gravity means mountains can be higher there without collapsing under their own weight.

Combine these to produce the mammoth Olympus Mons, 24 kilometers high (compare that to Mt Everest, which is about 9 kilometers high) and 550 kilometers across. That's bigger than the distance of Washington DC to New York City!

So why can't you ski it? If you combine that height with that size, you get an average slope of only about 5 degrees. That's not much of a slope, and the weak Martian gravity would make it hard to get moving. I doubt the resort cities in Colorado have to worry about losing trade just yet anyway.

My thanks to Bill Arnett for pointing out that my original calculation of the slope of Olympus Mons was off by a factor of two, which I have since corrected.