Finding the North on Mars

[martins]

So... any options for doing this with a towel?

I haven't got my copy of the Guide to hand, but this should be fairly obvious:

1. Ensure approximately uniform anaerobic microbial growth throughout the towel (generally a given for hitchhiking towels)
2. Moisten towel
3. Drape over a rock of suitable size, covering all sides
4. Wait a few days
5. North is the side with highest bacterial population density (northern hemisphere only, obviously)

 

[Arvil]

Moss on the pole facing side of trees? Oh, wait, no trees, just that stick.