The standard demonstration is to immerse a banana in liquid nitrogen at -173 C and then use it to hammer a nail into a piece of softwood. One has to be careful or the banana will shatter.

On Earth, dry ice is in equilibrium with the atmosphere at -78 C, which is not quite so cold as liquid nitrogen, but still enough to stick your tongue irrevocably to a metal spoon.

I haven't yet tried the Mars bar, but this must be part of my "scientific" experiments for next year.

For instance, will the Mars bar penetrate 5-ply wood if thrown from a gas-gun?

Or would a sharpened Mars bar be an appropriate but deniable murder weapon which will not retain finger prints when it melts at body heat?

For answers to this, and more, stay tuned to your favourite "White Mars" channel....