Fark linked up this space.com story detailing an interesting speculation about the red planet:

Sulfur, acids, magnesium, iron -- all put together under the carbon dioxide-rich skies of Mars -- could just reek.
...
[Jim Garvin, NASA Lead Scientist for Mars and Lunar Exploration] said on his field excursions here on Earth to volcanic areas, the sulfurous stench to him is a kind of cleansing smell. "I don't know. It may stink in the eye of the smelling beholder," he told SPACE.com .

Personally, I agree with the guy. Sulfur smells have been a little surprising at times, but I've never thought they stink. The contents of my daughter's diaper pail, now that's a stink!