My goodness, what those rovers won't find.
For example, this. (Look at the lower right of the pic)
My first thought - whatever you do, don't lean over it, because man, something might jump out of it and latch onto your space suit's face shield and dissolve it with alien gastric juices and force a squicky ovipositor down your throat and then a few hours later something that looks like a tadpole with teeth will explode through your sternum while you're trying to have a nice dinner.
(Props to this web site for the pic and a very intersting and detailed history of this misunderstood creature.)
What do YOU think it is?