"the little protuberance is probably about 0.5 cm tall, or even smaller."
Five mm is obviously tiny. Keep this in mind before making up hypotheses as to what the thing is. =) We have to wait until better data is available.
What's fascinating in itself though is that no person, however sceptical, can immediately rule out the possibility that stuff like this is some form of life or even evidence of non-human technology. Of course, such hypotheses have to work extremely hard before they should be accepted. Our standards of evidence for stuff like this must always remain as high as possible, given the emotions and mass misunderstandings involved. But the very fact that we've come this far and still cannot rule out the existence of life on Mars is quite remarkable.