I heard Prof Pillinger (Beagle 2 notoriety) on Sky last night.
He was basically saying that there was no way that either of the
NASA rovers would be able to determine whether life had or
currently existed on Mars.

While he is right in that neither rover has life detecting instruments;
he forgot that fossils are top drawer evidence of past life. A tiny
fossil would show up on the microscopic imager, if it was contained
in bedrock being analysed. So to say that the Nasa rovers can
in no way determine whether life once existed, is complete bull****.
Sure, it would be bloody lucky to come across a fossil, even if they
exist, but it is feasible.