Without being an expert, I would say that samples on Earth would let us (or at least those who look at the samples) look in ways the rover was not designed to l

Without being an expert, I would say that samples on Earth would let us (or at least those who look at the samples) look in ways the rover was not designed to look. There is a lot of analytic equipment that is here on Earth but not on Mars. Also, there are things to study besides past life. Geology, material science, horticultural implications, and other things are all worth study The "past life on Mars" maybe interesting but it is also an easy selling point.