First off I'm pretty sure I got more brains than a rock, seeing as how a rock is inanimate and non-living and all.

Secondly I doubt we'll make it to mars, not this time around anyway. Mars would require a massive investment of resources, perhaps more than anything else ever before in the history of humanity. Don't think we got the discipline to pull that now.

The moon on the other hand is a known quantity, we know exactly what we're getting ourselves into here. Been there done that, the moon may also possess exploitable resources, making it an even better target, in addition to an easy target. A permanent off planet colony could be established within a decade, with material returns on the investment not long after becoming firmly established.

Not only that but the moon is safer, a crew en-route to, or already on it, is not beyond the abilty to rescue. A mars mission however would be.