With the prospects for finding life at Mars looking up, proponents of elaborate human settlements there are ready to defend themselves against charges of contaminating what’s possibly already thriving there. And so-called terraforming advocates already have some scientists on their side, offering up data and theories that can be used to bolster the case for transforming the Red Planet into an Earth II. Tantalizing images returned in the past 18 months from robotic probes have shown Mars to be an astounding planet. Liquid water may have been active in recent geologic times, suggesting that past and even present life on Mars is a decent bet.