Planets are big, and we could have missed other landing and habitation sites. ART must have scanned for other air bubbles at some point (I didn’t know what it did in its spare time), but when we first got here it mostly hadn’t given a crap about anything except finding its crew. The kind of mapping scans that would turn up low-impact habitations were usually done by satellite. (Or pathfinders, most of which ART had weaponized.) The planet had no intact satellites, just orbital debris from dead ones, too fragmentary to be identified as Corporation Rim or Pre–Corporation Rim.