 Niger's military leader has ruled out rejoining the West African regional bloc ECOWAS. General Abderrahman Chiani was speaking at the first meeting of a new grouping made up of Niger, Burkina Faso and Mali, the alliance of Sahel states. Four volunteers are preparing to leave a small compound in Texas where they've spent more than a year in conditions simulating those on Mars. The American Space Agency, NASA, will want to find out how they've coped with their isolation.