some of it i already knew : roanoke was a class six planet , which meant ( and here i 'm double-checking with the colonial union department of colonization protocol document , get it wherever pdas have access to a network ) that the planet was within fifteen percent of earth standard gravity , atmosphere , temperature and rotation , but that the biosphere was not compatible with human biology - which is to say if you ate something there , it 'd probably make you vomit your guts out if it did n't kill you outright .