2012). Historically space anemia has been explained by a number of possible mechanisms: decreased erythropoietin (EPO) production, erythropoietic suppression, sequestration, blood loss, and enhanced hemolysis (Tavassoli 1982). One group suggested rapid destruction of young erythrocytes (neocytolysis) to resolve hemoconcentration in space, descent from altitude, withdrawal from EPO administration, and renal disease (Alfrey et al. 1996, 1997; Rice et al. 1999, 2001; Chang et al. 2009; Pottgiesser et al. 2012). Franco (2009) pointed out that the evidence for neocytolysis was indirect. Here, EPO is linked to anemia.