BV5721 - Southern stars trail the celestial pole in this long exposure image. In the foreground are petroglyphs engraved in the rock by ancient Atacameno people. Hierbas Buenas rock art site is located in the Rainbow Valley, near San Pedro de Atacama, in the Atacama Desert, Chile.
JC7467 - An illustration of multiple sclerosis, an autoimmune disease that damages the central nervous system and leads to muscle spasms, loss of balance and coordination, numbness, and muscle weakness. In MS patients, myelin reactive T-cells cross the blood brain barrier and bind to antigen presenting cells in the brain. This results in a release of pro-inflammatory cytokines which damage myelin sheaths and the cells responsible for producing myelin (oligodendrocytes).