Snapshots from Atlas 5 launch

Eric Boe, one of three astronauts assigned to the first piloted test flight of a Boeing CST-100 Starliner commercial crew ship later this year has been removed from the mission due to unspecified medical issues, NASA announced Tuesday. He will be replaced by veteran astronaut Mike Fincke.

United Launch Alliance called off the planned launch of an Atlas 5 rocket Wednesday at Cape Canaveral to resolve a problem with valves at the launch pad, while a SpaceX team a mile-and-a-half to the south readied a Falcon 9 rocket for liftoff Thursday evening with a GPS navigation satellite for the U.S. military.

After years of analyses and debate, NASA announced Monday that the agency’s next Mars rover will land on or near an ancient river delta where water once flowed into a 30-mile-wide, 1,600-foot-deep crater to search for signs of ancient microbial life and to continue ongoing studies of the red planet’s history and evolution.