VIDEO: Expedition 42-43 mission preview

Two NASA astronauts and an Italian flight engineer are sheltering in the space station’s Russian segment as mission control analyzes a possible leak of toxic ammonia coolant aboard the complex.

A Russian Progress supply ship packed with 3.1 tons of cargo and propellant to refuel the International Space Station is set for liftoff Tuesday from the Baikonur Cosmodrome in Kazakhstan.

Astronauts Butch Wilmore and Terry Virts suited up and ventured outside the International Space Station on Sunday on their third spacewalk in eight days to install equipment to help future commercial crew capsules built by Boeing and SpaceX navigate to the complex.