Trouble has once again stuck the International Space Station, this time in the form of a coolant leak. Astronauts aboard the orbiting laboratory noticed white flecks floating off the exterior earlier today. The flecks, which are frozen ammonia, appear to be leaking out of the cooling system for one on the giant solar panels which provide power to the station. As much as 75% of the panel's coolant may have already leaked out.
Although this is a serious situation, it's not the first coolant trouble the ISS has faced. A panel, likely the same one now leaking, underwent repairs via spacewalk last year. It might seem strange that you'd need coolant in space, but the solar panels must dissipate the tremendous energy of the sunlight they collect. Solar panels are the primary power source for the station - losing all of them would probably force the astronauts to return home via their docked capsules. To prevent this, mission controllers plan to isolate and shut off this particular panel if the leak cannot be controlled.
If the previously-repaired panel is indeed leaking, a more comprehensive fix will need to be designed and sent up via unmanned capsule. Spacewalking astronauts would then implement the solution, restoring the station to full health. Such a procedure could take months to design.