Astronauts aboard the International Space Station were directed to take shelter in their docked spacecraft on Friday and prepare for a possible evacuation after an air leak in the Russian segment of the orbital outpost showed signs of worsening. Nasa mission control instructed the four members of the Crew-12 mission aboard the International Space Station at 9.04 am (local time) on Monday to enter their docked Crew Dragon spacecraft and don their spacesuits as a precautionary measure. The crew, comprised of two American astronauts, one French astronaut, and one Russian cosmonaut, were asked to prepare in case a reported air leak required an emergency evacuation, a Nasa official said, as cited by Reuters.Nasa and Russia’s space agency, Roscosmos, the two principal operators of the International Space Station, have spent months debating the source of and possible remedies for persistent air leaks in Russia’s Zvezda service module, a critical component of the orbiting laboratory.While the leaks had remained relatively minor in recent months, the situation worsened on Monday, with the rate of air loss doubling from about one pound per day to two pounds per day, according to a senior Nasa official. The increase has renewed concerns over the integrity of the module and intensified efforts to identify a long-term solution.The International Space Station is a human-made structure in space that serves as an orbiting laboratory for conducting experiments in low-gravity conditions. It is operated through a partnership involving five space agencies representing 15 countries.The station has been continuously occupied since November 2000 and typically houses a crew of seven. It travels at a speed of about five miles per second and completes 16 orbits of Earth every 24 hours, passing through 16 sunrises and sunsets during that period.The ISS contains living and working areas larger than a six-bedroom house, along with a gym and a 360-degree bay window. Astronauts and cosmonauts based on the station carry out spacewalks to support construction, maintenance and upgrade activities.Its solar array wingspan extends more than 100 metres, and the station contains about eight miles of wiring.