A piece of space trash whipping around in the earth's orbit came perilously close to the International Space Station, forcing six crew members to scatter into an escape vessel while it passed.

The small piece of debris came within a kilometre of the station, and it was travelling fast enough that it could have caused serious damage.

"Definitely, a little too close for comfort," York University space expert Paul Delaney told CTV News Channel.

After Mission Control told the ISS crew about the approaching junk Tuesday around 7:30 a.m. EDT, the six crew members quickly got into their Soyuz capsules and waited. About half an hour later, they were given the all-clear to climb back onboard.

Delaney said that even small hunks of space trash can cause big problems. Even though the debris in question was likely less than 10 centimetres in diameter, it "could have actually caused quite a mess," he said.

The ISS can maneuver if crew are given enough notice, but when such objects are spotted at the last minute, the crew has to be prepared to ditch the station and come back to earth in their capsules.

Delaney said that Tuesday's incident was scary, because "potentially, (we) could lose the entire station, which would be quite disastrous given how long and how much effort its taken us to put it together."

Alternatively, the ISS could have been punctured, with at least one compartment losing pressure.

Delaney suggested that only about two hours of notice was available to the ISS crew Tuesday. About five hours would be necessary to successfully move the station out of danger.

Space junk is a growing problem, as more trips to space result in a growing number of items in orbit. Currently, it's estimated that tens of thousands of items are in orbit, with NASA tracking many of the larger ones.

While some junk gradually slows down and burns up in the earth's atmosphere, more junk is "replenished" as additional space trips leave more garbage behind, he added.

That can also cause problems for the many communications satellites in orbit, which we use for everyday purposes like phones, television and GPS systems on the roads.

"Having space debris impact any of these things can be a massive inconvenience," Delaney said.