Russia and its partners plan to sink the International Space Station in the Pacific Ocean once it is no longer needed, according to a Russian space official on Wednesday. Expected to be big, old and grubby by 2020, the ISS will be sunk into sea.

"After it completes its existence, we will be forced to sink the ISS. It cannot be left in orbit, it's too complex, too heavy an object, it can leave behind lots of rubbish," said the deputy head of Roskosmos space agency Vitaly Davydov.

Sinking the massive ISS is a countermeasure against the station becoming dangerous space junk. Originally the station was supposed to drop to the ocean by 2015 until the U.S. extended its life cycle to 2020.

Launched in 1998, the International Space Station is a platform for scientific experiments for different space agencies from Russia, the United States, Europe, Japan and Canada. It consists of a dozen modules built by the U.S., Russia, Canada, Japan and the European Space Agency. It is big enough for six residents to live comfortably in space. The ISS was only expected to remain in space for 15 years after which it was to be destroyed in a controlled descent to Earth.

Sinking space stations in order to avoid space junk is nothing new. Russia sank its Mir space station in the Pacific in 2001. America sank Skylab, its first space station in 1979 after six years in space.

Davydov said there are no plans for a new space station after the ISS. He added that a new space station could just be used as a launch pad for further explorations in deep space.

"I cannot rule out that it will be used to put together, create the complexes that in the future will fly to the Moon and Mars," he said, explaining that manned flights are needed for serious exploration.