NASA will let the International Space Station (ISS) plummet back to Earth in 2031.

After 32 years of space station construction, experiments, photography and human habitation, the iconic piece of space infrastructure will be nudged out of its orbit to meet its watery demise. 

NASA recently extended the space station's operations from 2024 to 2030, but the plan includes an end date for the ISS; the most expensive object ever built. 

The US and Russia launched a plan to build the ISS together in 1993, with Japanese, Canadian and European space agencies signing on later.

The Zarya Control Module - the first segment of the space station - launched aboard a Russian Proton rocket in 1998.

In the years since, tonnes of parts have been added, removed and replaced. However, the space station was never meant to be a permanent installation. 

A big part of the reason for its retirement is that it is too difficult to clean. A range of bacteria, fungi and other microbes live on the station, and are exceedingly difficult to wipe out. 

Additionally, the outer surfaces of the ISS are becoming worn too.

Objects below about 500km from Earth naturally fall back to the surface, so the space station is frequently boosted back up to counter this effect. To bring it back down, its operators will send it into a controlled descent using thrusters, gradually putting it on course for its eventual crash.

It will be submerged in a patch of water dubbed the ‘spacecraft cemetery’, or the South Pacific Oceanic Uninhabited Area.

Replacements are being planned, with Russia to deploy the Russian Orbital Service Station in five or six years' time.

China has already launched the first part of Tiangong, with more components going up soon. 

NASA has given a private firm, Axiom Space, permission to attach modules to the ISS, which will eventually detach to become their own low-Earth orbit facility.