AN ITSY-BITSY spider went missing this week.

The creature was supposed to be aboard the International Space Station weaving a web for science, so if you've found it please contact NASA in Washington.

Researchers at NASA had recruited two orb spiders - apparently the term itsy-bitsy has fallen from favour - for an experiment into whether the arachnids could spin their webs in zero gravity.

In fact, they failed miserably.

The normally symmetrical webs were a jumbled mess worthy of no self-respecting spider and unlikely to snare any passing astronauts.

But embarrassment may not be the reason why one of the spiders has gone absent without leave. More on that in a moment.

The web failure coincides with the arrival of a large shipment of supplies from Earth, meant to replenish the space station and make way for more people to live aboard the spacecraft.

When the renovations are complete, the orbiting home will have six bedrooms - and views that will take your breath away, especially if you step outside.

Aside from a refrigerator, kitchenette and sleeping compartments, the 6300 kilograms of home improvement gear included an extra toilet and a new recycling system for converting urine into drinking water.

As one of the astronauts-cum-couriers who delivered the crate to the Space Station said, it "will make yesterday's coffee into today's coffee".

Over the years, NASA has spent considerable time working on the issue of recycling pee, and it's no simple task. In the days of the Mercury, Gemini and Apollo programs, astronauts took their own supplies of air and water from Earth. For longer stays, though, recycling is essential.

To reuse water, the basic technique is to cook the urine until the water separates as steam and rises so it can be captured. But there's a problem, and it's the same one the orb spiders faced: zero gravity.

On Earth, steam rises because it weighs less than water. In space, everything is weightless.