Since Sputnik first orbited Earth, mankind has shot into space thousands of tons of hi-tech gubbins. Much still streaks through the firmament as so-called "space junk". Now a US rocket company is offering the highest bidder the chance to lob a package onto the Moon. Are we guilty of interplanetary littering?
By Ryan Dilley
BBC News Online Magazine
"If anyone argues that we are spoiling the Moon, then their concerns are misplaced," says Gregory Nemitz of Orbital Development, the company which is auctioning on eBay the chance to crash 20kg of cargo of your choosing into the lunar surface at 4,000mph.
"The impact crater will be 500ft in diameter, that's a pinprick. The moon is just a huge dead rock."
Mr Nemitz hopes the project, using a Russian missile, will kick-start a new era of commercial activity in space.
Those interested in bankrolling the $6m moon shot include someone whom Mr Nemitz suspects of wanting to consign the ashes of a deceased relative to an extraterrestrial grave. "My ideal customer," says Mr Nemitz. "The dead can't complain."
Mr Nemitz's rocket - plus the urn, or whatever 20kg item is placed in the nosecone - is hardly likely to cause more than a minor blemish on the Moon's surface.
However, just as the exploration and commercial exploitation of our seas has left flotsam and jetsam in its wake, the more recent conquest of space has also produced a trail of debris.
See your stuff land here!
This discarded material is so numerous that it even obscures astronomers' views of the heavens, says Dr Amos Storkey of Edinburgh University, who helps stargazers sort the wheat from the chaff.
"There are in the order of 1,000 to 10,000 objects in the direction you are looking in. That is a big issue, since an astronomer may think they are looking at a galaxy, when in fact it is space junk."
Lost in space
There may be as many as 110,000 loose objects 1cm wide or greater hurtling around within 1,200 miles of Earth.
The items range from whole broken-down satellites to bolts - and even a glove lost by the US astronaut Edward White during a 1965 spacewalk.
This assorted space junk can travel at phenomenal speeds - 18,000mph if it orbits 600 miles above Earth - and can do phenomenal damage if it strikes anything.
A floating rubbish bag once halted a Mir docking
In 1996, a French satellite was fatally hit by a chunk of an exploded Ariane rocket. Parts of the shredded satellite, in turn, added to the shroud of debris surrounding our planet.
This collision - the first such instance reported - prompted newspaper headline writers to suggest that "space junk could close final frontier".
However, Professor Hans Haubold, of the UN Office for Outer Space Affairs, says space debris has not claimed any more active satellites or manned craft.
"But as more countries are launching satellites, the density of debris is increasing," he says.
To add to the clutter, China and the US have also both vowed to launch ambitious manned missions. This week US experts are meeting to mull over President Bush's pledge to "lift [the] national spirit" by putting astronauts on Mars.
Professor Haubold says that all nations with an interest in space exploration are concerned about the proliferation of space junk.
Currently, early warning systems allow most spacecraft to be steered clear of larger chunks of approaching debris.
But the impact of smaller particles can do cumulative damage to hulls. During the 1990s, for instance, the space shuttles' windows had to be replaced with growing frequency.
Watch out for splinters
More worryingly, even a tiny speck of metal could breach a space suit - something which prompts spacewalking astronauts to stay shielded in the shadow of their craft.
"At present it is very difficult to remove this debris. A craft would have to be sent up to collect it, and that would be so expensive as to make it impractical," says Professor Haubold.
"The only sensible options are to make sturdy, reusable craft which return to Earth once their mission is over, and to launch as few craft as possible."
The UN has drawn up a best practice guide for building spacecraft which shed fewer parts, move off to a safe altitude once their work is done, or are guided earthward to burn up in the atmosphere or splash down harmlessly in the sea. Of course, all this adds cost.
But work is being done on ways to deal with the junk already in situ. Nasa has been linked to an Earth-based laser to push debris to up to safety or down to destruction.
Nasa likes hard landings too
This plan - although far off - horrifies the Australian archaeologist Dr Alice Gorman. She heads a campaign to protect space junk, arguing that some of the celestial flotsam is of great historical value.
But even Nasa sees the silver lining of some space junk. In 2002, a bus-sized portion of what was thought to be an Apollo mission rocket was spotted by amateur astronomers.
Estimates that it could smack into the Moon caused great excitement, since previous planned impacts of rocket parts allowed Nasa to measure the shockwaves passing through the Moon and find out more about what lies beneath the surface.
J002E3, as the object was called, actually skimmed past the Moon before whizzing back out into deeper space, disappointing the scientists. So perhaps, they at least will be quite keen to see Mr Nemitz's rocket and cargo complete the one-way journey.