Space: the next frontier: it's a relatively young category, but outer space memorabilia may be prepared to blast off.(TRENDS)

The backpack that Apollo 15 astronaut James B. Irwin wore on the moon containing oxygen to keep him alive would have been a nice souvenir. But it was designed to be disposable, so it was jettisoned on the lunar surface, left behind during the July 1971 mission. Looking for another memento to bring back with him, Irwin managed to cut loose a moon-dust saturated patch from the backpack's cover.

His family is glad he did.

That patch was one of two lots of Irwin's personal items that were sold through Christie's by his family in 1999 and 2001 for a combined $500,000.

Even though those sales happened several years ago, they reflect the fervor that collectors have for objects that have slipped the bonds of earth and, in some cases, touched an alien world. Collecting space artifacts as well as coins, stamps, and medallions commemorating the U.S. and Soviet space programs has been a cyclical hobby since the late 1960s when the race to the moon captivated the public and helped create the genre.

Robert Pearlman, who runs a Web site devoted to space collecting called, naturally, CollectSpace.com, says he has seen an increase in interest recently as talk of a return to the moon--and eventually to Mars--heats up in his home town of Houston, headquarters of the Johnson Space Center.

And, Pearlman says, people are getting into the hobby at a lot of different levels.

"The nice thing about space memorabilia is that it spans all the other genres of collecting--coins, stamps, cards--but also distinguishes itself by offering collectors a chance to own things actually used in space or on space training missions," he notes.