Last month, we became accustomed to seeing daily more riveting images of a huge, upside-down-pear-shaped bag: now rising from the Moroccan desert, now sailing over the Himalayas, now poised photogenically above Mount Fuji.

This week and next, if the weather in Central Australia finally cooperates, people in the Southern Hemisphere should be able to look up on clear nights and see a phantom form, rather like an inverted pendulous jellyfish, crossing the face of the moon.

The former apparition was, of course, the ill-fated Virgin ICO Global Challenger on its quest to complete the first nonstop round-the-world balloon flight. (Delayed at the Chinese border, the balloon missed a date with the jet stream and was forced to ditch in the Pacific on Dec. 25, well short of its goal.) The latter will be the giant Team RE/MAX balloon now scheduled to be launched Tuesday, after weeks of delay, in pursuit of the same aim. This mission, even if it fails, is mind-boggling: The pilots will ride in a capsule beneath a gas-filled globe bigger than the Houston Astrodome and made of clear plastic as thin as a dry-cleaning bag. What is more, the balloon will fly at an altitude of some 39,000 meters, more than four times higher than commercial jets, in the black silence near the top of the stratosphere where Earth's layers end and space begins.