TOKYO - Talk about a worst-case scenario.
A rocket engine misfires somewhere over Africa, sending 130 tons of Russian space junk out of a low orbit to rain down on Japan's main island. There is no time to respond, no way to deflect the screaming shards to the ocean where they were intended to go.
The chances of any of this actually happening, the experts say, are 1,000 to one. At worst.
That hasn't kept Japan's government from worrying enough to form a monitoring team and the media from bombarding readers with shrill what-if reports.
"Is Mir's re-entry really safe?" warned a headline this week on the front-page of the Asahi, a major newspaper. Similar stories have been run in other papers and TV networks.
The media attention is causing some jitters.
"The likelihood may be low, but the fact that it is possible is something that people should recognize and be concerned about," said Shunsuke Yamada, a 22-year-old college student.
The Mir space station will be brought back down to Earth in mid-March over the South Pacific between Australia and Chile.
Getting there likely means heading over Siberia, remote parts of China and the Koreas and then 112 miles over the Kansai area in western Japan around March 13. If all goes well, this is the last populated area it is to pass over.
Some 1,500 fragments of 40 pounds or more - the largest could weigh as much as 1,500 pounds - are expected to fall over the target area, which is 120 miles wide by 3,600 miles long.
But a very small error in predicting the trajectory of the debris - an unexpected atmospheric condition, for example - could translate into a significant change in the splashdown locale.
"Even if everything goes well, you can't be sure of where it will be until just 30 minutes before the debris hits," said Yasunori Matogawa, professor of orbital dynamics at Japan's Institute of Space and Astronautical Science.
Moscow's past attempts at disposing of space junk have been spotty.
A Soviet defense satellite plunged out of control and left radioactive debris in the Canadian Arctic in 1978. Mir's predecessor, Salyut 7, fell on the Andes Mountains, causing no damage or injuries but generating fears worldwide in 1991.
The United States has had problems as well. Parts of its Sky Lab smashed into the west Australian desert when it was decommisioned in 1979. Nobody was hurt.
There are perhaps other factors behind the concern.
Relations between Tokyo and Moscow have never been very close. A dispute over several small islands in the North Pacific occupied by Soviet troops in the closing days of World War II has kept them from signing a peace treaty, and a general feeling of distrust between their governments runs deep.
Experts stress the likelihood of Mir doing any damage here is miniscule.
But the aging Mir, launched on Feb. 20, 1986, has suffered several accidents, including a fire in February 1997 and a near fatal collision with an unmanned cargo ship four months later.
That's not very comforting for those under its final path.
Soon after Moscow's announcement of the plan, Foreign Minister Yohei Kono asked the Russian leadership to provide detailed information about how and where Mir was to be brought down.
Tokyo has officially accepted Moscow's response, but has established its own team of experts to monitor Mir, just to be safe.
"All due precautionary measures are being taken," said Noriko Shiomitsu of Japan's science agency.