Probe makes unintended splash.

A Russian probe bound for Mars and carrying 200 grams of plutonium crashed into the South Pacific minutes after its launch on Nov. 16. Although the submerged plutonium does not appear to pose a threat, some worry that the cash-strapped, understaffed Russian space program may have hit bottom.

The Russian space agency reported that the fourth-stage booster engine of the probe, Mars '96, misfired. Space policy analyst Marcia S. Smith of the Congressional Research Service in Washington, D.C., says it's unclear whether the crash stemmed from a rocket malfunction or a failure of the craft to command the fourth-stage engine to fire.

U.S. officials who thought they were tracking the plutonium-bearing probe issued a warning on Nov. 17 that Mars '96 might hit Australia. In fact, the probe had already gone to its watery grave a day earlier, and the U.S. team was monitoring remnants of the detached rocket engine, Russian scientists said.

Mars '96 featured four landers, including two designed to penetrate the Martian surface. Landers won't fly again until 2001, when NASA's Mars Surveyor 2 is slated for launch. Russian participation in that flight is now less certain. If the Russians don't fly a follow-up probe scheduled for 1998, it might be difficult for them to retain scientists and engineers until 2001, Smith says.

Russian scientists have conceded that time and money constraints prevented them from fully testing the 22 scientific instruments on Mars '96. Whether that extended to an incomplete evaluation of the craft and its rocket remains to be seen, says Louis D. Friedman of the Planetary Society in Pasadena, Calif.