SPACE PROBE CRASHES IN PACIFIC.

Byline: Todd S. Purdum The New York Times

The remnants of an unmanned Russian space probe that failed to break out of Earth's orbit re-entered the atmosphere above the southern Pacific Ocean west of South America shortly after 5:30 p.m. Pacific standard time Sunday night and apparently crashed into the sea, American officials said.

White House aides traveling with President Clinton in Hawaii on his way to a state visit in Australia originally feared that debris from the Mars-bound probe could fall to land someplace in east central Australia. The probe carried a small amount of radioactive plutonium in energy packs powering vehicles intended to land on Mars.

But officials said the plutonium, about 200 grams of pellets the size of pencil erasers held in heat-proof metal containers the size of 35-millimeter film canisters, posed no threat if it fell away from populated areas. The battery packs were among the few parts of the 7-ton probe expected to survive re-entry into the atmosphere.

A statement from the U.S. Space Command in Colorado Springs, Colo., said that the probe was believed to have re-entered the atmosphere in ``a broad ocean area west of Chile'' and that if any debris survived, it might have fallen into the ocean several hundred miles away. A senior White House official in Hawaii said it appeared that the debris had broken through the atmosphere about 1,500 miles west of Peru.

The probe failed to leave Earth orbit early Sunday morning when booster rockets intended to push it beyond the orbit misfired. Satellites from the U.S. Space Command monitored its progress.

But just after 5 p.m. PST, Robert Bell, the National Security Council's senior director for defense policy, told Cable News Network in Washington that ``we have some very good, late-breaking news'' that whatever debris remained after the probe pierced the atmosphere appeared likely to land harmlessly in the Pacific Ocean.

Russian space officials confirmed the American report Sunday night of the spacecraft's fall toward Earth, but would add no details.

Earlier Sunday, officials of the Space Communication Center in Yevpatoriya, Ukraine, said they had lost contact with the Mars 96 spacecraft Sunday morning a few hours after it lifted off from the Baikonur space center in Kazakstan.

John Pike, head of space policy at the Federation of American Scientists, a private group in Washington, said the amount of plutonium involved in Mars 96 was not a cause for alarm. ``On a scale of 1 to 10,'' he said, ``this is a 1.''

He said the dangers paled next to an incident in 1978, when the radioactive remains of a Russian satellite fell into northern Canada and forced the Canadian authorities to spend millions of dollars to clean it up.