Debris from a defunct six-tonne NASA science satellite that crashed to Earth on Saturday fell harmlessly in a remote area of the South Pacific Ocean, NASA said on Tuesday.

Experts estimated that as much as 1,100 pounds (495 kg) of debris survived the bus-sized satellite's fiery plunge through the atmosphere, which started at midnight EDT on Saturday (0400 GMT on Sunday).

The Joint Space Operations Center at Vandenberg Air Force Base in California determined that the U.S. space agency's Upper Atmosphere Research Satellite (UARS) entered the atmosphere over the Pacific Ocean at 14.1 degrees south latitude and 170.2 west longitude, NASA said in a statement.

That location is in Pacific in the rough vicinity of Samoa. The debris was then scattered between 300 miles and 800 miles (480 km to 1,300 km) from the re-entry point, NASA said.

This location is over a broad, remote ocean area in the Southern Hemisphere, far from any major land mass, NASA said, adding that the agency is not aware of any possible debris sightings from this geographic area.

Measuring 35 feet long and 15 feet in diameter (10.6 metres long and 4.6 metres in diameter), UARS was among the largest spacecraft to plummet uncontrollably through the atmosphere.

NASA now plans for the controlled re-entry of large spacecraft, but it did not when UARS was designed.

The 13,000-pound (5,897 kg) satellite was placed into orbit by a space shuttle crew in 1991 to study ozone and other chemicals in Earth's atmosphere. It completed its mission in 2005 and had been slowly losing altitude ever since, pulled by the planet's gravity.

UARS was one of about 20,000 pieces of space debris in orbit around Earth. Something the size of UARS falls back into the atmosphere about once a year.