The fragments fell 775 miles west of Wellington Island, showering debris over the southern Pacific.
The Phobos-Ground was designed to land on Phobos, one of Mars' two moons, and return to earth with soil samples.
The probe was one of the heaviest and most toxic space junk to ever crash to Earth. Space officials and experts said the risks of the crash were minimal, however, because the toxic rocket fuel and most of the craft's structure burned up in the atmosphere.
Phobos-Ground, a $170 million project, has been called Russia's most expensive and ambitious space mission since the Soviet era.
The Associated Press contributed to this report.