Debris from a one-tonne defunct satellite that is heading towards Earth is mostly likely to crash in the ocean or the polar regions, scientists have said.

There had been fears parts of the craft could hit Europe, but experts have now said there is a "very high probability" this would not happen.

The European Space Agency's research satellite will mostly disintegrate as it enters the atmosphere 50 miles above the Earth.

A 200 kg (440 lb) fragment weighing the same as a car engine will survive and will break into smaller debris, it is believed.

The pieces that fall will weigh up to 90 kg (200 lb), said the ESA.

The impact from the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) was likely to take place on Monday.

The GOCE craft weighs around a ton

Italian officials assured residents the risk of debris falling on Italy was now nil, after an earlier warning of "minimal" danger.

"The Italian Space Agency has excluded any impact of fragments from the satellite on Italian territory," the Civil Protection service said.

The ESA claimed humans were 250,000 times more likely to win the lottery than to get hit by the debris.

With a sleek design which led to it being dubbed the "Ferrari of Space", GOCE has mapped variations in Earth's gravity with extreme detail, scientists said.

The data it supplied led scientists to map the boundary between Earth's crust and mantle - called the Moho - and to detect sound waves from the massive earthquake that hit Japan in 2011.

GOCE's mission came to an end when it ran out of fuel and began its descent towards Earth from a height of around 140 miles.