Scientists have devised a new map of the Earth's sea floor using satellite data, revealing massive underwater scars and thousands of previously uncharted sea mountains residing in some of the deepest, most remote reaches of the world's oceans.

'We know much more about the topography of Mars than we know about Earth's sea floor.' -  Dietmar Müller, University of Sydney

The researchers said on Thursday they used gravity measurements of the seafloor from radar equipment aboard the European Space Agency's CryoSat-2 satellite and NASA's Jason-1 satellite to capture underwater geological features in unprecedented detail.

"The pull of gravity reflects the topography and tectonics of the seafloor," said David Sandwell, a geophysicist at Scripps Institution of Oceanography at the University of California, San Diego who led the study.

University of Sydney geophysicist Dietmar Müller, another of the researchers, said about 71 per cent of the Earth's surface is covered by water and roughly 90 per cent of the sea floor is uncharted by survey ships that employ acoustic beams to map the depths.

Seamount corals and brittle stars

Brittle stars and deep-sea corals cover a known seamount in the western Pacific Ocean. Prior to the new map, the vast majority of other seamounts were uncharted. (NOAA)

"We know much more about the topography of Mars than we know about Earth's seafloor," Müller said. "The disappearance of Malaysia Airlines flight MH370 earlier this year has heightened global awareness of the poor knowledge of our ocean depths."

The map reveals major sea floor and sub-sea floor structures. They include a mid-ocean ridge beneath the Gulf of Mexico with a length about equal to the width of Texas as well as another ridge under the South Atlantic west of Angola about 800 kilometres (500 miles) long that was formed just after the continent of South America separated from Africa.

Such "spreading ridges" are cracks in the Earth formed where the planet's tectonic plates moved apart and molten material called magma came up to fill them, the researchers said.

Deciphering Earth's geological past

"Knowing where and when such ridges existed is essential for deciphering planet Earth's geological past," Müller said.

The new map also provides details on thousands of undersea mountains, or seamounts, rising 1.6 kilometres or more from the sea floor, the researchers said. Some are covered by many kilometres of sediments, they said.

In addition to the pure scientific value, the new map could have applications for militaries and for oil exploration, Sandwell said.

Müller said the conclusions the researchers made about seabed topography may be less accurate than acoustic beam methods employed by ships.

"But the global coverage is much better and our method is much cheaper, especially as we are mostly using satellite data that were collected for another purpose," added Müller, who estimated that a complete survey of the deep ocean using ships would cost between $2 billion and $3 billion and would take many years.

CryoSat-2 was dedicated to monitoring changes in the thickness of marine ice floating in the polar oceans and variations in the thickness of the vast ice sheets that overlie Greenland and Antarctica. Jason-1 was dedicated to map the change in the topography of the oceans due to ocean currents.

The study was published in the journal Science.