Moon's ancient giant volcanic eruption decoded

Scientists have produced a new map of the Moon's most unusual volcano, showing that its explosive eruption spread debris over an area much greater than thought.

A team of astronomers and geologists at Durham University studied an area of the lunar surface in the Compton-Belkovich Volcanic Complex.

By mapping the radioactive element thorium which spewed out during the eruption, astronomers discovered that assisted by the Moon's low gravity, debris from the unnamed volcano was able to cover an area the size of Scotland.

The eruption, which happened 3.5 billion years ago, threw rock five times further than the pyroclastic flow of molten rock and hot gases that buried the Roman city of Pompeii.

The team used data from NASA's Lunar Prospector spacecraft that first spotted the volcanic site in 1999 when it detected an isolated deposit of thorium.

The team used a "pixon" image enhancement technique, originally designed to peer into the distant Universe, to sharpen the map and reveal the enormous size of the thorium deposit from the volcanic eruption.

"Volcanoes were common in the early life of the Moon and in fact the dark 'seas' you can observe on the lunar surface were created by runny, iron-rich, lava that flooded large areas, filling in impact craters and low-lying ground," said Jack Wilson from Durham University, who presented the study at 46th Lunar and Planetary Science Conference in Texas.

"By mapping the radioactive content of the lava from this volcano we have been able to show that molten, radioactive rock was thrown far beyond the slopes of the volcano, reaching several hundred miles in one direction," Wilson pointed out.

The team is now planning to apply its mapping technique to the largest known volcano in the Solar system, Olympus Mons on Mars.