Scientists from the Institute for Computational Cosmology and Department of Earth Sciences at Durham University have unveiled a new map of an ancient volcano on the Moon that erupted over 3.5 billion years ago, showing that the explosive eruption spread debris over an area much greater than previously believed.

The team of astronomers and geologists studied an area of the lunar surface in the Compton-Belkovich Volcanic Complex, using data from NASA's Lunar Prospector spacecraft, which had spotted the volcano on the Moon's far-side 15 years back. Even after its discovery, scientists found it difficult to study the volcano as it is hidden beneath debris from meteorite impacts. However, NASA's Lunar Prospector detected gamma rays emitted by the thorium that is capable of passing through up to a meter of rock.

Using this information, the scientists adopted a "pixon" image enhancement technique, which had been originally designed to look deep into the distant Universe. The sharper map revealed the enormous size of the thorium deposit from the volcanic eruption.

By mapping the radioactive element thorium thrown out during the eruption, the scientists found that Moon's low gravity had helped the debris from the unnamed volcano cover an area the size of Scotland equivalent to about 70,000km. According to the research team, the eruption spewed out rock five times further than the pyroclastic flow of molten rock and hot gases that had buried the Roman city of Pompeii.

The scientists now plan to apply the same mapping technique to study the largest known volcano in the Solar system, Olympus Mons on Mars. But this time, instead of the radioactive element thorium, the researchers will search for hydrogen and any possible remnants of water ice from glaciers on the high slopes of Mars.