Some volcanoes on Venus erupt explosively and spew ash skyward, unlike the planet's typical volcanoes, which gently produce lava flows, the Magellan spacecraft has found.

Although Magellan hasn't yet caught a volcano in the act of erupting, the spacecraft, mapping the cloudy planet, found signs the landscape in three regions is covered by ash from earlier volcanic blasts.Those blasts were roughly comparable to ash eruptions from Alaska's Redoubt Volcano or Mount Vesuvius in southern Italy, John Guest, a geologist from University College London, said Wednesday.

"If an eruption like this occurred on Vesuvius, you'd put a layer of ash all over Naples," said Guest, who is working on the Magellan mission at the National Aeronautics and Space Administration's Jet Propulsion Laboratory.

Magellan's pictures of the Guinevere Plains and two other regions show volcanoes surrounded by cracked and faulted landscape, some of which is covered by sand-sized grains of volcanic ash, Guest said.