The world's two largest radio telescopes have combined to peer beneath the perpetual cloud cover of Venus to reveal new details of the planet's surface.

Radio pulses were transmitted from the Arecibo radio telescope in Puerto Rico, bounced off Venus, and then picked up again by both the Arecibo and the new Robert C Byrd Green Bank Telescope (GBT) in West Virginia, US.

Only radar can see what lies underneath the brilliant white clouds that permanently cover the second planet out from the Sun.

And astronomers say that the combination of the GBT, the world's largest fully steerable radio dish, and the Arecibo dish, the world's most powerful radar, makes for an unmatched tool for studying Venus and other Solar System objects.

Active planet

"Having a really big telescope like the new Green Bank Telescope to receive the radar echoes from small asteroids that are really close to the Earth and from very distant objects like Titan, the large moon of Saturn, will be a real boon to radar studies of the Solar System," said Professor Donald Campbell, of Cornell University.