A new computer model finds that heat in Venus' hot atmosphere could have led to a cooling effect within the planet's interior.

Venus is often nicknamed Earth's evil twin because although it is a similar size to Earth, it is shrouded in a thick, inhospitable atmosphere that is considered an extreme form of the greenhouse effect, created by carbon dioxide, sulphur dioxide and water vapour spewed out from thousands of volcanoes in Venus' youth. Today's surface temperature of 470 degrees Celsius, forced by this extreme greenhouse effect, could have been a lot higher in the past.

Much of a planet's heat originates from within its interior, through the radioactive decay of elements and from the left-over heat of planetary formation. In Venus' case there is enough heat to partially melt portions of the upper mantle, which rise up to penetrate the crust at volcanic vents, extruding lava onto the surface and gases into the atmosphere.

The more greenhouse gases the hotter the atmosphere, and one might expect that to lead to more volcanism. "But at a certain point this process turned on its head – the high temperatures caused a partial mobilization of the Venusian crust, leading to an efficient cooling of the mantle, and the volcanism strongly decreased," says lead author Lena Noack from the German Aerospace Center (DLR) in Berlin. "This resulted in lower surface temperatures, rather comparable to today’s temperature on Venus, and the mobilization of the surface stopped.”

Noack and colleague Doris Breuer arrived at this conclusion by constructing a model that described Venus' hot atmosphere as ‘coupled’ to a 3D model of the planet’s interior.

“Interestingly, due to the rising surface temperatures, the surface is mobilized and the insulating effect of the crust diminishes,” says Noack. “The mantle of Venus loses much of its thermal energy to the outside. It’s a little bit like lifting the lid on the mantle: the interior of Venus suddenly cools very efficiently and the rate of volcanism ceases. Our model shows that after that ‘hot’ era of volcanism, the slow-down of volcanism leads to a strong decrease of the temperatures in the atmosphere.”

The model also threw up another surprise in that the volcanic resurfacing takes place at different locations at different times, with a handful of active volcanoes remaining after the atmosphere has cooled enough to immobilize the crust.

Unusual surface hot spots have recently been detected by ESA's Venus Express mission, but as yet, no active volcanoes have been identified. The hunt continues.

This special publication features the photography of British astro-imager Nik Szymanek and covers a range of photographic methods from basic to advanced. Beautiful pictures of the night sky can be obtained with a simple camera and tripod before tackling more difficult projects, such as guided astrophotography through the telescope and CCD imaging.
 U.K. STORE
 E.U. STORE
 U.S. & WORLDWIDE STORE

Hubble Reborn
Hubble Reborn takes the reader on a journey through the Universe with spectacular full-colour pictures of galaxies, nebulae, planets and stars as seen through Hubble's eyes, along the way telling the dramatic story of the space telescope, including interviews with key scientists and astronauts.
 U.K. STORE
 E.U. STORE
 U.S. & WORLDWIDE STORE

The Planets
From tiny Mercury to distant Neptune and Pluto, The Planets profiles each of the Solar System's members in depth, featuring the latest imagery from space missions. The tallest mountains, the deepest canyons, the strongest winds, raging atmospheric storms, terrain studded with craters and vast worlds of ice are just some of the sights you'll see on this 100-page tour of the planets.
 U.K. STORE
 E.U. STORE
 U.S. & WORLDWIDE STORE

3D Universe
Witness the most awesome sights of the Universe as they were meant to be seen in this 100-page extravaganza of planets, galaxies and star-scapes, all in 3D!
 U.K. STORE
 E.U. STORE
 U.S. & WORLDWIDE STORE

This new poster features some of the best pictures from NASA's amazing Mars Exploration Rovers Spirit and Opportunity.
 U.K. STORE
 E.U. STORE
 U.S. & WORLDWIDE STORE