The Earth's nearest planetary neighbour might still be geologically active according to a new study.
Venus is sometimes called Earth's sister planet because they're almost the same size and composition. But it's a twisted sister; temperatures hot enough to melt lead, sulphuric acid rain, and a crushing atmospheric pressure one hundred times that of Earth.
Now a team of scientists led by Dr Suzanne Smrekar from NASA's Jet Propulsion Laboratory in California have found new evidence for recently active volcanoes on Venus.
Their report, which appears today in the journal Science identifies hotspots on Venus that indicate young rocks with abnormally high level of heat compared to their surroundings.
"It shows the rocks haven't degraded despite exposure to the harsh Venusian weather," says Smrekar. "It means the hotspots are recently active volcanoes, with lava flows younger than 2.5 million years."
Similar to Hawaii
Smrekar and colleagues used surface heat data gathered by sensors aboard the European Space Agency's Venus Express spacecraft.
Data collected by NASA's Magellan spacecraft in the 1990s identified nine hot spots similar to those found on the islands of Hawaii. Broad topographic rises and gravity anomalies found at these hot spots suggest there could be active mantle plumes close to the surface.
Using the Visible and Infrared Thermal Imaging Spectrometer aboard Venus Express, Smrekar's team examined three of these hotspots.
"They're places geologically like Hawaii, and so are the most likely sites for volcanic activity. They could be active now but there's no evidence that they're currently erupting," says Smrekar.
"The clue was finding basalt rock that hasn't been weathered or chemically changed. Even on Earth when lava erupts on the surface, it interacts with the atmosphere and changes composition at the crust.
"On Venus, because it's so hot with a dense carbon dioxide and sulphur dioxide atmosphere, we expect lava to quickly react when it hits the surface undergoing chemical and mineral changes."
But Smrekar says that process hasn't yet happened at these hotspots.
"We believe that means these are relatively fresh."
Because of the small number of impact craters on Venus, scientists know the planet's surface isn't much more than half a billion years old.
Smrekar says that's a relatively young surface, like the Earth's, and much younger than Mars. But unlike Earth, there's no evidence of plate tectonic activity on Venus or Mars.
"It means Venus is a lot like Earth, but not exactly the same. It's kind of a laboratory for understanding how the Earth works," she says.
"As we find more planets around other stars, maybe we'll find out what's more typical, Earth or Venus."
According to Smrekar, a new mission to visit the surface of Venus is currently being considered for funding.
Called Surface and Atmospheric Geochemical Explorer (SAGE), the lander will tough to survive the journey to the surface.
During the 1970s, a number of Soviet spacecraft landed on the Venusian surface, but lasted no mor ethan a hour before being cooked and crushed in the hostile environment.
Smrekar says SAGE could answer a number of questions relating to Venus and help scientists better understand data from orbiting spacecraft such as Venus Express.