Scientist with the European Space Agency (ESA) and NASA say that Venus is still geologically active. The Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) aboard the ESA's Venus Express spacecraft has identified relatively young lava flows that suggests the planet remains capable of volcanic eruptions.

ESA researchers were able to determine the relative age of the flows based on how they react  with Venus' atmosphere. On Earth, lava flows react rapidly with oxygen and other elements in the atmosphere, changing their composition. On Venus, the process should be similar, though more intense because of the hotter, denser atmosphere, chiefly of carbon dioxide.
 
The fact that the lava flows appear to have different compositions from their surroundings suggest a lack of surface weathering, indicating that the flows erupted relatively recently. Scientists estimate that the flows are possibly as geologically recent as 2.5 million years ago – and likely much less, possibly even currently active.
 


 This figure shows the volcanic peak Idunn Mons (at 46°S, 214.5°E) in the Imdr Regio area of Venus. The topography derives from data obtained by NASA's Magellan spacecraft, with a vertical exaggeration of 30 times. Radar data (in brown) from Magellan has been draped on top of the topographic data. Bright areas are rough or have steep slopes. Dark areas are smooth.

The colored overlay shows the heat patterns derived from surface brightness data collected by the visible and infrared thermal imaging spectrometer (VIRTIS) aboard ESA's Venus Express spacecraft. The brightness signals the composition of the minerals that have been changed due to lava flow. Red-orange is the warmest area and purple is the coolest. The warmest area is situated on the summit, which stands about 2.5 km above the plains, and on the bright flows that originate there. Idunn Mons has a diameter of about 200 km.

(Photo Credit: ESA/NASA/JPL)

It has long been recognized that there are simply not enough craters on Venus. Something is wiping the planet’s surface clean. That something is thought to be volcanic activity but the question was whether it happens quickly or slowly. These new findings provide strong evidence that a gradual sequence of smaller volcanic eruptions is likely responsible.

VIRTIS records the brightness of surface rocks, providing an estimate of ‘emissivity’. In 2008, scientists published a map of the variation of infrared emissivity across the southern hemisphere of Venus. They targeted three regions that geologically resemble Hawaii, well known for its active volcanism, and showed that the regions on Venus have higher emissivities than their surroundings, indicating different compositions.

“There are some intriguing models of how Venus could have completely covered itself in kilometers of volcanic lava in a short time, but they require that the interior of Venus behaves very differently from Earth. If volcanism is more gradual, this implies that the interior may behave more like Earth, though without plate tectonics,” says  Sue Smrekar, a scientist at NASA's Jet Propulsion Laboratory in California