The colored overlay shows the emitted thermal radiation of a volcanic crater, as recorded by the VIRTIS spectrometer on the space probe Venus Express. Red and yellow means high heat radiation. Image: NASA, JPL, ESA
Read aloud The volcanoes on Venus have recently come to rest according to geological understanding of time. An international team of researchers found this out by analyzing thermal images taken from the Venus Express spacecraft. Thus, lava rock from three point melting regions on Venus showed an exceptionally high heat output. The deposits of these hotspots may have originated less than 250, 000 years ago: the high temperatures that prevail on Venus, the stone weathers namely relatively fast and it form minerals that have low heat radiation. The study also shows that Venus was and is a geologically active planet. Earth and Venus have comparable size and heat production at their core. Nevertheless, the tectonic processes on their surfaces are very different: on Earth there are pronounced plate tectonic processes, while on Venus the near-surface rock layer is rather rigid. Nevertheless, individual volcano craters and hotspots can be found on Venus as signs of a temporary strong geological activity. Hotspots are areas where magma rises close to the surface and sometimes breaks through the earth's crust, creating a volcano.

Scientists working with Suzanne Smrekar of the Jet Propulsion Laboratory in Pasadena looked more closely at three such centers of volcanic activity. To do this, they used thermal images taken by the VIRTIS spectrometer on the Venus Express spacecraft of the European space agency European Space Agency. VIRTIS, the abbreviation stands for Visible and Infrared Thermal Imaging Spectrometer, captures the emitted heat radiation of objects like a thermal imager. The analysis of the images showed that solidified lava flows on the sides of volcanic elevations emitted significant amounts of heat compared to the surrounding area. The reason for this was not an ongoing cooling off since the last eruption: The deposited volcanic rocks had been deposited relatively recently and not yet weathered heavily. Under the special conditions on Venus with temperatures around 460 degrees and a pressure of 90 bar, iron-containing silicates, such as pyrite, weather to hematite, quartz and other minerals. These emit significantly less heat than the starting rocks under the same conditions.

In laboratory experiments, the researchers simulated the weathering of volcanic rocks in a venus-like atmosphere. From the results they were able to estimate a maximum age of the lava flows of 2.5 million years. But more likely is an age of around 250, 000 years. In geological periods, the volcanoes have been active only recently.

Suzanne Smrekar (Jet Propulsion Laboratory, Pasadena) et al .: Science, doi: 10.1126 / science.1186785 ddp / science.de? Thomas Neuenschwander advertisement

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