Venus has lava tubes, and they are weird

We now know with certainty that massive underground tunnels, sculpted by lava, exist on Venus – and they are surprisingly wide and different from those of any other planet.

It is not controversial that the lava tubes – underground tunnels sculpted by La Roche Fondue – exist on earth, the Moon and Mars. Smaller with low gravity planets tend to form more cavernous tubes, in part because the rock walls are less likely to collapse with lower gravity. On the moon, for example, the tubes are so large that scientists have offered to use them as living shelters for astronauts, providing the armor of severe solar wind.

Scientists had seen clues of these lava tubes on Venus, from holes and pits which seem to have been formed on its surface, but it was not clear if these were caused by lava tubes below or by other geological processes, as from an active flaw line.

Now, Barbara de Toffoli at the University of Padova in Italy and her colleagues have found direct evidence of lava tubes in Venus. They also seem surprisingly wide and a volume comparable to those of the Moon, despite that Venus looks more like the earth in terms of mass and gravity.

“The terrestrial lava tubes have smaller volumes, the tubes of Mars have slightly larger volumes, then the tubes of the Moon have even larger volumes – then there is Venus, completely disturbing this trend, displaying volumes of very large tubes,” said Deo Toffoli at the Europlanet Sciences Congress in Helsinki, earlier this month. “It already gives the fact that there is probably something more about Venus playing an important role.”

Using radar and cartographic data of past missions, from Toffoli and his team analyzed how these pits were aligned and were arranged near large volcanoes. They found four clear examples which had no alternative geological explanation, such as tectonic activity. The pits also lined up with the steepest part of the slopes of the volcanoes, which is the direction that the lava would have traveled, and the ratio of their depth and their width was consistent with other known lava tubes.

The unexpected size of the tubes, in particular their width, suggests that the extreme Venusian environment, which is very hot and high pressure, could affect the way in which the melted rock moves under its surface, said Toffoli, and does not only depend on gravity as lava tubes on other planets. “Due to the very high pressure, there is a global flattening outside the tubes, instead of having a very intense erosion on the ground which generally occurs on other planets.”