Those of us out and about on Spring evenings have been treated to a brilliant beacon of light above the western horizon. This is the planet Venus, our closest solar system neighbour.
Venus has been called Earth’s “evil twin”, in that it is almost identical in size, mass and density to our own planet yet the surface environment is as inhospitable to life as one can imagine: crushing pressures similar to those half a mile under the ocean and temperatures hot enough to melt lead. It is not a coincidence that Venus’ surface is regarded as the closest real-life analog to the western civilisation’s notion of Hell.
Venus is also a difficult planet to map because it is enveloped in multiple, unbroken layers of cloud rendering optical instrument all but useless. Instead, radar is used to penetrate the cloud layers. These radar images have shown that Venus is riddled with volcanic mountains, meaning the planet was – and may still be – geologically active, however so far it has been impossible to tell if volcanic activity is taking place right now or a million years ago.
This question has now been answered. New research published this month in the journal Science reports on the discovery of the first active volcano on Venus. The discovery was made by pouring over data collected 30 yr ago by the US Magellan probe. Magellan orbited Venus for several years mapping the surface underneath the clouds with radar. The maps created with the Magellan data are still considered the state-of-the-art in Venus surface studies to this day.
Scientists studying the surface of Venus looked at Magellan images covering the same regions of the surface but sobtained at different times. In one set of images taken eight months apart, a feature on the flanks of Maat Mons (Figure) previously suspected to be a volcanic vent doubled in size from 2 to 4 square km and also changed in shape from being oblong to kidney-shaped. The conclusion: this vent was actively discharging lava in the 8 months that elapsed between images.
The discovery makes Venus only the second planet in our solar system with active volcanism, the only other objects similarly endowed being Io, a moon of Jupiter and Triton, a moon of Neptune. Earth’s other planetary neighbour, the planet Mars, also sports volcanos on its surface like the giant Olympus Mons structure, however none of these volcanoes show signs of being currently active.
The discovery of active volcanism on Venus comes at an opportune time, as Venus will soon be invaded by a flotilla of probes from the US, Europe and possibly India as well as privately-funded missions. These spacecraft will carry the next generation of radar instruments to Venus, capable of making out much finer detail than Magellan did. Just like the star of Venus on the evening sky, the future looks bright for making sense of the mysterious planet next door.