By Letter to the Editor on March 23, 2020.
There’s transcendence to “Venus: The Evening Beacon” (Feb. 29) and the dates for this planet’s successive conjunctions. Unfortunately, there are also statements outdated or wrong, e.g., Venus’ clouds “comprised of CO2” when they’re really sulfur dioxide. Worse is the Zombie from 50 years ago, still blamed for Venus’ ferocious heat: “The clouds also produce the greenhouse effect, trapping the solar energy.” Updating the science undercuts the panic in our perception of CO2. Venus is actually not the model they say it is.
When the Messenger probe began mapping Mercury in 2011, its ceramic heat shield registered 370¡C from the sun. Venus, 52 million kilometres more distant, radiated an ongoing 467¡C – 15 per cent more heat than it receives. Its surface pressure is 100 times Earth’s because its CO2 (96.4 per cent of its atmosphere) is not a gas but a supercritical fluid, dense enough to withstand solar winds despite Venus’ lack of magnetic fields.
The heat and CO2 led to the early theory that Venus had suffered a runaway greenhouse effect. This in turn shocked our perceptions of terrestrial CO2 (0.039 per cent), then climbing in response to a modest warming (since levelled off). But a political grift was born.
The radar-mapping Magellan probe revealed that Venus is tectonically locked. Its surface crust spread out from the equator until it piled upward, in places like Maxwell Montes and Ishtar Terra, instead of subducting. On Earth, plate tectonics allow our world to shed excess heat; Venus uniformly exudes heat across its entire surface. On Earth, some 1,850 volcanoes occur along fault lines. Venus has an estimated 100,000 volcanoes scattered across its crust (the 2008-09 Venus Express read 500¡C temperature spikes, a cluster of them at Ganis Chasma, indicating active eruptions). A complete lack of surface water keeps its other features rigid.
The greenhouse effect cannot account for a core too molten to generate magnetic fields – but planetary geology can and does. It is in every way a different world. Venus is not analogous to the trace biogas conditions of Earth, and can’t be credibly used as an example of what might go wrong here.