Geological Testing of Global Warming Models on Venus

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Geological Testing of Global Warming Models on Venus On Earth, there is growing recognition that huge volcanic events (up to millions of km3) known as Large Igneous Provinces (LIPs) are major drivers of rapid climate change sometimes leading to mass extinctions (where up to 90% of life was obliterated). On Venus, a major pulse of LIP-style volcanism occurred ~700 million years ago and released a massive volume of carbon dioxide CO2. This caused extreme greenhouse warming to a current surface temperature of 450oC (twice as hot as your oven), and an atmosphere 90 times as dense as that of the Earth and composed of composed of 96% CO2. As a consequence, there is no liquid water on the surface of Venus and therefore no significant water erosion. However, it has recently been proposed that prior to this hyper-warming event Venus had conditions that were more Earth-like, even including the presence of oceans and rivers, and the potential for life. I propose that this dramatic climate change model for Venus can be evaluated through geological mapping (using Magellan spacecraft radar data) of two types of units: older units called tesserae which could represent rocks like those of the Canadian shield, and younger widespread basaltic lava flows (similar to Hawaii) that cover 90% of Venus. Tesserae would have been emplaced prior to global warming at a time when there could have been water erosion on Venus. Our hypothesis is also that the earliest basaltic lava flows on Venus were also emplaced during cooler (Earth-like) conditions, while the later basaltic flows would have been emplaced under the much hotter current conditions. Our team has recently discovered evidence for water erosion in tesserae, consistent with the modelling. This discovery indicates that tesserae could have a much longer geological history than previously believed, maybe even extending back 4 billion years, like the earliest rocks on Earth. I propose a campaign of systematic mapping of tesserae (of their erosional history, linear structures and superimposed lava ponds) to help unravel their protracted geological history. I also propose a systematic detailed mapping of the oldest volcanic plains in order to identify the transition in climate from Earth-like to inhospitable, by identifying units exhibiting erosion being cut by units exhibiting no erosion. My research will provide geological constraints on this runaway greenhouse climate change on Venus that will provide insights into the risks of modern global warming on Earth. My research will allow comparison of the volcanic history of Venus with that of Earth. Given an early Earth-like history for Venus, the obvious question is why Venus took a different path than Earth. One possible answer is that Venus experienced multiple pulse of volcanism that increased temperature beyond a tipping point. If so perhaps Venus offers a perspective into Earth's future. This research will train three MSc and two PhD students.