How Climate changed to make Venus impossible to inhabit

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We can learn a great deal about climate change from Venus, our sister planet. Venus currently has a surface temperature of 450℃ — comparable to an oven’s self-cleaning cycle — and an atmosphere dominated by carbon dioxide (96%) with a density 90 times that of Earth’s.

Venus is an extreme environment, completely uninhabitable at the surface. The only possible exception lies in the clouds roughly 60 km above, where the detection of phosphine has sparked debate about potential microbial life. Yet the surface remains utterly hostile.

From Earth-like Past to Runaway Greenhouse

Venus once possessed an Earth-like climate. Climate models indicate that for much of its history the planet maintained surface temperatures similar to those on present-day Earth, with rainfall, oceans, and possibly even continents and plate tectonics.

Approximately one billion years ago the climate underwent a dramatic shift triggered by a runaway greenhouse effect. Intense volcanic activity is thought to have released enough carbon dioxide to initiate this transformation, evaporating the oceans and ending the hydrological cycle.

Evidence of Change

This hypothesis prompted Sara Khawja, a master’s student in our team (co-supervised by geoscientist Claire Samson), to search for geological evidence of the proposed climate shift in Venusian rocks.

Since the early 1990s, the Carleton University research group — and more recently our team at Tomsk State University — has been mapping the geological and tectonic history of Earth’s striking twin planet.

The Soviet Venera and Vega landers of the 1970s and 1980s touched down on Venus, capturing images and analyzing surface composition before succumbing to the extreme heat and pressure. Our most comprehensive view of the surface, however, comes from NASA’s Magellan mission in the early 1990s, which used radar to penetrate the thick clouds and map more than 98 percent of Venus.

Ancient Rocks and River Valleys

Our search for geological traces of the climate transition focused on tesserae — the oldest terrain on Venus, characterized by complex deformation that suggests a long and intricate geological past.

These ancient rocks offered the best prospect of preserving signs of water erosion, a process that must have been widespread on Venus before the runaway greenhouse took hold.

Using indirect methods due to limited topographic data, we examined how later lava flows interacted with tesserae margins. The valley networks we mapped closely resemble terrestrial river systems, supporting the idea that they were carved by flowing water under Earth-like conditions.

Our teams at Carleton and Tomsk State universities continue to study post-tesserae lava flows for further evidence of the transition to extreme heat. Also read: Email Marketing

Earth Analogues: Large Igneous Provinces

To understand how volcanism could drive such rapid climate change on Venus, we look to Earth’s geological record.

Super-eruptions, such as Yellowstone’s last major event 630,000 years ago, provide one reference point, yet far larger episodes — known as large igneous provinces (LIPs) — occur roughly every 20–30 million years and release enough carbon dioxide to trigger major climatic disruptions and mass extinctions.

The smallest LIPs produced enough magma to cover Canada in a layer about ten metres thick; the largest would have buried the same area under nearly eight kilometres of lava.

Venus hosts comparable features: giant volcanoes up to 500 km across, extensive lava channels reaching 7,000 km in length, and rift systems extending 10,000 km.

If LIP-scale volcanism caused Venus’s climate catastrophe, could a similar sequence of events unfold on Earth? In the distant future, the simultaneous occurrence of several large igneous provinces could potentially push our planet toward runaway greenhouse conditions resembling those on Venus today.

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