Representation of an artist from the surface of Venus. Image via Shutterstock / The conversation.
By Richard Ernst, Carleton University
We can learn a lot about climate change from Venus, our sister planet. Venus currently has a surface temperature of 450 degrees C (840 degrees F), the temperature of the self-cleaning cycle of an oven, and an atmosphere dominated by carbon dioxide (96%) with a density 90 times higher than that of the earth.
Venus is a very strange place, totally uninhabitable, except perhaps in the clouds, about 60 km away, where the recent discovery of phosphine may suggest a floating microbial life. But the surface is totally inhospitable.
However, Venus probably had an Earth-like climate. According to recent climate models, for much of its history, Venus had similar surface temperatures to today’s Earth. It probably also had oceans, rain, maybe snow, maybe continents and plate tectonics, and even more speculatively, maybe even surface life.
Less than a billion years ago, the climate changed drastically due to a fugitive greenhouse effect. It can be speculated that an intense period of volcanism pumped enough carbon dioxide into the atmosphere to cause this great climate change event that evaporated the oceans and caused the end of the water cycle.
Change tests
This hypothesis of climate modelers inspired Sara Khawja, a master’s student in my group (co-directed with geoscientist Claire Samson), to look for evidence on Venusian rocks for this proposed climate change event.
Since the early 1990s, my research team at Carleton University and, more recently, my Siberian team at Tomsk State University, have been mapping and interpreting the geological and tectonic history of the remarkable sister planet of the Earth.
The Soviet Venera and Vega missions of the 1970s and 1980s landed on Venus and took photographs and evaluated the composition of the rocks, before the terrorists failed due to the high temperature and pressure. However, our most complete view of the surface of Venus has been provided by NASA’s Magellan spacecraft in the early 1990s, which used radar to see through the dense layer of clouds and produce detailed images of more than 98% of the surface of Venus.
A visualization of the surface of Venus produced by radar aboard the Magellan spacecraft.
Ancient rocks
Our search for geological evidence of the great event of climate change led us to focus on the oldest type of Venus rocks, called tessellations, which have a complex appearance that suggests a long and complicated geological history. We thought that these older rocks had the best chance of preserving evidence of water erosion, which is such an important process on Earth and should have occurred on Venus before the great event of climate change.
Given the poor resolution altitude data, we used an indirect technique to try to recognize ancient river valleys. We showed that the younger lava flows from the surrounding volcanic plains had filled valleys at the edges of the tiles.
To our surprise, these patterns of the tile valleys were very similar to the flow patterns of the rivers on Earth, which led to our suggestion that these tile valleys were formed by the erosion of rivers for a time with Earth-like climatic conditions. My Venus research groups at Carleton and Tomsk state universities study post-tesserae lava flows for any geological evidence of the transition to extremely hot conditions.
A portion of Alpha Regio, a topographic mountainous area on the surface of Venus, was the first feature of Venus to be identified from Earth-based radar. Image via NASA-JPL.
Terrestrial analogies
To understand how Venus’ volcanism could produce such climate change, we can look for analogues in Earth’s history. We can find analogies in super-eruptions like the last Yellowstone eruption that occurred 630,000 years ago.
But this volcanism is small compared to the large igneous provinces (LIPs) that occur approximately every 20-30 million years. These eruption events can release enough carbon dioxide to cause catastrophic climate change on Earth, including mass extinctions. To give you a sense of scale, keep in mind that smaller LIPs produce enough magma to cover all of Canada to a depth of about 30 feet (10 meters). The largest known LIP produced enough magma that would have covered an area the size of Canada to a depth of almost 8 miles (8 km).
LIP analogs on Venus include individual volcanoes up to 500 km in diameter, extensive lava channels up to 7,000 km long, and there are also associated rift systems, where the crust is separating. up to 10,000 km long.
If LIP-style volcanism was the cause of the great event of climate change on Venus, then could Earth-like climate change occur? We can imagine a scenario of many millions of years in the future when multiple LIPs that occur randomly at the same time could cause the Earth to have climate change so fleeting that it leads to conditions like the current Venus.
Richard Ernst, resident scientist, earth sciences, Carleton University (also a professor at Tomsk State University, Russia), Carleton University
This article is republished from The conversation under a Creative Commons license. Read the original article.
Summary: Venus has a surface temperature of 840 degrees F (450 degrees C) and an atmosphere dominated by carbon dioxide, with a density 90 times higher than that of Earth. However, for much of its history, Venus probably had an Earth-like climate, with oceans, rain, perhaps snow, perhaps continents, and plate tectonics, and even more speculatively, perhaps even surface life. Then, less than a billion years ago, Venus ’climate changed drastically due to a fleeting greenhouse effect.
