By Richard Ernst, Carlton University
We can know a lot about climate change from our sister planet Venus. Currently Venus’s surface temperature is 840 ° F (450 ° C) – the temperature of an oven’s self-cleaning cycle – and an atmosphere dominated by carbon dioxide (96%) with a density of 90 times that of Earth.
Venus is a very strange place, completely uninhabited, probably about 40 miles (60 km) above except in clouds where recent phosphine discoveries may suggest ongoing microbial life. But the surface is completely inhumane.
However, Venus once had an earth-like climate. According to recent climate modeling, the surface of Venus has had temperatures similar to the current Earth for most of its history. It was also likely sea, rain, perhaps ice, perhaps continent and plate tectonics, and more speculative, perhaps even surface life.
Less than a billion years ago, a fugitive greenhouse effect dramatically changed the climate. It can be surmised that the volcanic intense period caused by this great climate change event pumped enough carbon dioxide into the atmosphere, causing the oceans to evaporate and the water cycle to end.
Evidence of change
This hypothesis from the climate model prompted a master’s student in my group, Sarah Khwaja (co-supervised with geologist Claire Samson) to testify in the Venusian rocks for this proposed climate change event.
Since the early 1990s, my Cartlan University research team – and more recently my Siberian team at Tomsk State University – has been mapping and interpreting the geological and tectonic history of Earth’s remarkable sister planet.
The Soviet Venera and Vega missions of the 1970s and 1980s landed on Venus and took photographs and evaluated the structure of the rocks before the landers failed due to high temperatures and pressures. However, our most comprehensive view of Venus’s surface has been provided by NASA’s Magellan spacecraft in the early 1990s, which used radar to look through the dense cloud layer and cover 98% of Venus’s surface Produces more detailed images.
A view of the surface of Venus created by radar on the Magellan spacecraft.
Our search for geological evidence of the great climate change event prompted us to focus on Venus on the oldest type of rocks, called tesserae, which are a complex form of a complex, long geological history. We thought that these oldest 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 climate change event.
Given poor resolution elevation data, we used an indirect technique to try to identify ancient river valleys. We demonstrated that small lava flows from the surrounding volcanic plains filled the valleys in the margins of Tesseri.
To our astonishment these Tesseri valley patterns were similar to the river flow patterns on Earth, leading to our suggestion that these Tesseri valleys were formed by river erosion over a period of time with Earth-like climatic conditions. My Venus research group at Carlton and Tomsk State Universities are studying tessera lava flows for any geological evidence of infection in extremely hot conditions.
To understand how a volcano on Venus can produce such a change in climate, we can look at the history of Earth for analogs. We can find analogy in the super-eruption, like the last eruption of Yellowstone, 630,000 years ago.
But such volcanoes are smaller than in large igneous provinces (LIPs) occurring in about 20–30 million years. These eruption events can release enough carbon dioxide on Earth, causing widespread climate change on Earth, including widespread extinction. To give you a sense of scale, consider that the smallest LIPs produce enough magma to cover the whole of Canada to a depth of about 30 feet (10 m). The largest known LIP produced enough magma that covered the size of Canada to a depth of about 5 mi (8 km).
LIP analogs on Venus include individual volcanoes that extend up to 300 mi (500 km), extensive lava channels that are up to 4,300 mi (7,000 km) long, and there are also interconnected crack systems – where the crust is breaking apart Is – up to 6,000 miles (10,000 km) long.
If a LIP-style volcano was the cause of a great climate change event on Venus, could a similar climate change occur on Earth? We can imagine a scenario of many millions of years in the future when many LIPs can occur randomly at the same time, causing such horrific climate changes on Earth that can presently cause conditions like Venus.
Richard Ernst, Scientist-in-Residence, Earth Sciences, Carlton University (a professor at Tomsk State University, Russia), Carlton University
This article is republished from chit chat Under a Creative Commons license. Read the original article.
Bottom Line: Venus has a surface temperature of 840 ° F (450 ° C) and a density of 90 times the atmosphere dominated by carbon dioxide. However, for most of its history, Venus likely had an Earth-like climate, with oceans, rain, perhaps ice, perhaps continents and plate tectonics, and even more speculative, perhaps surface life. Then, less than a billion years ago, Venus’ climate changed dramatically due to a fugitive greenhouse effect.