How Long was Venus Potentially Habitable and What Caused it to Become the Volcanic and Acidic Planet it is Today?

Venusian Habitable Climate Scenarios: Modeling Venus Through Time and Applications to Slowly Rotating Venus‐Like Exoplanets

by: M.J. Way, Anthony D. Del Genio 

Summarized by: Lisette Melendez

What data were used? Nowadays, Venus is known for its extreme climate. It’s the hottest planet in our Solar System (with a surface temperature of about 840°F!), and the only planet that spins in the opposite direction. In fact, Venus spins so fast that its acidic clouds can travel completely around the planet in 5 days. Despite its extremities, Venus is also known as Earth’s sister planet. Both planets formed very close to one another and their shape and mass are very similar. So how did their surfaces become so distinct from one another? There are many hypotheses posed as to what early Venus looked like, ranging from a stable world with surface liquid water, to a volcanic world with a magma ocean and a carbon dioxide atmosphere. In order to better understand the early history of Venus, scientists used the data that we have about early Earth and simulations generated by various satellites orbiting Venus.

Methods: By modeling early Venus to closely match the conditions of early Earth using NASA’s ROCKE-3D (a tool you can try out yourself!) general circulation models, the scientists were able to examine how changes in factors like surface water and rotation rate affected Venus’s climate.

Results: The team discovered that Venus’s climate may have been stable and temperate with liquid water at its surface for most of the planet’s history, as shown in Figure 2. So, what caused the huge change? The authors argue that it was caused by the synchronized eruption of massive volcanoes, leading to the large igneous provinces (LIPs, or large collection of volcanic rocks) seen on Venus today. These LIPs could have triggered a runaway greenhouse effect on Venus, a situation where a planet absorbs more energy from the sun than it can radiate back into space. This leads to an inability to cool down and to the evaporation of surface water on the planet. On Earth, some LIPs are known to coincide with mass extinctions, so these events are already known to create colossal changes on the surface of a planet.

Figure 1: An image of the harsh surface of Venus, the most volcanic planet in our Solar System. Credit: NASA JPL.

Why is this study important? This study is important because it gives us insight as to whether early Venus ever had life-friendly environments: did the planet ever experience the same evolutionary processes that Earth did? It also helps us understand exoplanets, which are planets outside of our Solar System, which are tens of thousands of years away by rocket travel. Some of these rocky exoplanets orbit very close to their host stars, much like Venus orbits close to the Sun. So, perhaps these exoplanets host surface liquid water as well!

Figure 2: A graphical representation of the possible climate history of Venus. For most of its history, it is proposed that Venus had a temperate climate with surface water.

The big picture: After analyzing the various models of Venusian history, scientists found that Venus was potentially habitable, like Earth is, for most of its lifetime, which is remarkably different from the acidic, scorching atmosphere we observe today. Large, simultaneous volcanic eruptions may have made it impossible for Venus to cool down, and the resultant dry and hot atmosphere could have led Venus to its current conditions. Even so, more observations from Venus’s surface are needed to fully understand its history and transformation.

Citation: Way, M. J. & Genio, A. D. D. Venusian Habitable Climate Scenarios: Modeling Venus Through Time and Applications to Slowly Rotating Venus-Like Exoplanets. Journal of Geophysical Research: Planets 125, e2019JE006276 (2020).

 

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