Venus and Earth: Sharing a common geological past?
“One of the takeaways from this study is that both planets very likely had plate tectonics operating roughly at the same period of time,” Dr. Weller remarked. If this is indeed true, it implies that Venus could have been much more Earth-like in various aspects. Plate tectonics, with its geochemical reactions, could have trapped and concealed a significant amount of the carbon dioxide that makes Venus inhospitable today. This opens up the possibility that Venus, billions of years ago, might have been a place where life could have thrived.
“That’s a very likely scenario,” Dr. Weller stated. “It does suggest that certainly Venus would have been cooler, and then there would have been more liquid water.”
Analyzing nitrogen in Venus’ atmosphereTo explore this theory, the team of scientists, including researchers from Brown University and Purdue University, employed an unconventional method. Instead of seeking visible evidence of plate tectonics like fault lines, they turned to the atmosphere, focusing on nitrogen in particular.
When rocky planets like Earth and Venus form, nitrogen is initially locked within minerals. However, during volcanic eruptions, minerals melt, releasing nitrogen into the atmosphere. This nitrogen then remains in the air, serving as a “diagnostic tool” for understanding a planet’s tectonic history, as Dr. Weller described it.
Stagnant lid vs plate tectonics
The researchers employed computer simulations to investigate two tectonic models: the stagnant lid and plate tectonics. The stagnant lid scenario resembles the conditions on Mars and Earth’s moon, with a solid, unmoving outer crust, keeping most gases trapped beneath it. On the other hand, Earth’s plate tectonics model involves the movement of tectonic plates, releasing gases into the atmosphere.
The simulations indicated that if Venus had always possessed a stagnant lid crust, as it does today, there would be less nitrogen in its atmosphere than what we observe today, which is about 3.5 percent.
A compelling conclusion
The most compelling explanation that emerged from their research was a combination of the two models. Venus might have experienced an early phase of plate tectonics, releasing substantial amounts of carbon dioxide and nitrogen, followed by a transition to a stagnant lid scenario.
Still a mystery
Although these findings are intriguing, scientists not involved in the research have cautioned that they are suggestive but not conclusive. Cédric Gillmann, a planetary scientist at the Swiss Federal Institute of Technology, emphasised that model-based publications are highly dependent on what is included and omitted. Joseph O’Rourke, a professor of earth and space exploration at Arizona State University, suggested that Venus’s geological history might not neatly fit into either the Earth-like or Mars-like categories.
One alternative theory proposed is the “plutonic squishy lid model,” where magma intrudes the outer crust without breaking it into tectonic plates. This model could explain unique surface features on Venus, such as circular formations called coronae, pushed upward by hot material rising from the mantle.
Future venus missions
To further unravel the secrets of Venus’s geological past, upcoming spacecraft missions will play a pivotal role. NASA’s Davinci spacecraft, scheduled to launch in 2029, will provide precise measurements of gases in Venus’s atmosphere, shedding light on present-day volcanic activity. Another NASA mission, Veritas, will capture high-resolution images of Venus’s surface and make detailed gravity measurements to help identify potential plate boundaries.
The European Space Agency is also planning to launch a mission named EnVision, aiming to comprehend why the conditions on Earth and Venus diverged so dramatically.
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