Venus is not a “spoiled Earth”: it never had oceans or the conditions for life to originate

Many scientists consider Venus to be a “deteriorated” Earth. On Venus, conditions developed for a powerful greenhouse effect that could have destroyed ancient life on it. But what if Venus was always dry? Scientists from the University of Cambridge decided to test this possibility, which would provide a clue to the search for life on exoplanets. As modeling has shown, conditions could have developed on Venus without the formation of oceans and a cradle for life.

Two scenarios for the evolution of Venus: the most likely dry (upper) and wet (lower). Image source: Nature Astronomy 2024

On the surface of Venus, the atmospheric pressure is 92 times higher than on Earth at sea level, and the temperature reaches 465 °C. These conditions were formed over billions of years, although the starting conditions of Venus, Mars and Earth were the same. Studying the mechanisms of climate change on these three solar system planets could help determine which exoplanets should be looked for for signs of life beyond our star system. This is also important for predicting the earth’s climate, taking into account possible development scenarios.

Scientists have data on the composition of Venus’s atmosphere, including the percentage of water, carbon dioxide and carbonyl sulfide. The model makes it possible to calculate the rate of decay of these compounds in the atmosphere under the influence of solar radiation, as well as to determine the sources of their replenishment.

«By calculating the current rate of destruction of water, carbon dioxide and carbonyl sulfide in the atmosphere, which must be replenished by volcanism to maintain its stability, we showed that the interior of Venus is dry, writes the team led by Cambridge astronomer Tereza Constantinou. “The dryness inside the planet indicates that Venus completed its era of drying out the magma ocean and after that had a dry surface for a long time. Thus, volcanic replenishment of the atmosphere indicates that the planet was never suitable for life in liquid water.”

On Earth, volcanic emissions are dominated by water vapor, which indicates significant reserves of water hidden in the bowels of the planet for billions of years. The Earth’s moist internal structure allowed for the emergence of oceans and life. On Venus, modeling has shown that the level of water vapor in volcanic emissions is only about 6%. The mantle rocks of Venus are extremely dry. Under such conditions, even in ancient times, oceans could not form on Venus, which means that there were no natural cradles for the emergence of biological life similar to that on Earth.

The conditions prevailing on Venus transformed the water reserves into a vapor state. Under the influence of sunlight, water disintegrated into its constituent atoms, and hydrogen, as the lightest element, quickly left the atmosphere. It is noteworthy that the atmosphere of Venus at a certain altitude can be suitable for microbial life.

In the coming years, from three to five interplanetary stations will be sent to Venus. Some of them will search for life in the clouds of the planet, since its surface is solid dry land.