New Study Reveals How Venus Lost Its Water
Venus, the scorching hot second planet from the Sun, has long fascinated scientists due to its similarities to Earth’s size, mass, density, and geological composition. One particularly intriguing question has been whether Venus once had vast oceans around 3 billion years ago. A new study from the University of Colorado Boulder aims to shed light on this mystery by investigating the disappearance of Venus’ water.
In order to tackle this question, researchers turned to computer modeling, a common tool in modern astronomy. By inputting known parameters, scientists can simulate processes that occur in distant worlds. However, an important obstacle in the theory of a “watery Venus” is the lack of oxygen atoms in its atmosphere. If Venus did have oceans in the past, they would have evaporated under the influence of the sun’s rays, saturating the atmosphere with hydrogen and oxygen atoms. While hydrogen could escape into space through a process called “dissociative recombination,” it is unclear what happened to the oxygen.
To address this issue, Alexander Warren and Edwin Kite from the University of Chicago created a computer model of Venus’ atmosphere. Running the model 94,080 times, they found that only in a small percentage of cases (0.4%) did the data closely match today’s indicators. The results suggested that oxygen may have disappeared from the atmosphere by either getting trapped in oxidizing volcanic rocks (basalt) or gradually seeping into space over billions of years.
However, a new computer model developed by Erin Kangi and Michael Chaffin of the Laboratory for Atmospheric and Space Physics (LASP) proposes a different culprit for the loss of water on Venus. This model focuses on the chemical processes and reactions occurring on the planet. According to their findings, the HCO+ molecule, present in the upper layers of Venus’ atmosphere, may be responsible for the active loss of water.
HCO+ is an ion composed of one atom of hydrogen, carbon, and oxygen. When a “greenhouse crisis” occurred on Venus billions of years ago, causing surface temperatures to soar and all liquid oceans to evaporate, HCO+ could have played a role in the subsequent disappearance of water. Constantly produced in the atmosphere, HCO+ reacts with free electrons. This recombination splits the HCO+ ions, allowing hydrogen atoms to escape into space. As a result, Venus’ atmosphere becomes depleted of one of the two key atoms involved in the formation of water.
While the hypothesis involving the HCO+ ion seems convincing, there is one major dilemma—the predominance of this ion has never been detected in Venus’ atmosphere. The authors of the study suggest that this gap in knowledge may be due to inadequate scanning techniques. Most planetary missions in recent decades have focused on Mars, overlooking the potential explanations for water loss on Venus.
In the coming years, several planetary missions will be launched to Venus, including NASA’s Deep Atmosphere Venus Investigation of Noble Gases, Chemistry, and Imaging (DAVINCI) set to launch in 2029. Though DAVINCI will not have a scanner to determine the saturation of HCO+ ions, scientists at the University of Colorado Boulder hope that the data obtained from this mission will be sufficient to confirm or refute their hypothesis.
The mystery surrounding Venus’ lost water continues to captivate scientists and space enthusiasts alike. As technology advances and more missions are dedicated to exploring this intriguing planet, we inch closer to unraveling its secrets. The answers may lie hidden within the depths of Venus’ atmosphere, waiting to be discovered by future space explorers.
