On Venus, the planet that is a twin of Earth, there is almost no water. Until now, the reason for this has only been partially understood. However, planetary scientists are now presenting an explanation that comes down to just one ion!
Venus is the second planet closest to our Sun. It is often referred to as Earth’s twin because the two planets have very similar sizes and masses. However, they are actually very different from each other. Among all the things that set them apart, one key difference is the lack of water on Venus. Scientists have long been searching for an explanation, and now, planetary scientists from the University of Colorado at Boulder (USA) seem to have found one. They detail their findings in the journal Nature.
It is important to note that there is about 100,000 times less water on Venus than on Earth. To put this into perspective, researchers explain that if all the water on Earth were spread over the entire surface of our planet, the liquid layer would be about three kilometers deep. The same calculation on Venus would result in a water depth of only… three centimeters!
An Ion Responsible for the Absence of Water on Venus
How is this possible? Even though scientists believe that billions of years ago, at the time of their formation, Venus and Earth must have received the same amount of water. Initially, because at some point, clouds of carbon dioxide (CO2) in Venus’ atmosphere triggered a powerful greenhouse effect. Temperatures rose to an average of 470°C, causing all the water to evaporate, with most of it drifting into space.
However, according to astronomers, Venus appears even drier than it should be under these circumstances. “It’s like a bottle of water being emptied. There are always a few droplets left inside. But not on Venus,” the researchers describe. And the culprit could very well be an ion with the chemical formula HCO+. The formylion cation, composed of an atom of…Water is made up of two atoms of hydrogen, one atom of carbon, and one atom of oxygen. Planetary scientists explain that in high planetary atmospheres, water mixes with CO2 to form this particular ion. The idea is that it does not survive long in Venus’ atmosphere. When electrons encounter HCO+ ions, a recombination takes place – chemists refer to it as dissociative recombination – and the ions split into two, releasing hydrogen atoms (H) that drift away into space. Without hydrogen, it’s impossible to reform water (H2O).
Researchers from the University of Colorado have calculated that Venus should have significant volumes of HCO+. It should even be the most abundant ion in its atmosphere. However, scientists have never observed this ion around Venus. They attribute this to not having the right instruments pointed at Venus yet. Even NASA’s DaVinci mission won’t be able to detect HCO+ in Venus’ atmosphere. Now that scientists know what to look for, future missions to the second planet in our solar system might include a dedicated instrument. Water is crucial for life, so understanding the conditions that support the presence of liquid water in the Universe is essential for our search for extraterrestrial life.