They say a chemical reaction called HCO+ dissociative recombination – a process that would double the loss of water into space as the standard steamy escape methods – could be to blame for Venus’ dryer nature.

That’s despite being a close neighbour and being similar in size and source material to Earth with research suggesting that water from Venus’s once steam-dominant atmosphere was lost to space via a mechanism called hydrodynamic outflow. However, this mechanism cannot remove all the water needed to explain current conditions, and other studied escape mechanisms are too slow to complete the process of water removal.

So the researchers propose HCO+ dissociative recombination, which produces more escaping hydrogen than previously suggested processes.

The reaction would nearly double the rate of water loss to space from Venus and would resolve longstanding difficulties in explaining measured water abundances and isotope ratios on Venus. Future Venus spacecraft missions need to measure HCO+ abundances to determine if the reaction is indeed the dominant mechanism for water loss.