Moa Persson, of the Swedish Institute of Space Physics (IRF) and Umeå University, is defending her doctoral thesis on the subject of just how much water has escaped from Venus’ once-temperate surface out into space, and she has found that the amount is not that much, relatively speaking.
Persson analyzed data collected by IRF’s instrument on Venus Express, ASPERA-4, to determine how many ions were collecting around Venus. These ions turned out to be, on average, one oxygen atom for every two protons, which indicates water. Ionized hydrogen, of course, is one proton. Persson then noted that the level of ion escape varied with the solar cycle, and if something does a thing now, it likely has done a thing in the past.
When the sun is quieter, during solar minimum, more protons escape the atmosphere. During solar maximum, the solar winds are stronger, and the protons end up back in the atmosphere more than they escape. As Persson stated: The surface of Venus today is comparable to hell. It is extremely dry and has a temperature of 460 degrees but historically the surface was more hospitable with a wealth of water that could reach a depth of several hundreds of meters if spread equally over the surface. This water has disappeared from Venus. My thesis shows that only a few decimetres of this water has escaped to space.
Note: A decimeter is one-tenth of a meter.
This research has implications for other planets like Earth and even Mars, which once held liquid water itself, and can be used for comparison to similar studies.