The 2004 Venus in situ exploration mission aimed to collect information about the extreme atmospheric conditions that render the planet very different from Earth.
The difference in the escape velocities of ions may help to explain why Venus isn’t more like Earth, scientists say, and it may come down to a planet’s core.
Oxygen and hydrogen ions in Venus’s atmosphere do not behave the same when exposed to the solar wind, according to scientists at the Finnish Meteorological Institute in Helsinki.
“An oxygen ion is 16 times more massive than a hydrogen ion,” said lead author, Riku Jarvinen. “We found that the mass difference between the two ion species makes them move very differently from each other in the electric and magnetic fields created by the solar wind around Venus.”
Ions ‘blown’ to higher velocities
In the upper atmospheres of planets, particles are ionised by the sunlight, which is how planetary ionospheres are created, said Jarvinen of the study published in Geophysical Research Letters.
In Venus’s case, the uppermost planetary ions are in contact with the solar wind flowing close to the planet. When this occurs, the ions get energy from the solar wind and are accelerated, as though ‘blown,’ to velocities higher than the escape velocity of the planet and are lost from the atmosphere.
Magnetic fields generated in the planet’s core determine the ways in which its atmosphere reacts to the solar wind, said Jarvinen.
Read more here Escaping ions explain the mystery of Venus | COSMOS magazine.