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Week 19/2011: Twins of space, poles apart

Venus and Earth are the twins of our solar system, rocky planets resembling each other with respect to their mass and size. They were also presumably formed in similar conditions but have very different atmospheres.

“Venus has a strong, thick and hot atmosphere, which consists primarily of carbon dioxide. A strong greenhouse effect prevails on Venus, while the Earth’s rich atmosphere contains nitrogen and oxygen and nurtures life,” says physicist Riku Järvinen.

The difference between atmospheres could be smaller considering that Venus orbits the Sun only thirty per cent closer than the Earth. The reasons behind the different developments are not yet fully understood. According to Järvinen, one explanation may be found in the intrinsic magnetism in the planets.

“The Earth has an intrinsic magnetic field resembling a bar magnet. This is missing from Venus. The magnetism has an effect on how the planets experience the solar wind. Thanks to the intrinsic magnetic field, solar wind is guided far past the Earth’s atmosphere, whereas in Venus’s case, the solar wind gets close to the planet and releases particles from its upper atmosphere in space.”

In his dissertation, Järvinen studies how the upper atmosphere particles are released and how they move in the proximity of the planet.

“We studied where the particles got the energy to escape. We found that they could accelerate because of the effect of the solar wind.”

In his research, Järvinen used a simulation model developed at the Finnish Meteorological Institute. The model is based on plasma physics, or equations of charged particles and gasses.
In particular, the three-dimensional computer model studied the ion escape caused by the solar wind observed by European Space Agency’s Venus Express spacecraft. The use of the model is computationally extremely challenging since the model follows the movements of individual ions and the modelled environment is approximately 40,000 kilometres each way and covers the all of the space near the planet and its particle environment.

Text: Tapio Ollikainen
Photo: ESA
Translation: AAC Global

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