Using two ESA spacecraft, planetary scientists are watching the atmospheres of Mars and Venus being stripped away into space.
The simultaneous observations by Mars Express and Venus Express give scientists the data they need to investigate the evolution of the two planets’ atmospheres.
Scientists call this work comparative planetology. Mars Express and Venus Express are so good at it because they carry very similar science instruments. In the case of the Analyser of Space Plasmas and Energetic Atoms (ASPERA), they are virtually identical. This allows scientists to make direct comparisons between the two planets.
The new results probe directly into the magnetic regions behind the planets, which are the predominant channels through which electrically-charged particles escape. They also present the first detection of whole atoms escaping from the atmosphere of Venus, and show that the rate of escape rose by ten times on Mars when a solar storm struck in December 2006.
By observing the current rates of loss of the two atmospheres, planetary scientists hope that they will be able to turn back the clock and understand what they were like in the past. “These results give us the potential to measure the evolution of planetary climates,” says David Brain, Supporting Investigator for plasma physics for Venus Express and Co-Investigator for ASPERA on Mars and Venus Express at the University of California, Berkeley.