Mars and Venus: Earth's 'failed' sibling worlds

UK scientists are also working with ESA's Mars Express and Venus Express missions. In this case they are studying unmagnetised objects. We are exploring other planets to see what causes the similarities and differences between them and the Earth. For example, Venus and Mars have no life now as far as we know. They also have no significant magnetic field. Might these facts be linked?

Mars once had water on the surface, and it once had a magnetic field. But overall, the Red Planet today is defenceless against the onslaught of the solar wind, which can pull or ‘scavenge’ the atmosphere away; and there’s no shield against the radiation which cascades through the atmosphere. Mars only has a thin carbon dioxide atmosphere, barely one per cent as dense as Earth’s atmosphere.

Venus, on the other hand, has an incredibly dense atmosphere, exerting a surface pressure 90 times greater Earth’s. But 'scavenging' is going on there too, at least in the upper reaches of the Venusian sky. There may be a current source replenishing the atmosphere: possibly volcanism. Venus Express is searching for signs of this, using radar and other instruments to penetrate the thick clouds.

UK scientists and manufacturers have a strong involvement in Venus Express. A team from the University of Oxford was involved in the mission planning. The Mullard Space Science Laboratory and the Rutherford Appleton Laboratory both have roles in ASPERA, a plasma analyser which investigates the interaction of the solar wind and the Venusian atmosphere; and scientists from Imperial College, and the University of Sheffield worked on the magnetometer.