Washington-Scientists have discovered how the atmosphere of Mars turned to stone. British researchers believe they have worked out how Mars lost its early carbon dioxide-rich atmosphere to become the cold and arid planet it is today. The research provides the first direct evidence from Mars of a process, called ‘carbonation’ which currently removes carbon dioxide from our own atmosphere, potentially combating climate change on Earth.

It is widely recognised that accumulation of carbon dioxide in the Earth’s atmosphere is contributing to global warming.

However, the loss of carbon dioxide from the atmosphere of Mars around 4,000 million years ago is likely to have caused the planet to cool. So understanding how carbon dioxide was removed from the Martian atmosphere could lead to new ways of reducing the accumulation of greenhouse gases in our own atmosphere.

It formed from molten rock around 1,300 million years ago, and was blasted from the surface of Mars by a massive impact 11 million years ago. Since its discovery in Indiana, USA, in 1931, Lafayette has been studied by scientists around the world. The new research focused on a carbon-rich mineral called siderite. Although found in Lafayette previously, the team discovered that the siderite had formed by the process of ‘carbonation’, whereby water and carbon dioxide from the Martian atmosphere reacted with rocks containing the mineral olivine.

These reactions then formed siderite crystals, replacing the olivine, and in so doing captured the atmospheric carbon dioxide and permanently stored it within the rock. Lafayette provides direct evidence for storage of carbon dioxide in the fairly recent history of Mars, sometimes after 1,300 million years. However, as all of the ingredients for carbonation were present on early Mars - in the form of olivine, water and carbon dioxide - this reaction may explain how carbon dioxide was removed from the planet’s atmosphere changing its climate from warm, wet and hospitable to life, to cold, dry and hostile.

Whilst this process also occurs naturally on Earth, and is the focus of research examining methods of permanently locking up carbon dioxide from power stations, the magnitude of the effect on early Mars indicates that it has the potential to be effective on a planetary scale.