The gas that used to be in the atmosphere has been removed entirely from the planet. It’s not locked up in the crust, it’s not in the polar caps – it’s gone,” said Jakosky. “One of the problems has always been focused on looking within the crust for a reservoir of carbon-bearing minerals, and they haven’t found it. So I think this really resolves one of the fundamental issues about Mars, where did the volatiles go, all the carbon dioxide.”