"In wintertime, the cliff surface gets so cold that its temperature falls below the freezing point of CO2, which at low pressure goes directly to solid, " said Dr Musselwhite.

BBC: Doubts over water on Mars

Jones, Les Claypool, Charlie Musselwhite, thank you so much, gentlemen, for being here. (Applause.) We are all big fans. (Applause.) We are all huge fans of your music, and it is a great honor to have you guys here.

WHITEHOUSE: Remarks by the President at a Campaign Event