Propellant preservation for Mars missions

There has been extensive technology planning in the last few years for human missions to Mars. The human missions will make extensive use of cryogenic propellants. Some of these propellants will be transported to Mars. Additional propellants will be manufactured, liquefied, and stored on Mars. The missions that use these propellants could start as early as 2011. While many of the plans are still evolving, it has been possible to derive a set of cooler requirements. Recent estimates of these requirements are given here along with a discussion of whether the requirements can be met with existing coolers and coolers currently being developed.