Human missions to Mars will be much more difficult than missions to the moon. Round trip human missions to Mars will require about two years to complete, compared with the eight-day Apollo missions to the moon. Because humans will likely stay on Mars for much longer than they did on the moon, the development of the infrastructure required for a scientific outpost that can sustain humans for long periods of time is critical. Robert L. Ash, professor of aerospace engineering at Old Dominion University (ODU), will speak on “Challenges of Building a Human Outpost on Mars” at a colloquium at 2 p.m., Thursday, May 5, at NASA Langley’s H.J.E. Reid Conference Center.