This week’s report of buried oceans of ice on Mars may spur dreams of human missions to the Red Planet, but nobody is likely to go for 20 years or more, and one expert thinks it would be a bad idea even then. However, such opposition — and the lack of any U.S. commitment to conduct a human mission to Mars — has not stopped NASA from developing a detailed scenario. The scenario, available online at http://nssdc.gsfc.nasa.gov/planetary/mars/marslaun.html, is based on the most optimistic guesses about how such a mission could take place and foresees the launch of the first crew in November 2009. The astronomer who oversees the site, David Williams, said the scenario is based on a 1997 report that presumed work toward a Mars mission would start that year. It did not, so any estimates would have to be pushed back by five years at least.