NASA has been warned in a new report that it is falling short on its requirements for future Mars exploration, especially if it wants to translate future robotic missions into a manned attempt to visit the planet. The report from the National Research Council, which advises the government on science issues, was requested by NASA itself, so the findings will hopefully have weight with officials. Plans for the next decade get a broadly positive report, but the main problem for NASA is that billions of dollars have been stripped from their science budget in order to keep the Shuttle and International Space Station in operation. One of the biggest casualties has been a sample return mission, which is not likely to happen now until the early 2020's. Complex detailed robotic missions such as this are vital to improving our understanding of the planet, given that astronauts may need to spend a year on the surface.