The scientists came armed with ideas for a robotic NASA mission using innovative spacecraft that hop, fly, float, roll and dig. By next year, NASA officials hope to select one idea as they prepare to build the new class of robotic spacecraft, called Scouts, for a $300 million mission the space agency intends to launch to Mars by 2007. What the first spacecraft will look like is anyone’s guess, but it is likely to be a departure from the group of orbiters and landers NASA has sent to Mars since the 1960s.