NASA Administrator Daniel S. Goldin told the MIT Class of 2001 yesterday they can expect to help put an American astronaut on Mars within 20 years, but one NASA watcher said the political will for a Mars trip is still lacking. “You will make my dreams come true. Not in 50 years, but in 20,” Goldin told the 2,369 graduates. “A spacecraft will land. A hatch will open. A ladder will drop. Then, the world will watch as an astronaut – in a white suit with an American flag on the shoulder – steps down, and crunches her boot down on the dusty red surface of Mars.”