For example, new studies of the rock and soil samples retrieved during the six Apollo expeditions to the moon have raised questions about how Earth's companion formed.
The prevailing theory has been that a Mars-sized object bashed into Earth during the solar system's early days, causing debris to shoot into space. The material eventually collected into what became the moon.
Computer models laying out the impact scenario, however, can't account for traces of water and other lightweight elements found inside volcanic glass beads in the lunar samples. The extreme heat of the collision likely would have vaporized these volatiles.
More clues to the moon's formation, as well as Earth's early history, may lie inside a massive impact crater on the moon's south pole. The so-called Aitken basin juts more than 8 miles into the lunar crust, perhaps even down to the mantle.
"Aitken may have penetrated deep enough into the moon to give us information that ultimately would feed into answering this question," Schmitt said.
In addition to science, the moon presents a relatively nearby place to test equipment and develop technologies needed to go to Mars, a long-term objective of the U.S. space program. Moon missions also would enable a new generation of workers to learn to operate in deep space.
"The people who know how to work in deep space are my age now, if not older," said Schmitt, 77. "We need young people to get the same kind of experience."
A National Research Council report released this week shares Schmitt's concerns.
"We see little evidence that the current stated goal for NASA's human spaceflight program - namely, to visit an asteroid by 2025 - has been widely accepted as a compelling destination by NASA's own workforce, by the nation as a whole, or by the international community," the report said.
Schmitt presented research about ongoing studies of the 40-year old Apollo moon samples at the American Geophysical Union conference in San Francisco this week.