Since the end of the Apollo Moon landings more than three decades ago, NASA, with the space shuttles and now the International Space Station, has toiled in Earth orbit a few hundred miles off the ground.

A subcommittee of the panel studied several possibilities, including NASA’s current program to send astronauts back to the Moon by 2020, a more ambitious plan to skip the Moon and aim directly for Mars and what the members called the “flexible path,” which would avoid the “deep gravity wells” of the Moon and Mars, saving the time and cost of developing landers to carry astronauts to the surfaces of those bodies.

Edward F. Crawley, a professor at the Massachusetts Institute of Technology who headed the subcommittee, said, “The flexible path essentially goes across stepping stones” of progressively longer, more challenging missions by which NASA would learn how to operate long missions in deep space.

A flyby of the moon might be followed by more distant trips to so-called Lagrange points, first to the location where the gravity of the Moon and the Earth gravity cancel each other out, then to where the gravity of the Earth and Sun cancel out. There could also be visits to asteroids or flybys of Mars leading to landings on one or both of the low-gravity moons of Deimos and Phobos.

This approach, Dr. Crawley said, would provide “the most steady cadence of steady improvement.”

That approach could also improve the capability of robotic explorers on Mars. Instructions from controllers on Earth now take several minutes to reach craft on Mars. But astronauts on a Martian moon could operate robots on the planet in real time.