Two months ago, former NASA astronaut Scott Parazynski ascended Mount Everest, carrying a lunar rock brought back by the Apollo 11 mission that landed on the moon 40 years ago Monday. Along the way, he endured hardships like those experienced by Neil Armstrong and Buzz Aldrin: bulky equipment, rocky terrain and a lack of oxygen.

The effort made Parazynski the first astronaut to summit the world’s highest peak. It also gave him a deeper understanding of why his boyhood heroes of Armstrong and Edmund Hillary sought the unknown.

“Any time you explore … you learn things you never expected,” said Parazynski. “Any country that doesn’t explore is going to ultimately recede.”

That faith that exploration brings its own rewards is the fundamental rationale behind NASA’s efforts to return astronauts to the moon by 2020. For by most other standards — cost, safety and scientific gain — the benefits are dubious.

“Sure, we could go back. But is that the best thing we could do?” asked Aldrin, the second man to walk on the moon. “I would never stoop to call kicking up dust on the moon a stunt, but it certainly wasn’t a pioneering effort that led to sustainment.”

In a few months, President Barack Obama is expected to decide what to do about NASA, an agency he’s said is “adrift.” Perhaps the most pressing issue is its moon mission, an effort so riddled with problems that an independent panel has been asked to review it.

The panel will present its findings next month. It could help answer a question that has divided the nation’s space community for years: why send astronauts back to the moon?

NASA’s decision to return to the moon began with the 2003 Columbia accident.

The tragedy killed seven astronauts and shook confidence in the aging space shuttle. Investigators urged that NASA test every screw, tile and wire in the shuttle fleet if it wanted to fly beyond 2010 — a costly undertaking.

Instead, then-President George W. Bush told NASA in January 2004 to retire the shuttle by 2010 and build a new spacecraft capable of reaching the moon. The goal was to establish a lunar outpost as a stepping-stone for an eventual mission to Mars.

“Returning to the moon is an important step for our space program. Establishing an extended human presence on the moon could vastly reduce the cost of further space exploration, making possible ever more ambitious missions,” Bush said.

To make that vision a reality, former NASA Administrator Michael Griffin selected a new spacecraft system, dubbed Constellation, and set up an office to prepare for lunar missions.

John Olson leads that effort. Like many NASA employees, he was inspired by the Apollo 11 landing. “It taught us that nothing is impossible. That might be the single greatest benefit that came out of it,” said Olson.

“The moon has so much to teach us about the evolution of the Earth,” said Alan Stern, a planetary scientist and former NASA official. Its geology is unchanged since it was formed 4.6 billion years ago when Earth collided with a planet-sized object.

Stern said astronauts are essential to do complex research, such as drilling deep into lunar rock to probe its geologic history.

But others question how much could be gleaned from another moon expedition.

A 2007 report by the National Academies concluded that the “expense of human exploration cannot likely be justified on the basis of science alone” and instead suggested that NASA pursue a “vigorous near-term robotic exploration program.”

Congress remains skeptical, especially in the midst of the worst economy since the Great Depression.

At the confirmation hearing for Charles Bolden, Obama’s pick to run NASA, U.S. Sen. Jay Rockefeller, D-W.Va., warned that NASA must justify its funding: “NASA is not a given,” he warned.

Government auditors have estimated that NASA’s moon plans would cost $230 billion through 2025 — or most of the funding at an agency budgeted at $18.7 billion next year.