University of Minnesota
July 15, 2009
Physics professor Bob Pepin has studied moon rocks like this sample (in center of gray cylinder) from the historic Apollo 11 mission.
Photo: Patrick O'Leary
Physics professor Bob Pepin recalls his roles in NASA's moon landings
By Deane Morrison
After their flight from Houston landed in the Twin Cities one day in August 1969, two University of Minnesota professors had to stay in the rear of the plane until a couple of policemen came to escort them off.
For physicist Bob Pepin, it was an awkward moment.
"I'm sure they [bystanders] thought we were criminals, because that's the way they treated [us]," he says.
A laughable thought for anyone who knows the genial Pepin. That day he and his companion, now-retired geology professor Rama Murthy, were singled out because they were carrying a priceless cargo: samples of moon rocks collected by Neil Armstrong and Buzz Aldrin after their historic landing on July 20, 1969.
Forty years later, Pepin, newly retired but still active in research, remembers well the roles he played in NASA's Apollo program and says the moon landings yielded a wealth of information about the solar system. Perhaps more important, though, was its psychological impact.
'It was the first chance to look at another planet," he says. And while plenty remains to be learned about the moon, he believes the best reason for returning is our satellite's value as a stepping stone to Mars.
Superb science, dysfunctional drill
A few years before the moon landing, Pepin and Murthy were among the scientists worldwide selected to receive moon rock samples for research. Soon Pepin joined the committee that reviewed requests for samples, including requests from committee members themselves.
A bunch of foxes guarding the henhouse? Not really. "It was a great experience. We monitored each other," Pepin explains.
He was asked to join a second NASA committee, the Science Working Group, which designed lunar surface activities and trained astronauts to perform them. Pepin stayed on both committees till the end of the Apollo program and also served as science adviser to the last four Apollo missions--14 through 17--at Mission Control in Houston.
The moon appears bone dry, but some scientists think it may contain ice. How could it get there? Maybe by special delivery, says University astronomy professor Terry Jones. "Comets hit every now and then, and they contain water," he says. "Some might freeze on the surface in craters in permanent shadow near the poles, especially the south pole."
Jones also notes that the return to the moon could become a space race again because China has expressed interest. Scientists, says Jones, tend to prefer space exploration by less expensive robotic probes, but "we also understand that the public likes to see people in space."
In studying the dust that lies 25-35 feet thick on the lunar surface, Pepin and investigators at other institutions learned "a lot more about the sun than the moon." They found pieces of the sun--tiny particles that stream out continually in the "solar wind"--embedded in the dust. Among the particles was the lighter form of helium, called helium-3.
"It's regarded as the perfect fusion fuel," says Pepin. "But is it a viable fusion source? It would have to be mined and shipped."
Pepin credits the moon rocks with helping to solve one of science's biggest mysteries: Where did the moon come from? Some believed it formed along with Earth, from the same cloud of primordial gas; others thought it formed elsewhere and wandered into Earth's gravitational field.
As it turns out, the moon was born in an even more dramatic event. When Earth was a few tens of millions of years old, a projectile the size of Mars collided with it. Molten rock from Earth and the "impactor" was flung into space and coalesced into the moon. Impactor material wound up in both bodies.
"As nearly as we're sure of anything, we're sure of this," says Pepin. "Many moon rocks looked just like the mantle of Earth. That showed that the moon is partly made of Earth materials."
As science adviser at Mission Control, Pepin stood by in case an astronaut on the moon had a question. It happened only once--during Apollo 15, the first mission where astronauts tried to drill out a core of lunar soil. All went well for the first three meters, then the drill got stuck.
Mission commander Dave Scott wanted to leave the drill and head for a crater he had his heart set on exploring. But the astronauts couldn't do both. Mission Control threw the decision to Pepin.
He recalls the moment: "Every eye turned to me: 'All right, Pepin, earn your keep. Do we try to get it out or leave it in?' I said, 'Let's try to get it out.' They [astronauts] weren't very happy. Scott worked so hard, his heart went into arhythmia."
But the drill, with its core of sediment, did come out. Later, the astronauts' perseverance paid off doubly. First, X-rays of the core revealed "lovely depositional layers" of lunar soil that had settled after being ejected by meteorite hits. Second, physicians realized that a lack of dietary potassium had caused Scott's cardiac arhythmia. In future flights, NASA upped the potassium to the benefit of astronauts' health. Their taste buds were a different story.
"On the next mission, John Young and his colleagues had orange juice laced with potassium salts," recalls Pepin. "They were sitting in the [lunar] lander after a [moon walk], talking about the orange juice, and they obviously didn't realize the microphone was on. Some of the things they said about it I couldn't repeat."
What most bugged the astronauts, though, was the moon dust.
"It was electrically charged, and it clung to everything--their spacesuits, their boots, and even their sandwiches," says Pepin. "I expect they ate a lot of it."
Springboard to Mars
The moon still guards secrets, such as whether ice has accumulated in permanently shadowed craters near the poles. A search for ice and future landing sites is now under way by the Lunar Reconnaissance Orbiter, launched by NASA June 18. Pepin, who has no doubt people will eventually return to the moon, says the main driving force isn't science, but finding out whether "another leap outward" from Earth is feasible.
"Clearly, Mars has water," he notes. "But it has a real problem with [unshielded] ultraviolet light and other things. The moon is a good test bed. I see 20 to 30 years before we have a trip to Mars. I think we'll find evidence of life if we get there."
Why go at all?
"There's always some subsection of the population that has the exploring urge," Pepin muses. "I think the real reason is they just want to find out what's there."
Read about Pepin's recent work on NASA's Stardust mission.