They went to a place a quarter of a million miles from here, stood in funny-looking dust, and came home. It wasn't their fault we badly needed heroes and they had to do. Some now are in business, others' in science and teaching. A few stayed in. A few turned to Jesus. At least one, Buzz Aldrin, cracked in the white glare of fame.

One other became a United States senator.

The last man to walk on the moon is seated on a Capitol Hill barstool. Harrison H. Schmitt, Harvard geologist, former Fulbright fellow, ex-astronaut. "Hi. I'm Jack Schmitt, senator from New Mexico," he says to the bartender, extending a paw, guileless as a Boy Scout.

Jack Schmitt - even his receptionist shrinks from Harrison - has completed his freshman year in the Senate. From all reports the Club hasn't changed him much. He still drives his pickup (a red Ford, in continual need of a bath); still prefers taking trips alone, in coach; still has one of the most modest offices in the Dirksen Senate Office Building. (He halved it to make more room for his staff.)

There are some negatives.

"He doesn't have the social instincts or worldliness most people do," say Eugene Cernan, who rode to the Valley of Taurus-Littrow with Schmitt in 1972. Says Sen. Richard Lugar, friend and fellow Republican from Indiana: "I think it was true for most of our first year, though not in the last few months, that some of the senior senators thought he spoke too often and too long. Jack is more interested in seeing his viewpoint prevail than in being a winsome personality.

Then, too, the technocrat in him gets tiresome. The way you get a bill through Congress, he believes, is the same way you got to the moon - by "critical path analysis." Even male - female relationships are put to scientific analogy: "Lives are like vectors. To make them intersect, you must have the ability for instant compromise."

"There's a reverence for consistency, for logic, for things fitting in their place," says a legislative aide whom Schmitt recently let go. "I don't think he's learned yet you can't be definitive about human beings." This is said with no visible bitterness.

And yet, just when you're convinced there is engine oil in Harrison Schmitt's veins, you discover . . . that he loves stormy Rachmaninoff concertos. That he is a fan of Steinbeck and Richard Brautigan's "Trout Fishing in America." That he's knowledgeable about French (uisine. That he named craters on the moon after the Bronte sisters. Horatio Hornblower, Lara in "Dr. Zhivago."

"The idea was to try to recognize people who had pushed back frontiers of knowledge," he says.

For a while there he was said to keep a pet rock on his desk. (It's in a bottom drawer now, thinks his staff.) He has fiddled with verse. He's an honorary member of Ranger Rick's Nature Club. He has a Ph.D. from Harvard, a B.S. from Cal Tech, the National Order of the Lion from the Republic of Senegal. He is a bachelor with the crisp dark looks of a movie star. He gets seven hours sleep "religiously." He doesn't mind staying home on Saturday nights. He takes the stairs two at a time.

"He treats the staff like a family," says a female aide. "We'll be in the office working late - we're always working late - and he'll call out: 'Who's goint to eat?' I mean, in one way that can really be nice. But in another way it's too . . . chummy."

"The brotherhood of the right stuff." Tom Wolfe called astronauts. "Strange, plasticized, half-fommunicating Americans." said Norman Mailer.

And then, of course, there is the mystique of Harrison Schmitt's pickup. He seems almost to have a thing about his pickup. After his election he drove it cross-country, keeps it parked now in the Senate garage. Not long ago, his tape deck was ripped off. That got him mad.

"Oh, don't be fooled by the pickup," says another aide. He grew up driving them. It's part of life in the West. And he's a geologist. What do geologists do? They collect rocks."

The rock collector, having ordered lunch and denied, to someone down the bar, that he was once a basketball star ("Me? I'm 5 feet 8"), is recapping his first year in politics. A moment earlier Daniel Patrick Moynihan had come into the restaurant in the company of a writer for The New Yorker. The two senators had greeted each other affectionately, Moynihan backclapping and getting off a joke. Not long ago Moynihan said in an interview he was bothered to often be voting against men like Schmitt.

New Mexico's junir senator is in a dark blue suit today, aviator glasses, a rep tie. The thick black hair is mussed. He doesn't look like a son of Silver City, N.M., a desert mining and ranching community (pop. 7,000) that Schmitt has likened to the Texas setting of Larry McMurtry's "The Last Picture Show." (He grew up on 80 acres, the son of a locally prominent geologist and amateur meteorologist. In high school, Schmitt played football, was president of the student council, had the lead in the senior play.)

He looks comfortable in this glossy Eastern bar, one squat leg propped on the rung of his stool. He almost could be Jimmy Stewart on the set of "Mr. Schmitt Goes to Washington."

"It took about a year to get the confidence to know what we could do in the Senate," he says. "We look forward now to hearings on a billwe've introduced, w20-11, the Regulatory Reduction and Congressional Control Act, which would return to Congress its constitutionally mandated legislative authority. At present, there are some 44 independent regulatory agencies with 100,000 employes at a cost of $3.5 million to the taxpayer. I think that's outrageious." The bill grows, he says, out of one of his two cornerstone beliefs: minimum government. The other is individual freedom of choice.

The newly revived Senate Ethics Committee comes up. Schmitt is its ranking minority member. The committee - which is investigating everything from Senate involvement in Koreagate to the abuse of the franking privilege - is wrongheaded, he feels. There's no such thing as being able to legislate ethics.

"The only way this country is going to force ethical conduct is by full disclosure - of travel, of gifts, of contributions. If I were a voter, I think I'd resent six men sitting in judgement of 94 senators and 6,000 Senate employes." For now, Schmitt says, the committee is stuck with trying to enforce a code of conduct.

In a while the talk drifts to the astronaut experience. He's given up flying altogether now. Yet sometimes, on moonlit nights, he can't help gazing up and remembering. After he got back he tried putting some of his feelings in prose poetry. The earth was "that lonesome, marbled piece of blue with ancient seas and continental rafts." He saw "banded sunrises and sunsets changing in a few seconds from black to purple to red to yellow to searing dayling . . ."

"What the flight chiefly did," he says with the faint monotony of someone who's answered this before, "was reinforce an idea I'd long been edging toward: That there is just one fragile spaceship earth, and that if we are to survive, we must all take a world view."

Pause. "There was no discontinuity in my beliefs."

Does he ever miss it? Vigorous shake. "That chapter is over now."

Back to politics. He beat Joseph Montoya, who had been in the Senate two terms, by campaigning up and down New Mexico's 122,000 square miles for 13 months, he says. Montoya had gotten into trouble over tax audits and apparent financial conflict of interest in Santa Fe. Schmitt's statewide billboard slogan: "Honesty . . . for a change."

"I don't think there's a Senate race in this country that's safe in the face of astrategically fought 13-month campaign," he says. "You can win anything if you want it bad enought."

Why did he want it? "Challenge and public service have always been at the bottom of most things I've done." A hesitation. "Then, too, when I was at Harvard I was bothered by how much my ideas were in seeming conflict with the ideas of people from the East. I decided then that someday I'd try getting into politics."

Then, for the first time in several interview sessions, Harrison Schmitt opens up. It is barely for an instant - like the shutter-snap of a camera. He has been talking of the impact the film version of "The Last Picture Show" had on him, and how Sam the Lion's death so reminded him of his own father's.

"You know," he says, beginning slowly, "my dad died an unhappy man. He'd done a lot of reading and thinking and was convinced this country wasn't going to make it. Maybe that's the subliminal reason I entered politics - to try and prove Dad wrong."