WASHINGTON — Alan Bean has checked the actuarial tables and knows the chances of the three Apollo 11 astronauts being around for the 50th anniversary of the first moon landing are slim, as in no better than 5 percent. That, he says, is another reason why this week's 40th anniversary celebration is so important to him, the rest of the surviving moon walkers and legions of Apollo engineers and technicians.

Bean, the fourth man to walk on the moon aboard Apollo 12 in October 1969, also happens to be the only artist who paints the lunar surface based on personal observation. The Apollo and Skylab veteran who spent more than 69 days in space shocked his colleagues in 1981 by retiring from NASA, rolling the dice and taking up painting full time. He immediately set to work trying to depict his experiences walking on the moon and the meaning of Apollo. His tools are textured acrylic paint, moon dust, bits of his spacesuit and spaceship. Each was applied and embedded on canvas, airplane plywood and masonite.

He's still at it at the age of 77.

In conjunction with the 40th anniversary of the first moon landing, the Smithsonian National Air and Space Museum has mounted a retrospective of Bean's moon paintings under the direction of Smithsonian curator Carolyn Russo. Certainly for space enthusiasts, and perhaps for art lovers as well, the exhibition succeeds in showing the progression of Bean's hard work, which intentionally or unintentionally, melds esthetics with technology while seeking to preserve the Apollo story for posterity.

Bean pursued his art in the same dogged fashion that he trained to become an astronaut. In discussing his decision to leave NASA and paint full time, Bean recalled: "I didn't see anybody around of the 12 of us who got the gift of walking on the moon interested in telling these stories this way. I said, 'You know, I'm not the greatest artist in the world, but if I left [NASA] and concentrated, I might be able to do some paintings that would tell stories that would be lost forever if I didn't tell them'."

Some of those stories are best told, he adds, "in books, but some others maybe are best told in paintings."

Bean took some heat from his fellow astronauts for his decision to pursue painting. "Do you think that's worthy, being an artist? Look at the training you've had, the education" to become an astronaut, Bean remembered them saying. Eventually, his NASA colleagues came to appreciate Bean's work, realizing he was "preserving in a different way the great adventure that we were lucky enough to be part of."

Bean readily acknowledges his shortcomings as an artist, but how many artists are painting their memories of walking on the moon? The former test pilot's unabashed enthusiasm for his art (he still sketches and paints at least six days a week and produces as many as seven works a year) was evident as he walked through the Smithsonian gallery where 50 of his paintings and drawings were displayed, along with some of the Apollo hardware used both as backdrops and as painter's tools.

Bean wants to tell stories in his paintings, and has used some to create lunar scenes that didn't happen, although the artist wishes they had.

For example, there are few pictures of Apollo 11 commander Neil Armstrong on the moon since he, not Buzz Aldrin, carried the camera. Bean used the iconic photo of Aldrin on the surface with Armstrong reflected in his gold visor as the starting point to paint the reverse image of Armstrong taking the picture of Aldrin. Bean said he studied training videos of Armstrong to get his body position just right, and worked out the lighting angles by studying other photos. He then built models and painted the picture of Armstrong, called "First Men: Neil Armstrong" (below).

"First Men: Neil Armstrong," 2007, 40 by 30 inches, textured acrylic with moondust on aircraft plywood, by Alan Bean