Alan Bean—the fourth human to walk on the Moon, one of the first Americans to live aboard a space station, and a man who left space flight behind to devote the second half of his life to painting—died on Saturday in Houston. He was 86.

With Bean's passing, just four living human beings have walked on the Moon: Buzz Aldrin, 88; Dave Scott, 85; Charlie Duke, 82; and Harrison Schmitt, 82. The eight other humans who landed on the Moon in the late 1960s and early 1970s during NASA's Apollo Program have died, as have all of the original seven astronauts in the Mercury space program.

After Bean earned an engineering degree from the University of Texas at Austin, he was commissioned in the US Navy and became first an aviator and later a test pilot. NASA selected him as a member of its third class of astronauts in 1963. Following his astronaut training and a few stints as a back-up crew member, Bean received his assignment as the lunar module pilot for Apollo 12, which became, in November 1969, NASA's second mission the Moon's surface.

Saving Apollo 12

Bean proved his value to the mission just seconds after the Saturn V rocket carrying the Apollo Command Module and Lunar Module lifted off from the ground. That's when the large booster was struck by lightning. The lightning strikes knocked many of the sensors and instruments inside the Apollo Command Module offline, and the spacecraft began transmitting nonsensical telemetry data to the ground. More troubling, the lightning had wiped out the Command Module's carefully calibrated guidance and navigation platform. Shortly after the strikes, the mission's commander, Pete Conrad Jr., called down to Houston.

"OK, we just lost the platform, gang," Conrad said. "I don't know what happened here; we had everything in the world drop out."

In one of the more celebrated moments in Mission Control's history, a flight controller named John Aaron recalled seeing a similar pattern of nonsense telemetry data when the power supply to a piece of hardware inside the Command Module called the "Signal Conditioning Equipment" (SCE) had failed. Aaron deduced that switching this SCE box to its backup mode would bring it back online.

"Try SCE to Aux," Aaron told the Apollo 12 flight director, Gerry Griffin. Griffin didn't recognize the command but agreed to have it relayed up to the Command Module. Conrad, the mission commander, didn't recognize it either. Bean, however, did. He found and flipped the appropriate switch. Almost immediately, Mission Control began receiving good telemetry data, which gave Griffin the data he needed in order to clear the crew to continue its flight to orbit. (The incident is dramatized with a reasonably high degree of accuracy in an episode of the 1998 HBO miniseries From the Earth to the Moon.)

Audio from inside the Command Module reveals that, just minutes after this near disaster and even before the crew had reached orbit, the level-headed astronauts were joking about the incident. A few days later, NASA had landed safely on the Moon for a second time.

Bean would fly into space a second time in 1973 as part of the second crewed mission to the Skylab space station. With two other crew members, he spent 59 days in space as NASA expanded its science activities in low Earth orbit and began experimenting with long-duration spaceflight.

Bean remained at NASA throughout the 1970s but left the space program in 1981, just as the new space shuttle was making its maiden flight and kicking off a new phase of human spaceflight.

Astronaut to art

"I loved being an astronaut; I was thinking about flying the space shuttle, but I said you know there are a lot of young men and women around who can fly the space shuttle just as good as I can or better," he later recalled. "But there's no one around that's been to the Moon, that took part in one of humankind's great adventures, that wants to represent it in another way."

That other way was painting. The Apollo astronauts, of course, had done a comprehensive job of capturing their experiences on the Moon in still photos, video, and audio. But having been there, Bean felt that art could capture the spirit of Apollo in another, more human way.

His paintings showed astronauts doing some of the things they'd actually done, and some they wished they'd done. (For example, in The Fantasy, Apollo 12 Command Module pilot Richard Gordon stands alongside Bean and Conrad on the lunar surface). Although the Moon was a stark, gray place, Bean added the color of human imagination in his paintings.

Shuttle astronaut Nicole Stott, who also pursued art after retiring from NASA, told Ars the following:

I am heartbroken to learn of this world's loss of Alan Bean. One of the greatest compliments I've ever received is when he called me a kindred spirit. This was a bit overwhelming since he is one of my heroes—one of my superheroes, actually, of spaceflight and art. I first met him shortly after I retired from NASA to pursue my next adventure as an artist. He welcomed me to his studio, he shared his own story of transition from astronaut to artist, he walked me through his whole creative process for his beautiful paintings, and he encouraged me to pursue the art I love. I am so thankful for a mentor and friend like Alan Bean. I will always cherish his thoughtfulness and his wonderful smile, and we are all blessed by the legacy of his amazing artwork.

After leaving NASA, most of the other Apollo astronauts moved on to other locations. Bean remained in Houston near Johnson Space Center, where he established his art studio. Through his paintings, he hoped to inspire future explorers of the Moon, Mars, and elsewhere to not only boldly go to these frontiers but also to bring a little whimsy and humanity with them as they went.