The fourth man to walk on the moon, Alan Bean (in 2008), has died at age 86, following a sudden illness. Six years later he became the lunar module pilot in the second U.S. mission to the Moon: Apollo 12.
Bean retired from the Navy in 1975 and NASA in 1981.
NASA Administrator Jim Bridenstine called Bean a boundary pusher who sought to advance limits of technology, science and imagination.
He trained as a Navy test pilot under Conrad, who years later during their astronaut time played a crucial role in getting Bean designated for the Apollo mission. His Apollo-themed paintings featured canvases textured with lunar boot prints and were made using acrylics embedded with small pieces of his moon dust-stained mission patches.
Bean was born in Wheeler, Texas, in 1932 and educated at the University of Texas - graduating in 1955.
Bean and Conrad spent more than 31 hours on the lunar surface, including more than seven hours working outside of the module. Bean is one of only 12 men to have touched the moon's surface.
Many fellow space explorers posted tributes to Bean on Twitter.
Astronaut-artist Alan Bean speaks at the 2009 opening of an exhibit titled "Alan Bean: Painting Apollo, First Artist on Another World" at the Smithsonian's National Air and Space Museum in Washington.
NASA said Bean was one of the third group of astronauts named by NASA in October 1963. "But I've been there and I can tell you it's mostly black dirt".
"I said, 'I'm going to be an artist, '" Bean recalled.
US astronaut Karen Nyberg called Bean a kind, gracious and humble man and a true role model. "And for years, Alan and I never missed a month where we did not have a cheeseburger together at Miller's Café in Houston", Cunningham said.
"Sad day. Not only did we lose a spaceflight pioneer, 4th man to walk on the moon, but also an exceptional artist that brought his experience back to Earth to share with the world". "I feel fortunate to have met him".
Mr Bean's wife Leslie remembered him as "the strongest and kindest man I ever knew", adding: "He was the love of my life and I miss him dearly". He is survived by his wife, sister and two children from a prior marriage.
In 1994 Bean told The New York Times the otherworldly perspectives he got in space inspired him to devote the latter half of his life to art, to the surprise of many of his colleagues.