The second American to orbit the Earth and one of the last surviving original Mercury 7 astronauts has died.
Astronaut Scott Carpenter was 88.
As an astronaut and aquanaut who lived underwater for the US Navy, Carpenter was the first man to explore both the depths of the ocean and the heights of space.
Three months later, Carpenter orbited the Earth three times. He lost contact with Nasa during the off-target landing but was found safely floating in his life raft 288 miles away.
Carpenter and Glenn were the last survivors of the original Mercury 7 astronauts from the "Right Stuff" days of the early 1960s.
Nasa administrator Charles Bolden said Carpenter "was in the vanguard of our space programme - the pioneers who set the tone for our nation's pioneering efforts beyond Earth and accomplished so much for our nation. We will miss his passion, his talent and his lifelong commitment to exploration."
Life was an adventure for Carpenter and he said it should be for others: "Every child has got to seek his own destiny. All I can say is that I have had a great time seeking my own."
The launch into space was nerve-racking for the Navy pilot on the morning of May 24, 1962.
"You're looking out at a totally black sky, seeing an altimeter reading of 90,000 feet and realise you are going straight up. And the thought crossed my mind: What am I doing?," Carpenter said 49 years later in a joint lecture with Glenn at the Smithsonian Institution.
For Carpenter, the momentary fear was worth it, he said in 2011: "The view of Mother Earth and the weightlessness is an addictive combination of senses."
For the veteran Navy officer, flying in space or diving to the ocean floor was more than a calling. In 1959, soon after being chosen as one of Nasa's pioneering seven astronauts, Carpenter wrote about his hopes: "This is something I would willingly give my life for."
"Curiosity is a thread that goes through all of my activity," he told a Nasa historian in 1999. "Satisfying curiosity ranks number two in my book behind conquering a fear."
Even before Carpenter ventured into space, he made history on February 20, 1962, when he gave his Glenn send-off. It was a spur of the moment phrase, Carpenter later said.
"In those days, speed was magic because that's all that was required ... and nobody had gone that fast," Carpenter explained. "If you can get that speed, you're home free, and it just occurred to me at the time that I hope you get your speed. Because once that happens, the flight's a success."
Three months later, Carpenter was launched into space from Cape Canaveral, Florida, and completed three orbits around Earth in his space capsule, the Aurora 7, which he named after the celestial event. It was just a coincidence, Carpenter said, that he grew up in Boulder, Colorado, on the corner of Aurora Avenue and 7th Street.
His four hours, 39 minutes and 32 seconds of weightlessness were "the nicest thing that ever happened to me", Carpenter told a Nasa historian. "The zero-G sensation and the visual sensation of spaceflight are transcending experiences and I wish everybody could have them."
His trip led to many discoveries about spacecraft navigation and space itself, such as that space offers almost no resistance, which he found out by trailing a balloon. Carpenter said astronauts in the Mercury programme found most of their motivation from the space race with the Russians. When he completed his orbit of the Earth, he said he thought: "Hooray, we're tied with the Soviets," who had completed two manned orbits at that time.
Things started to go wrong on re-entry. He was low on fuel and a key instrument that tells the pilot which way the capsule is pointing malfunctioned, forcing Carpenter to manually take over control of the landing.
Nasa's Mission Control then announced that he would overshoot his landing zone by more than 200 miles, and worse, they had lost contact with him.
Talking to a suddenly solemn nation, CBS newsman Walter Cronkite said, "We may have ... lost an astronaut."
Carpenter survived the landing.
Always cool under pressure - his heart rate never went above 105 during the flight - he oriented himself by simply peering out the space capsule's window. The Navy found him in the Caribbean, floating in his life raft with his feet propped up.
Carpenter's perceived nonchalance did not sit well some with Nasa officials, particularly flight director Chris Kraft. The two feuded about it from then on.
Kraft accused Carpenter of being distracted and behind schedule, as well as making poor decisions. He blamed Carpenter for low fuel.
On his website, Carpenter acknowledged that he didn't shut off a switch at the right time, doubling fuel loss. Still, Carpenter in his 2003 memoir said: "I think the data shows that the machine failed."
In the 1962 book We Seven, written by the first seven astronauts, Carpenter wrote about his thoughts while waiting to be picked up after splashing down.
"I sat for a long time just thinking about what I'd been through. I couldn't believe it had all happened. It had been a tremendous experience, and though I could not ever really share it with anyone, I looked forward to telling others as much about it as I could. I had made mistakes and some things had gone wrong. But I hoped that other men could learn from my experiences. I felt that the flight was a success, and I was proud of that."
One of 110 candidates to be the nation's first astronauts, Carpenter became an instant celebrity in 1958 when he was chosen as a Mercury astronaut. Like his colleagues, Carpenter basked in lavish attention and public rewards, but it was not exactly easy. The astronauts were subjected to gruelling medical tests - keeping their feet in cold water, rapid spinning and tumbling and open-ended psychological quizzes. He had to endure forces 16 times gravity in his tests, far more than in space, something he said he managed with "great difficulty".
"It was the most exciting period of my life," he said.
Carpenter never did go back in space, but his explorations continued. In 1965, he spent 30 days under the ocean off the coast of California as part of the Navy's SeaLab II programme.
"I wanted, number one, to learn about it (the ocean), but number two, I wanted to get rid of what was an unreasoned fear of the deep water," Carpenter told the Nasa historian.
Inspired by Jacques Cousteau, Carpenter worked with the Navy to bring some of Nasa's training and technology to the sea floor. A broken arm kept him out of the first SeaLab, but he made the second in 1965. The 57ft by 12ft habitat was lowered to a depth of 205ft off San Diego. A bottlenose dolphin named Tuffy ferried supplies from the surface to the aquanauts below.
"SeaLab was an apartment but it was very crowded. Ten men lived inside. We worked very hard. We slept very little," Carpenter recalled in a 1969 interview. Years later, he said he actually preferred his experience on the ocean floor to his time in space.
"In the overall scheme of things, it's the underdog in terms of funding and public interest," he said. "They're both very important explorations. One is much more glorious than the other. Both have tremendous potential."
After another stint at Nasa in the mid-1960s, helping develop the Apollo lunar lander, Carpenter returned to the SeaLab programme as director of aquanaut operations for SeaLab III.
He retired from the Navy in 1969, founded his company Sea Sciences, worked closely with Cousteau and dove in most of the world's oceans, including under the ice in the Arctic.
When 77-year-old Glenn returned to orbit in 1998 aboard space shuttle Discovery, Carpenter radioed: "Good luck, have a safe flight and ... once again, Godspeed, John Glenn."