It has been 50 years since NASA's Mariner 2 spacecraft traveled 36 million miles to Venus for the first-ever close-up view of another planet.

This is a big milestone. Not only did that mission mark the beginning of interstellar exploration, but it also came at a time when morale was low: The U.S. hadn't truly had a space "first" in five years. Meanwhile, as America's space program stood stagnant, the Soviet Union continued to advance its efforts in space.

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NASA recently released an online interactive map where you can relive this milestone and other big moments in space exploration, from 1962 through Curiosity's landing this year.

We all probably remember the major space headlines, but what about the cool stuff that we didn't hear about? What were NASA employees' favorite memories? Mashable asked five Jet Propulsion Laboratory workers to share the space moments they will never forget. Here are their stories in their own words.

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Rob Manning, Chief Engineer, Mars Science Laboratory Mission

At 10:30 a.m. on the Fourth of July in 1997 at the Jet Propulsion Laboratory in Pasadena, Calif., as head of the entry, descent and landing team and Chief Engineer, I was staring at a computer screen watching a series of dramatic events flip by that had been unfolding millions of miles away.

Mars Pathfinder, with the little Sojourner rover safely tucked inside, was landing on Mars. On my headset, I was straining to hear my colleagues on the other side of the Earth in Madrid who were watching analog displays showing signals from Mars via a massive dish antenna.

"I have all eyes watching," Sami Asmar says, only seconds after the time my display has predicted that the lander should be bouncing in its airbag cocoon. "We see a weak signal," he says. "A signal is barely visible!" I repeat it into my microphone while being watched by perhaps millions of people. I knew then that Pathfinder had run the gauntlet and had made a safe contact with the surface on another planet.

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NASA Employees Share Inspiring Stories You've Never Heard