It was 43 years ago on Friday that Neil Armstrong and Edwin "Buzz" Aldrin, two members of the Apollo 11 crew, became the first humans to set foot on the moon.

As more than 500 million people watched on television, Commander Armstrong stepped out of the lunar module Eagle and said the now iconic words:

"That's one small step for a man, one giant leap for mankind."

The Saturn V rocket carrying the Apollo 11 crew had blasted off from Florida about 109 hours earlier.

The two astronauts spent just over 21 hours on the moon before returning to the orbiting Columbia module to begin their journey back to Earth. They brought with them almost 50 pounds of geological samples, according to the Lunar and Planetary Institute.

The two men, along with Command Module Pilot Michael Collins, splashed down safely in the Pacific Ocean on July 24, 1969.

It was the realization of a goal that President John F. Kennedy had set eight years earlier in a speech to Congress:

First, I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the moon and returning him safely to the earth. No single space project in this period will be more impressive to mankind, or more important for the long-range exploration of space; and none will be so difficult or expensive to accomplish.

It's been almost 40 years since a person last walked on the moon, and NASA now has its sights set on Mars. Next month, the Curiosity rover, which is about the size of a small SUV, is expected to land there, and NASA is developing a heavy lift rocket that it hopes will one day take humans to the red planet.

LOOK: Pictures from Apollo 11:

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  • Going Up

    FILE - In this July 16, 1969 file photo provided by NASA, the Saturn V rocket that launched Neil Armstrong, Buzz Aldrin and Michael Collins on their Apollo 11 moon mission lifts off at Cape Kennedy, Fla. For more than four decades, the powerful engines that helped boost the Apollo 11 mission to the moon have rested in the Atlantic. Now Internet billionaire and space enthusiast Jeff Bezos, CEO of Amazon.com, wants to raise at least one of them to the surface. (AP Photo/NASA, File)

  • APOLLO 11 MOON LANDING

  • FILE - This July 20, 1969 file photo provided by NASA shows Apollo 11 commander Neil A. Armstrong inside the Lunar Module while on the lunar surface. Astronauts Armstrong and Edwin E. Aldrin Jr., lunar module Pilot, had already completed their extravehicular activity when this picture was made. First moonwalker Armstrong, first American in orbit John Glenn, Mission Control founder Chris Kraft, Apollo 13 commander Jim Lovell, first shuttle pilot Robert Crippen and others are pushing for a last minute reprieve for the about-to-be-retired space shuttle fleet. (AP Photo/NASA, file)

  • These NASA handout images show at top th

    These NASA handout images show at top the Apollo 11 lunar landing astronaut crew from left: Neil A. Armstrong, Michael Collins, and Edwin E. 'buzz' Aldrin Jr. At bottom from left are Edwin E. 'Buzz' Aldrin, Michael Collins, Neil Armstrong on the eve of the 40th anniversary of Apollo 11's first human landing on the Moon at the National Air and Space Museum in Washington, on July 19, 2009. AFP PHOTO / NASA == RESTRICTED TO EDITORIAL USE / NO SALES == (Photo credit should read /AFP/Getty Images)

  • In this NASA handout picture taken in Ju

    In this NASA handout picture taken in July 16, 1969, the American flag heralds the flight of Apollo 11, the first Lunar landing mission. The Apollo 11 Saturn V space vehicle lifted off with astronauts Neil A. Armstrong, Michael Collins and Buzz Aldrin, at 9:32 a.m. July 16, 1969, from Kennedy Space Center's Launch Complex. During the planned eight-day mission, Armstrong and Aldrin will descend in a lunar module to the Moon's surface while Collins orbits overhead in the Command Module. The two astronauts are to spend 22 hours on the Moon, including two and one-half hours outside the lunar module. AFP PHOTO NASA (Photo credit should read /AFP/Getty Images)

  • Buzz Aldrin Poses next To The U.S. flag On Moon

    060280 01: Astronaut Edwin 'Buzz' Aldrin poses next to the U.S. flag July 20, 1969 on the moon during the Apollo 11 mission. (Photo by NASA/Liaison)

  • The space crew of the Apollo 11 mission

    The space crew of the Apollo 11 mission sits in front of cameras answering journalists questions during the night before the liftoff at Kennedy Space Center, Florida, on July 16, 1969. From left to right : Lunar module pilot Buzz Aldrin Jr, Commander Neil A. Armstrong, command module pilot Michael Collins. AFP PHOTO NASA (Photo credit should read /AFP/Getty Images)

  • US Vice-President Spiro Agnew and former

    US Vice-President Spiro Agnew and former US President Lyndon B. Johnson are seen in a crowd watching the liftoff of the Apollo 11 mission at Kennedy Space Center, Florida, on July 16, 1969. AFP PHOTO NASA (Photo credit should read /AFP/Getty Images)

  • Aldrin assembles seismic experiment

  • Apollo 11 astronauts, still in their quarantine van, are greeted by their wives upon arrival at Ellington Air Force Base on July 27, 1969

  • LM ladder and commemorative plaque

  • Mission Control celebrates after splashdown, July 24, 1969.

  • Closeup of Earth and terminator.

  • Flag and TV camera viewed from LM window

  • Armstrong photo of LM from a distance

  • Aldrin poses for portrait.

  • Aldrin stands beside LM strut and probe

  • Neil Armstrong works at the LM

  • Aldrin carries experiments for deployment

  • Aldrin on the LM footpad.

  • Lunar module pilot Edwin "Buzz" Aldrin

  • Flight controllers during lunar module descent

  • Aldrin's boot and footprint in lunar soil.

  • Earthrise viewed from lunar orbit prior to landing

  • Apollo 11 liftoff from launch tower camera

  • Apollo 11 Saturn V on launch pad 39A.

  • Crater 308 viewed from orbit.