The astronauts, who first landed on the moon, have urged mankind to take a giant leap to Mars.
In one of their few joint public appearances, the crew of Apollo 11 spoke on the eve of the 40th anniversary of man's first landing on the moon, but avoided nostalgia.
They instead spoke about the future and the more distant past.
On Monday, the three astronauts will get another chance to make the pitch for a Mars trip, this time to someone with a little more sway: President Barack Obama.
A packed crowd at Washington's Smithsonian Institution's National Air and Space Museum - 7,000 people applied in a lottery for 485 seats - didn't get the intimate details of the Eagle's landing on the moon with little fuel left, or what the moon looked like, or what it felt like to be there.
They got second man on the moon Buzz Aldrin's pitch for Mars.
He said the best way to honour the Apollo astronauts "is to follow in our footsteps; to boldly go again on a new mission of exploration".
First man on the moon Neil Armstrong only discussed Apollo 11 for about 11 seconds.
He gave a professorial lecture titled "Goddard, governance and geophysics", looking at the inventions and discoveries that led to his historic "small step for a man" in the early hours UK time of July 21, 1969.
