The surviving members of the Apollo 13 Moon mission have called on President Obama to continue with the US's space program, on the 40th anniversary of the dramatic lunar expedition.
Jim Lovell and Fred Haise marked the anniversary of the Apollo 13 mission at the Adler Planetarium in Chicago.
The third member of their 1970 mission, Jim Swigert, died in 1982.
Lobbying Congress
The retired astronauts urged the American public to lobby Congress in order to overturn President Barack Obama's plans to cut funding to NASA's Constellation program.
Obama has been tightening the belt as the US recovers from the global financial crisis.
But Lovell says the cost of the program should not be a factor.
"This is a creative programme. It's a programme that tries to generate new knowledge of our own being, our Earth, our solar system ... the spin-offs are tremendous," he told British newspaper The Times.
Obama is due to give a speech defending his program in the next few days.
Oxygen tank burst
In 1970, as the three-man Apollo 13 crew were four-fifths of the way to the Moon, an oxygen tank aboard Apollo 13 burst.
The crew were forced to abort their mission and return to Earth.
Their against-the-odds survival is considered one of the greatest triumphs in the history of space exploration.
Lovell's legendary words to Mission Control after the explosion have entered the common vernacular: "Houston, we've had a problem" – now widely recited as "Houston, we have a problem".
A movie starring Tom Hanks was made in 1995 on the mission.
