What did the Apollo 11 astronauts see on the moon that had them so shaken up?

It’s hard to imagine how primitive computer technology was in 1969. Mission Control's total computing power was the equivalent of an old laptop and the lunar module’s computing capability was equivalent to a digital watch with a calculator. Couple analog technology with human errors and mechanical failures and it is a miracle that Neil Armstrong and Buzz Aldrin ever made it back alive. The White House had prepared a speech honoring the deaths of the astronauts during lunar insertion.

Apollo 11 was four minutes into its landing sequence when Neil Armstrong notified Mission Control of a “program alarm”:

An Error code “1202” was reported to controllers in Houston. Engineers scrambled to unscramble what the error code signified. The code was an indication that more information was coming than could be processed. Time was a luxury that Eagle did not have. Aldrin was losing contact with Houston forcing him to adjust the antenna, but the radio connection just kept fading in and out. The next alarm was a code “1201”. It is likely that additional errors would have forced Gene Kranz at mission control to order an abort.

A more detailed analysis can be found in the mission summary -https://www.hq.nasa.gov/alsj/a11/A11_MissionReport.pdf

[To make matters worse, Apollo 11’s lunar module was running off course by a faster than planned descent, so the lunar module overshot the landing site by 4 miles into an area covered by boulders. Armstrong leveled off at 400 feet. According to astronaut Charlie Duke, monitoring events from Houston, “the LM was whizzing across the surface … It was far from what we had trained for and seen in the simulations. So I started getting a little nervous, and they weren't telling us what was wrong. It was just that they were flying this strange trajectory." In fact, they were dangerously close to running out of fuel and literally flying for their lives.] There is a more detailed account available online written by Rod Pyle - Apollo 11's Scariest Moments: Perils of the 1st Manned Moon Landing

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You can’t hear it in Armstrong’s voice but he was flying the craft manually to find a less hazardous alternative site and came within seconds of exhausting the module’s fuel and crashing. After an accident that far away there would be no AAA tow truck or rescue attempt. Armstrong’s announcement "Houston, Tranquility Base here. The Eagle has landed." allowed mission control to breathe a collective sigh of relief. Audio recordings and transcripts are available on NASA’s website, Apollo 11 Onboard Audio

Initially, the door would not open because the internal atmosphere would not completely vent. There was a danger that forcing the door would rupture it beyond the astronaut's ability to re-establish a seal. While exiting the craft for the first time Neil’s bulky suit broke off the ascent arming switch to leave the moon. Buzz Aldrin revealed how a pen saved him and Armstrong from a lonely death stranded on the moon.

When someone asked me why the Omega watch Armstrong was wearing was not technically the first watch on the moon it is because he had to leave it in the module when the onboard electric timer failed.

When the two astronauts were finally able to see their home: a distant blue marble, the weight of this accomplishment came down on their shoulders as the representatives of all mankind. They were standing on the Earth’s only natural satellite which had been orbiting the earth long before the dawn of civilization. There was the awe and mystery of being on an alien world and the realization of how small and frail man is compared to the cosmos.

Everybody thinks they know about the Apollo missions, but never stop to think just how complicated those 6 trips to the moon actually were. Men and women involved with the program worked within the limitations of 1960′s technology. The Apollo program was a huge success in the face of adversity and imminent danger. Someone had to be the first. America‘s cadre of astronauts were truly exceptional individuals. Sadly, no humans have been back to the moon since the Apollo 17 mission in 1972.

I would like to thank the people like Doug Parker and others who corrected my abysmal spelling and basically proofread this entry. Just because it was written on a holiday is no excuse for sloppy writing. Thanks guys! To all of the people who have upvoted this post and took the trouble to comment, it is humbling. I am reminded that the astronauts elected not to have their names added to the mission patch so that all the men and women in the program could share in the symbolic nature of this effort.