Saturday, July 20, is the 50th anniversary of the Apollo 11 space program’s landing on the moon. In honor of the achievement, Citizen Truth will run a series of articles about little known aspects of the Apollo 11 space program all week.

From rockets to remnants, here are the top five interesting Apollo moon landing facts you probably haven’t heard about, plus some bonus entries.

1. Fuel Scare

When Apollo 11 landed, the tank had only about 25 seconds of fuel remaining. That’s very stressful, and maybe it is why the Apollo 11 schedule called for Buzz Aldrin and Neil Armstrong to take a nap right after landing on the moon. However, the two naturally could not wait to get to the lunar surface to start exploring. They ditched the nap and instead made history. Once they got to the surface, they began taking pictures. Many have commented over the years that all the pictures seem to be of Aldrin. Armstrong was not only the pilot,but also the designated photographer, and as such, there are very few pictures of Armstrong on the moon.

2. Where are the American Flags?

It is well known that each Apollo crew left an American flag on the moon, but the source of the flags remains a mystery. One story NASA tells is that secretaries bought $5 flags at Sears during their lunch breaks. Because Neil Armstrong saw the Apollo 11 flag fall down when they lifted off from the lunar surface, scientists assumed the other flags fell too. However, a 2012 lunar orbiter took photos of the landing sites for Apollo 12, 16 and 17, and the flags were still standing. Likely, the flags were probably not in the best condition due to the continuous cosmic radiation, but they were nevertheless still standing. Not bad for a $5 flag from Sears.

3. Experiments Left Behind

The Apollo 11 astronauts also left experiments there for subsequent Apollo astronauts to check on. The Apollo spacecraft had very little extra room for astronauts to bring personal items on-board, but Armstrong brought remnants of an airplane that belonged to the Wright Brothers, who like Armstrong were from Ohio.

4. Moon Rocks Mistake

You have to be living under a rock to not know that the astronauts brought back moon rocks, but few know how many were brought back. In all, 46 pounds were returned and are still studied to this day. Many years later, NASA accidentally auctioned off the bag that carried the first lunar samples. The buyer paid $995 and sent the bag to NASA for verification. When NASA realized their mistake, the agency refused to return the bag to the purchaser.

5. An Alternative Insurance Plan

At the end of the day, Apollo 11 was incredibly dangerous—so dangerous that no insurance company would insure Collins, Armstrong and Aldrin, so the astronauts signed photos. They left these autographs with their families so that if they perished, the families could auction the photos for money.

Honorable Mentions

Rocket Engineering

Even though SpaceX’s current Falcon Heavy rocket is extremely powerful, it still pales in comparison to the Saturn V rocket that launched Apollo 11. The Saturn V stood 363 feet tall with a liftoff thrust of 7.6 million pounds. By comparison, Elon Musk’s Falcon Heavy is about 230 feet tall with a liftoff thrust of 5 million pounds. Amazon’s Jeff Bezos is also involved in private spaceflight with his company Blue Origin. Bezos’ team actually explored the Atlantic Ocean for remnants of Saturn V rockets and incredibly recovered parts of the Apollo 11 rocket.

Your Space Ready Cell Phone

Speaking of technology, the Apollo 11 on-board computers were state-of-the-art in 1969, but now your cell phone is more powerful. The Apollo computers became overloaded many times, and the crews had to perform several tasks manually because of it.