No matter how well you plan for something, or how prepared you think you are, it is always possible for things to go wrong because of simple human error. We are not infallible as a race, and sometimes even the smallest mistake can have major repercussions on any given situation. Here are eight instances where simple human error has played a major role in the development of history as we know it.

1. NASA spacecraft crashes on Mars

In 1999, a NASA spacecraft, the Mars Climate Orbiter crash landed on the surface of the red planet. On September 23, 1999 the Mars Climate Orbiter was supposed to situate itself in orbit around the planet, but when the orbiter was making its final adjustments, NASA lost contact with the craft. It turns out that a programming error was to blame. One team had used metric measurements, while another had used imperial which caused the craft to crash. It ended up costing NASA $125 million and an untold amount of scientific data.

2. Joseph Stalin died because his guards were under orders.

Stalin was a brutal dictator of Soviet Russia, and because he was so feared his guards followed his orders without question. It was this loyalty that eventually led to the leader's death. Stalin ended up suffering a massive stroke, but because his guards were under orders not to disturb him for any reason, they were too scared to actually enter the room to help.  

3. One missing key could have saved the Titanic.

We all know the story of how the Titanic struck an iceberg in the Atlantic Ocean before sinking during its maiden voyage. It turns out that the whole fiasco could have been avoided if the crew had been given access to all of their tools. The iceberg likely would have been spotted in enough time if the crew had been looking through their binoculars, but those spectacles were locked in a cabinet that no one seemed to have a key for.  

4. Russia sells the U.S. the state of Alaska.

In 1867, the Russian government sold what they thought was a useless land mass to the United States for a whopping $7.2 million. They assumed that the land was good for nothing, but little did they know that Alaska would end up being exceedingly rich in oil and other minerals. Quite the steal for the Americans.

5. A misread speech led to the fall of the Berlin Wall.

In 1989, an East German politician gave a speech that was supposed to announce some very minor changes to the travel code, at least that was what was supposed to happen. What actually happened was that the politician accidentally implied that all travel restrictions were off, allowing people to come and go as they please. The rest is of course history.

6. The invasion of Cuba and the forgotten time zone.

The 1961 invasion of Cuba failed because of one of the most spectacular human error blunders imaginable. While planning out the invasion, the Pentagon had actually forgotten to consider the time zone change while planning out their attack. This screw up caused the fighter jets to show up an hour late which left all of the rebel forces unprotected.

7. German commander took the day off before the Allies landed at Normandy.

When the Allied forces landed at Normandy during the D-day invasion, the German commander in the area had actually taken the day off in order to celebrate his wife's birthday. While he was off spending time with his wife, the Allied forces captured the French coast, the coast that he was supposed to be defending from this very attack. We're pretty happy that the commander screwed the pooch on this one.

8. A bad translation sparked our belief in Martians.

The devil is in the details, and when it comes to translating other languages you must be very careful about how you go about it because it can unforeseen consequences. In 1877, the trenches visible on Mars were described as 'canali' (channels in English) by an Italian astronomer. An American astronomer later thought that this meant "man-made" channels, making him believe that there was intelligent life residing on Mars. This belief has spared a generation of conspiracies and investigations into whether we are alone in the universe.

What is the biggest 'human error' that you ever made? Were you able to fix it? Let us know in the comments.