In the 1970s, NASA launched two spacecraft called Viking 1 and Viking 2 on missions to Mars. Both spacecraft photographed the surface of Mars and sent images back to NASA. In one photo, a hill on Mars' surface looked a little like a face. Author and conspiracy theorist ¬Richard Hoagland went a step further and said that it didn't just look like a face, it was definitely a face. Hoagland theorized that an alien civilization colonized Mars and that the face was evidence of an alien city in the Cydonia region. When other satellites photographed the surface of Mars, the pictures of the Cydonia region revealed that the face was just an eroded mesa. Hoagland argued that the equipment NASA used to take the subsequent photos wasn't as accurate as the Viking equipment. He also claimed that NASA doctored the images, making them look less like a face.

During the 1960s, the Soviet Union and United States raced to become the world leader in space exploration. The winner would be able to claim technological superiority over the other. The Soviet Union had the early edge: In 1957, it launched Sputnik, the first man-made satellite. In 1961, the Soviet Union dealt the American space program another blow when cosmonaut Yuri Gagarin became the first human in space. But, according to the Judica-Cordiglia brothers from Italy, Gagarin wasn't the first. The brothers set up a listening station in Italy to intercept communication transmissions between ground operations and spacecraft for both American and Soviet missions. Weeks before Gagarin's successful flight, the brothers claimed to have detected and recorded radio transmissions of a cosmonaut slowly dying while adrift in space. The Soviet Union denied the brothers' claim. Supporters of the theory believe the Soviet government hid the cosmonaut's death to preserve the country's prestige.

The granddaddy of all space conspiracy theories h as to be that themoon landings were faked on a soundstage. Those who believe the moon landings were hoaxes say that the U nited States lacked the technology necessary to transport humans to the moon and back. They claim that NASA faked the landings in order to make people believe the U.S. had fulfilled President John F. Kennedy's promise to land a man on the moon before 1970. NASA says that there's plenty of evidence that men landed on the moon. There are photos, videos and testimonials from the dozen astronauts who have set foot on the moon's surface. The astronauts returned with soil and rock samples, which NASA also cites as physical evidence of our presence on the moon. Some hardcore skeptics maintain that all of this evidence is fake or came from unmanned missions to the moon.

Does our solar system contain a giant, unnamed planet? It does, according to the Planet X theory. This theory says that our solar system has a 10th planet (but now officially 9th after Pluto was kicked out of the planet club). The planet is supposed to be enormous and on an orbital path that will bring it close to Earth soon. Proponents of this theory cite earthquake and weather data as evidence of this planet's growing influence on Earth. They also claim that the government is forcing observatories to close to keep the planet's approach secret and prevent panic. Several astronomers have said that there's no evidence for the Planet X theory, and that if the planet did exist, humans would be able to see it even without a telescope.

Supposedly, the Illuminati is a secret organization with ties to space. There are hundreds of different theories about the Illuminati, some of which say it's the organization to which all other secret governments report. In what is possibly the strangest theory on this list, some people claim that the Illuminati are the descendants of the union between humans and an extraterrestrial reptilian race. According to this theory, these hybrid descendents have infiltrated the highest levels of government in countries around the world. The supposed goals of the Illuminati range from simple world domination to preparing the Earth for extraterrestrial colonization. Skeptics say there's no evidence to support the existence of the Illuminati, but conspiracy theorists say that the lack of evidence actually proves the group exists. Believers say the Illuminati is so effective, they've erased almost all evidence of their existence.

We can blame it all on the Mayans. They created the Long Count Calendar, a time measurement system that had spiritual significance to their culture. They organized their calendar into several cycles, the last of which will end in December 2012. Some people think the Mayans had discovered that after 2012, the world would end. There are dozens of theories about how this might happen. Some claim that 2012 is when the Earth will experience a polar shift (see above). Others say that after 2012, the Earth will experience a period of terrible destruction followed by a new age of peace and enlightenment. A few claim that in 2012, a secret government will accomplish its goal of total world domination. What will actually happen? Check back with us on Jan. 1, 2013.

In 1956, Samuel Shelton founded a society that subscribed to a theory about the shape of the Earth -- namely, that it's flat. Shelton based his theory upon what he called common sense and personal observation. He called the scientific evidence for a globe-shaped Earth "dogmatic," meaning scientists were making this claim without adequate evidence. Later, when people showed him pictures of the Earth taken by satellites, Shelton claimed the photos were fake. He and the members of his society continued to support the idea that the Earth is flat and that those who disagree are part of a conspiracy to keep the truth about the Earth hidden. Shelton died in 1971, and leadership of the society passed to Charles Johnson. Johnson led the society until his death in 2001. Without leadership, the society fell apart.

On Dec. 14, 2006, Van denberg Air Force Base launched a rocket carrying a satellite called USA 193. The satellite was part of the National Reconnaissance Office's (NRO) intelligence program. In other words, it was a spy satellite. T he satellite had trouble maintaining orbit, and by late 2007 the Air Force determined that it would soon crash to Earth. The U.S. government announced in January 2008 that it intended to shoot the satellite down with a missile. Why shoot down the satellite? The government said it was because the satellite's fuel tank contained hydrazine, which is toxic. If the fuel tank survived re-entry, it could land on a populated area. On Feb. 20, 2008, the U.S. fired a missile and struck USA 193. Some people believe the government didn't tell the entire story. They say that the government also wanted to prevent the satellite from falling into another country's possession. Others go even further and suggest the United States just wanted to show off.

Some people believe that the Earth's North and South poles weren't always located where they are now. They believe the Earth once rotated on a different axis. Climate change, earthquakes and volcanic eruptions result from stresses on the Earth's crust. Some claim that the Earth will soon experience another dramatic polar shift, and that, as a result, entire continents might sink while new ones emerge from the sea. The polar shift hypothesis enters the worl d of conspiracy theories when some claim that top governments and scientists know of the impending shift but refuse to share the information with the public. Supposedly, they're keeping it a secret to avoid causing a panic. Skeptics dismiss polar shift hypotheses, saying that there's no real scientific basis for them. The Earth's true poles aren't the same as its magnetic poles, which are definitely shifting. The North Magnetic Pole is moving slowly northwest across the northern stretches of Canada.

No discussion about space conspiracy theories would be complete without mentio ning theRoswell incident. In July 1947, rancher Mac Brazel discovered some strange debris in an area northwest of Roswell, N.M. Brazel couldn't identify the debris, and a nearby military base released conflicting information about the material's origin. A few local newspapers picked up the story. While people thought the incident was unusual, several years passed before the first theories about alien activity really took off. At that time, dozens of UFO enthusiasts published stories and books about the Roswell incident. The basic theory was that the debris came from an alien spacecraft and that the United States government confiscated the material for later study.