Mountain-sized comet to pass close to Mars

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HOUSTON, Tx. -- All eyes are on the sky, well at least NASA is checking it out. On Sunday, October 19,  a comet the size of a mountain is expected to come within 87,000 miles of Mars, not Earth. Still, by space standards, that's pretty darn close. So NASA's getting ready with five robotic explorers to try and snap some pictures of it.

NASA was able to capture pictures of a strange sighting on Mars, a strange cross like figure within a circle. The images were captured by the Mars Opportunity Rover. Some think the mark was made by one of the rovers' tires. Others think it's something else. Experts say a cross in a circle is sometimes called the Bolgar Cross or Sun Cross. It has a symbolic meaning, representing the four parts of a person: heart, mind, body and soul.

So is the mark from a Mars rover, or are aliens pulling a fast one on us?