Biggest Mysteries of Mars
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Mars was known as the "fire star" to ancient Chinese astronomers, and scientists are still burning with questions regarding the Red Planet. Even after dozens of spacecraft have been sent to Mars, much remains unknown about that world. Here are some of the biggest unsolved mysteries we have about Mars.
Why does Mars have two faces?
Scientists have been puzzling over the differences between the two sides of Mars for decades. The northern hemisphere of the planet is smooth and low — it is among the flattest, smoothest places in the solar system, potentially created by water that once flowed across the Martian surface.
Meanwhile, the southern half of the Martian surface is rough and heavily cratered, and about 2.5 miles to 5 miles (4 km to 8 km) higher in elevation than the northern basin. Recent evidence suggests the vast disparity seen between the northern and southern halves of the planet was caused by a giant space rock smacking into Mars long ago.
Still, there are ways to produce methane without life, such as volcanic activity. ESA's ExoMars spacecraft planned for launch in 2016 will study the chemical composition of Mars' atmosphere to learn more about this methane.
Does liquid water run on the surface of Mars now?
Although large amounts of evidence suggest that liquid water once ran on the surface of Mars, it remains an open question as to whether or not it occasionally flows on the face of the Red Planet now. The planet's atmospheric pressure is too low, at about 1/100th of Earth's, for liquid water to last on the surface. However, dark, narrow lines seen on Martian slopes hint that saltwater could be running down them every spring.
Were there oceans on Mars?
Numerous missions to Mars have revealed a host of features on the Red Planet that suggest it was once warm enough for liquid water to run across its surface. These features include what appear to be vast oceans, valley networks, river deltas and minerals that required water to form.
Nevertheless, astronauts seem eager to find out. For example, this year six volunteers lived in a pretend spacecraft for nearly a year and a half in the so-called Mars500 project, the longest spaceflight simulation ever conducted, aimed at replicating a manned mission to Mars from beginning to end. There are even numerous volunteers for a one-way trip to the Red Planet. Tiny rock-eating microbes could mine precious extraterrestrial resources from Mars and pave the way for the first human colonists, and farmers could grow crops on its surface. The mystery as to whether or not humans will ever go to Mars may rest largely on whether or not the powers-that-be can be convinced to go there.