The Red Planet
As we leave behind the blue marble of Earth, we next encounter a smaller rocky world that is totally barren. This is the fourth planet from the Sun, and it is a a bright orange-red world pockmarked with deep scars and enormous mountain peaks. Its red color is the result of millions of years of iron oxidation. This planet is rusty. It is capped on both ends by bright sheets of white ice, and is accompanied by two tiny, lonesome, oddly-shaped bodies. This is the planet Mars, and its two moons, Phobos and Deimos.
Two TIny Moons
Mars is the last of the four terrestrial inner planets of the Solar System. It is about half the size of Earth and much less dense. Its red-orange color is caused by iron oxide, commonly known as rust. The Martian system contains two tiny moons named Phobos and Deimos. They were discovered in 1877 by Asaph Hall. These little moons look more like asteroids, and most astronomers believe that they may have actually been asteroids that were captured by the gravity of Mars. Both moons orbit very close to the planet. Phobos orbits so close, in fact, that its orbit is slowly decaying. Is it moving closer to the planet each year and will one day eventually crash into the surface.
Past Life
Because scientists believe that liquid water may have once existed on the surface of Mars, it is possible that life may have once existed there as well. Recent missions to the red planet have confirmed that water once flowed across the planet. It is also believed that the atmosphere of Mars was once much thicker than it is today. It is possible that some type of microscopic life forms may have existed on the planet during these ancient times. Many robotic spacecraft have attempted to verify evidence of past life on the planet, but so far this evidence has remained elusive. Future missions will examine the planet in more detail, but it may require a manned mission to the red planet to decide once and for all if life did or did not exist on Mars.
Exploring the Martian System
Because many scientists believe that life may have once existed on Mars, it has been explored more than any other body in the Solar System. A total of 38 missions have been launched to the Red planet, but due to various technical problems, only 19 of these missions succeeded. With a success rate of only 50%, many people have labeled this phenomenon as the Mars curse. Most of the failures occurred in the early years of the Russian Mars program. The United Statues has had better luck, with 13 of 18 missions succeeding in reaching Mars. But even this shows a success rate of only 72%. Fortunately, six out of seven attempts to land on the surface were successful.
The early missions to Mars consisted of a simply flyby of the planet. These missions collected data about the planet's magnetic field and atmospheric structure. The first close-up images of another world were sent from Mariner 4 in 1965. The low resolution images sent back from the spacecraft showed a barren world pockmarked with craters. There was no direct evidence of life and no sign of the famous canals that had been speculated by famous astronomer Percival Lowell. Later missions did, however, find what appeared to be dried stream beds, indicating that water may have once flowed across the surface of Mars at some time in the distant past.
The Viking mission was the first to land on the surface. On July 20, 1976, Viking 1 made a successful landing on Mars and captured the first images of the surface of an alien world. These images showed a barren, rocky terrain totally devoid of life. Later that year, on September 3, Viking 2 landed successfully and sent back similar images of the surface. Both landers took samples of the Martian soil to test for life. All tests were negative. It seemed Mars was a lifeless orb after all.
Since the Mariner and Viking missions, many other spacecraft have visited the Mars. Recent successes include the Mars Global Surveyor, Mars Pathfinder, Mars Odyssey Orbiter, the Phoenix lander, and the now famous Spirit and Opportunity rovers. These new missions have given us our most detailed views yet of the red planet. The Mars Reconnaissance Orbiter spent two years mapping and photographing the surface of the planet in detail. Spirit and Opportunity exceeded their intended life spans by several years and sent back conclusive evidence that liquid water once existed on the surface of Mars. They also revealed many unexpected phenomenon, such as large dust devils wandering across the surface of the planet.
Since the question of life still has not been answered conclusively, many future missions to Mars have been planned. The Mars Science Laboratory will be launched in 2011. This roving vehicle will be larger than Spirit and Opportunity and will perform much more advanced experiments. It will be five times heavier and carry ten times the number of experiments as its predecessors in an attempt to finally determine if live ever existed on the red plant.
It is quite possible that the question of life may only be answered by a manned mission to the Mars. Human beings may be able to find evidence that remains hidden to the robotic spacecraft. NASA plans to send people to Mars eventually, but the high cost and technical challenges may delay such a mission for many more years or even decades.