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35 Years since Viking 2
Although the human experience in space is an important part of the history and the future of the United States, robotic exploration is particularly useful in helping us understand the universe. For the present, robots have the capability of visiting places in our solar system where humans cannot and they can thus perform important research which humans cannot. Robotic spacecraft could only be the precursor to actual human exploration of the solar system, particularly Mars. The Viking program was one of NASA's earliest attempts at exploring Mars, next to the Mariner program, which ended in 1973. When the Viking 2 spacecraft launched in 1975, along with its twin Viking 1, it journeyed to Mars in search of knowledge and in search of life. Viking 2 made several significant discoveries, revolutionizing our understanding of Mars and spurring interest for further investigation--still today, scientists dream of the technological capability of sending humans to the Red Planet. Viking 2 was a very educational mission, in terms of what we discovered about our planetary neighbor and in terms of learning how to reach it. Accordingly, missions like the Viking 2 spacecraft, can bring us one phase closer to actually setting foot on Mars in the future.
Viking 2, a unique spacecraft destined for the Red Planet, consisted of an orbiter and a lander. The orbiter was 2.5 meters across, but, including the four solar panels around the spacecraft's axis, the craft stretched from tip to tip at 9.7 meters. The total height of the spacecraft was 3.3 meters. Without fuel, Viking 2 weighed 883 kilograms, or nearly a ton, while the lander itself weighed 576 kilograms. There were 1445 kilograms of fuel. The orbiter received 620 watts of power from its solar panels, while the lander received 70 watts of power from its radioisotope thermoelectric generators, which converted the heat from decaying plutonium-236 into electricity. The Viking 2 lander was controlled by a complex computer, which was, according to NASA, "one of the greatest technical challenges of Viking." The memory in this computer could provide the lander with instructions for the first 22 days on the planet, without any help from the earth. The lander was built to withstand temperatures of -184 Fahrenheit during the night, with a thin aluminum skin of .86 millimeters thick. In total, the Viking project cost approximately one billion dollars, but in terms of the information we gained from the spacecraft, it was well worth the money.
For example, the two Viking spacecraft determined that Mars's two moons, Phobos and Deimos, were of low density, signifying that they probably were once asteroids, captured by the planet's gravity. This helps us understand more about the way in which our solar system was formulated. More importantly, Viking 2 carried with it a package of three biology experiments because we were anxious to verify if life existed on a planet other than the earth. The investigation consisted of the pyrolitic release (PR), the labeled release (LR), and the gas exchange (GEX) experiments, which analyzed the composition of Martian soil samples. No organisms could be found surrounding the lander. However, scientists learned that it could have been possible for life to exist on Mars sometime in the past. Viking 2 discovered a large proportion of nitrogen in the atmosphere, which indicates that the conditions of Mars and its atmosphere were quite different in the past. Due to Mars's current lack of atmosphere, it is cold, dry, and bombarded with ultraviolet radiation, rendering the planet "self-sterilizing" and unable to support life. Even after Viking, the search for past or present life on Mars has intrigued NASA: we have continued to send robotic spacecraft, like the Mars Exploration Rovers and the Phoenix lander, to study the Martian surface.
Additionally, along with the debate about whether there is or has been life on Mars, comes the question: is there water on Mars? As the NASA History Division explains, "Late in the nineteenth century, interest was enormously heightened by reports of canals on the surface. This led to speculation that life might thrive there under climatic conditions similar to those on the Earth and that the canals might be the product of an advanced civilization." However, as we learned from Viking, the artificial canals are actually natural channels possibly formed by water, indicating that Mars used to have a different climate than it does now. Now, Viking 2 was different from Viking 1 in that it landed at a higher latitude, permitting close-range observations of Mars's polar region. This was important in that Viking 2 was able provide us with evidence that the polar cap consisted of water ice, not frozen carbon dioxide as was previously thought. Thus, we concluded, thanks to Viking 2, that liquid water most likely existed on Mars in the past, even though now there is only water ice.
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