Mars—an Unresortful Planet
from the book, "Petrified Lightning"
Mars—an Unresortful Planet
The planet Mars is unique in the solar system. Some planets are geologically inert, while others are so active that they obscure their own history; Mars displays geologic features from its birth to recent events. Moreover it is open, through its thin atmosphere, to scrutiny.
Many features of Mars make it a sister planet to Earth. Its day is only 371/2 minutes longer than an earth day, and the tilt of its axis, 23.98 degrees, differs less than one—half degree from Earth's 23.5 degrees. The polar ice caps of Mars grow and shrink, and its seasons appear to fluctuate as do those of Earth. Although Mars is only half the size of Earth, its year is 687 earth days, almost twice the length of our year.
The idea of life on Mars has persisted for many centuries. In 1879 the Italian astronomer Giovanni Schiaparelli discovered an extensive network of small, straight lines crisscrossing the planet. He called these canali, meaning "channels," but the name was easily corrupted in English to "canals," which implied waterways made by inhabitants of Mars. Astronomers were skeptical, but the idea gained tremendous popular appeal. In the late 1880s Percival Lowell built the Lowell Observatory in Flagstaff, Arizona, to get a better look at Mars and confirmed the "canals." The obvious conclusion was that, in a last—ditch effort to rescue their planet from its desperate water shortage, engineers had constructed a global canal system to transport water from the polar ice caps to equatorial deserts. Dark oases where the canals crossed further confirmed the findings until other astronomers, using Lowell's telescope, discovered the canals were optical illusions.
Belief in Martians dies hard; the War of the Worlds scare that accompanied Orson Welles's radio "newscast" in 1938 showed that Earthlings are all too willing to believe in alien life from the red planet. One U.S. vice president's argument in support of the Mars Observer space project was that, since scientists can clearly see water canals on Mars and canals are built by rational beings, Mars may possibly support fellow humans.
The Mariner probe in 1964 revealed the planet's true face as barren, heavily cratered, and bereft of breathable air or any of the green, purple, or tentacled creatures created in the many science fiction stories about the red planet. Moreover, scientists now know that Mars has no ozone layer to protect it from ultraviolet radiation; therefore its soil has been rendered completely sterile! The space probe Mars Observer, destined to orbit Mars in summer 1994, would have answered many of the questions asked about this planet. Unfortunately the mission was unsuccessful, and the craft is presently lost somewhere in outer space.
Successful missions have shown much of the spectacular landscape of Mars. The planet boasts a "Grand Canyon," Valles Marineris, over 2,500 miles long and more than 5 miles deep that dwarfs the Arizona tourist mecca. Enormous dust storms periodically obscure the planet's features, and shimmering polar caps of frozen carbon dioxide (dry ice) seasonally wax and wane during each Martian year.
Far more spectacular than its ice caps are Mars's breathtaking volcanoes, the largest in the entire solar system. Four gigantic volcanoes are located on a 3,500—mile equatorial blister called the Tharsis Bulge. The largest volcano, Olympus Mons, is 15 miles high and 360 miles across its base, with a caldera 54 miles in diameter. Scientists speculate that these gigantic mountains of fire, now dormant, may be potentially active.
With its towering 78,000—foot volcano (two and one—half times as high as Mount Everest) and its canyon over 20,000 feet deep, the Mars profile is about 100,000 feet. Even with our Marianas Trench 36,198 feet below sea level, Earth's profile is a mere 65,000 feet, just two—thirds that of Mars.
At present Mars cannot support surface water because it would either evaporate or freeze solid. Yet past probes have clearly indicated that water once existed on this planet of extremes. This does suggest that the Martian climate may have once been radically different from the present and may have resembled the climate of Earth. Probes in the 1960s and 1970s photographed branching valleys that looked exactly like dry riverbeds in our desert areas. In addition to the many small branching channels, there are signs that catastrophic floods scoured widespread areas from time to time. Violent eruptions of groundwater appear to have gouged huge channels up to 90 miles wide into the surface. The discharge rates of these raging floods were over a hundred times the rate of flow of the Mississippi River. These great floods seem to have occurred episodically through Mars's early history. The pictures were taken on the three—billion—year—old surface of its southern hemisphere. Almost inescapably, at some time the atmosphere was thicker and the climate was warmer. Perhaps this occurred when the rotational and orbital motions of the planet caused differences in the amount and distribution of solar energy. A few scientists speculate that at such times in its history Mars could have had oceans.
Few doubt that Mars contained much water in its geologic past, but where is it now? Some water has been detected in the atmosphere and some in the polar caps, but most appears to have vanished. Although some scientists suggest that the water might somehow have been blown off the planet, most believe it is still there, locked in ice under the surface or trapped in clay minerals.
However warm and humid the climate might have been in the past, it is far from that at present. By Earth's standards Mars is a forbidding place. Summer temperatures at noon over the equator could reach a pleasant 68 degrees Fahrenheit, but because the Martian atmosphere (consisting mostly of carbon dioxide) is so thin, the nighttime temperatures can plunge several hundred degrees. During a Mars winter the temperature at polar regions will hover at minus 220 degrees Fahrenheit. There will be no sunbathing there!