Following the Viking missions of the mid-1970's, which turned up a wealth of possibilities but no evidence for life, interest in the search for life did not decline but instead heightened, for the two landers deployed by Vikings 1 and 2 had proven that direct contact with the Martian surface was possible.
Scientists wanted to try new ideas, explore new possibilities. We desperately wanted to find the perfect way to explore another planet without sending humans. Two plans included a rover and a penetrator.
A rover would land on one spot and travel around searching for life in more than one location. It would be controlled by remote from Earth. NASA had dreams of a rover that could travel hundreds of miles from the landing site. Could this be done? Was this technology possible?
The Soviets already had experience using roving vehicles. They landed eight-wheeled Lunakhods on the Moon. Because the Moon is only 240,000 miles away, the operator on Earth only experienced a 2.6 second communications delay. This is not ideal for a mission to Mars. Mars is much farther away than the Moon. The two way communication time could be as much as 40 minutes. If a rover were headed over a cliff, nothing could be done to save it for nearly twenty minutes. By then, the little rover would have plummeted to its mechanical death.
Photo. The Sojourner rover, its name meaning a wanderer and recalling the legacy of black abolitionist Sojourner Truth, was deployed by the Mars Pathfinder probe, which landed on the Fourth of July, 1997. Measuring just two feet long by one and a half wide and one tall and weighing under 25 pounds, the Sojourner--shown here being inspected by Jet Propulsion Laboratory technicians--can move one foot in about thirty seconds; an advantage of having a rover like this one is in its ability to move to its scientific targets, primarily rocks. Courtesy of NASA.
Is there a better alternative? Another idea was to drop several torpedo-like devices into the Martian soil. They would penetrate the surface and travel deeper into the planet's soil. They would then transmit information to be analyzed in a laboratory here on Earth.
Photo. A penetrator like the one diagramed here from the Russian Mars 96 probe would travel perhaps 15 feet into the surface of Mars with on-board instruments like spectrometers, which would analyze the chemical composition of the soil. The penetrator itself (with separation point marked by the arrow) would dig into the ground while the top unit remained above the surface Courtesy of Malin Space Science Systems.
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