SP-425 The Martian Landscape

 

The Viking 1 Landing

 

[26] On June 19, 1976, Viking 1 successfully achieved orbit about Mars. There followed an exhausting month while pictures taken from orbit were analyzed and the search for a safe landing went on-and on. The landing had been planned originally for July 4, but the predesignated site was judged to be too hazardous. Alternate sites were identified, only to be revealed as equally hazardous when more pictures were acquired from orbit.

Marathon meetings served primarily to underline our ignorance regarding the actual hazards of any site. Two types of evidence, neither very persuasive, were considered. The pictures from orbit had best resolution on the order of 50 m, considerably greater than the size of objects that might effectively destroy the Lander. Radar signals from Earth, bounced off Mars and returned to Earth, were influenced by the roughness of the surface at the scale of a few centimeters, but the exact character of that influence was arguable. Perversely, all areas that were acceptably smooth in pictures appeared rough to radar, and vice versa. It seemed as if we were doomed to some sort of orbital purgatory.

Finally, the Project Manager was persuaded that an acceptably smooth site existed at 22°N, 48°W in Chryse Planitia, the Plains of Gold. The landing was scheduled for July 20. An answer to the unspoken question that had been in our minds for eight years was close at hand.

Thirty hours before Orbiter-Lander separation the two cameras were turned on for the first time in nine months, a rerun of the simulated event which had created such confusion a few weeks previously. This time everything worked perfectly. The numbers telemetered back to Earth and disgorged on stacks of computer printouts indicated that the cameras were operating just as we had anticipated. Strangely, as I looked at those pages of stark numbers, I felt the sort of joy that passes between friends long separated and once again united. Our companions, the cameras, were alive and well.

Separation occurred at 1:51 a.m., Pacific Daylight Time, July 20. Slowly at first, and then more rapidly, the flight path of the Lander branched from the Orbiter, bending down toward Mars. The final descent through 6.1 km took less than two min. At 5.9 km a parachute was deployed. Two sec later it was fully inflated. Seven sec later the aeroshell was ejected and the landing legs deployed. Fifty-one sec later the terminal descent engines ignited. Two sec later the parachute and base cover were separated. Forty-four sec later the Viking 1 Lander touched down on the surface of Mars.

It is not my intention to review here all the events and scientific results following that first landing. The camera results are best appreciated by leafing through the folio of pictures that makes up the major part of this volume. With the exception of the seismometer on Viking 1, all instruments on both Landers operated as expected. A wealth of information concerning the martian environment is now in hand.

Predictably, interest has focused on the results of the biology investigations. Since all three of the experiments designed to test metabolic activity of a microbiota yielded "positive" results, it is tempting to conclude that life exists on Mars. Indeed, some of the early meetings, in which preliminary biology results were reported, were charged with the excitement of profoundly important speculations about to become historical reality. We now recognize that the biology results can be explained by inorganic surface reactions in the absence of any living forms. Strengthening this conclusion is the absence of organic compounds, documented by a gas chromatograph mass spectrometer (GCMS) experiment. But surely this does not prove the absence of life on Mars, only its absence at two localities purposely chosen to be bland and featureless. It remains possible perhaps unlikely, although statistics in this instance have little validity-that life exists elsewhere on Mars in some special environmental niche-or that it existed millions of years ago.

 


 image of Steve Wall and Ken Jones

Figure 21. Steve Wall and Ken Jones (with the helmet) several hours after the successful landing of Viking 1. Wall and Jones were part of the FOVLIP team that reconstructed the first pictures as the data were radioed back from Mars. (Photograph by Richard E. D'Alli)


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