A date for the ages

Posted by Rich Talcott
on Friday, July 20, 2007
The first photo ever taken from the surface of Mars showed lots of
rocks and sand — and the footpad of the Viking 1 lander. NASA/JPL

Virtually everyone who reads this blog knows what happened on this date in history. But I'm not going to spend much time talking about Neil Armstrong's and Buzz Aldrin's small steps. Instead, I want to recall a lesser leap in human history, one that launched our search for life elsewhere in the universe.

On July 20, 1976, the Viking 1 lander touched down on Mars. That wasn't the original idea. When Viking 1 launched August 20, 1975, NASA planned to set the spacecraft down July 4 — the 200th anniversary of yet another significant historical date. But it was not to be.

The Viking spacecraft consisted of two joined parts: an orbiter and a lander. When the pair arrived at Mars June 19, the orbiter's camera started imaging the proposed landing site in Chryse Planitia. The pictures revealed a surface pocked with craters and far rougher than scientists expected. Mission planners decided they needed more time to find a better landing spot.

A few weeks of high-resolution Viking images combined with radar observations from Earth revealed a smooth area at the western edge of Chryse. NASA decided to head there and, on July 20, the lander separated from the orbiter and softly touched down on the surface. Just 25 seconds later, the first picture from the martian surface was on its way back to Earth. The rocky surface it revealed justified NASA's caution.

The main purpose of the Viking landers (Viking 1's sister ship, Viking 2, landed in Utopia Planitia September 3, 1976) was to search for martian life. They succeeded in only confusing the issue. The landers found strong evidence life exists — and compelling evidence that it does not. The ambiguous results mean Mars may still be the best place to search for extraterrestrial life, and NASA plans to continue this quest. With ever-more-sophisticated probes heading to the Red Planet, perhaps we'll know the answer before another decade of July 20 anniversaries passes by.

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