Viking: The Search for Life

Viking: the
Search for Life

In 1976 the Viking 1 and 2 landers undertook searches on the Martian surface for the chemical evidence of present or past life on Mars. The images shown below give a picture of one of the backup landers, and two different views of the Martian surface as photographed from Viking 1.

Viking lander (Ref) and two views of the Martian surface from Viking 1 (Ref)

In addition to photgraphing the surface, the Viking landers undertook a series of experiments at two points on the surface to find evidence for life.
The Experiments
The 4 basic experiments that the Vikings carried out to search for evidence of life were:

Gas Metabolism: look for changes in the atmosphere consistent with metabolism in the Martian soil.
Labeled Release: Look for release of radioactive carbon dioxide consistent with metabolism from organic material labeled by radioactive carbon.
Pyrolytic Release: Search for radioactive compounds in soil by heating soil exposed to radioactive carbon dioxide.
Mass Spectrometer: Search directly in Martian soil for organic compounds known to be essential to Earth life.
These experiments were built around the hypothesis that if there were life on Mars it would have a similar metabolism to life on Earth, and that it would have a similar biochemistry based on the same organic compounds important to life on Earth.
The Results
The results of these experiments were complex. The first three gave positive results, but the complete absence of any organic compounds in the Martian soil according to the mass spectrometer experiment suggests that the positive results for the first three were not evidence for life, but rather evidence for a complex inorganic chemistry in the Martian soil. Thus, the Viking verdict was that there was no evidence for present or past life on Mars.

Renewed Interest in Martian Life
This issue has been given renewed impetus by the recent claim (see also this and this) that a meteorite found on the Earth was once part of Mars (because of detailed chemical composition), and that there may be evidence in this rock for past organic activity. However, this is a very open topic at the moment, since there potentially are other explanations of the meteorite's content. We will have to wait on further evidence to clarify this issue.
The Newest Martian Missions

Pathfinder which explored the Martian surface in 1997. The image to the left is from Pathfinder on Mars.

Mars Global Surveyor: arrived in Martian orbit September 12, 1997. Here is a summary of its trajectory from Earth to Mars.
Recently there were a number of failed missions to mars. this site has some info on the failed lander mission, with links to other pages on the subject. It is thought that the climate orbiter was incorrectly navigated because engineers combining two computer programs into one did not correctly convert the units from english to metric systems.
The failure of the Mars lander involved some design flaw or timing error such as the lander turning off its landing rockets too early, in part due to software mismatches where English units were used in one place and metric units in another. There were also perhaps some fundamental management problems with the Jet Propulsion Laboratory (JPL) in Pasadena (where the Mars lander was designed and built). This could have ultimately contributed to y mis-communication between the engineers and the managers, and the "goal" of getting the thing made cheap and fast may have played a role. NASA (which runs JPL) has made an effort to reduce costs and has put forth the slogan "Faster, Better, Cheaper" which could really be viewed as "Faster, Cheaper, Probably Worse." This is changing as NASA has now slowed development of the next lander.
Now (2004) however, although the British lander "Beagle" has also failed, NASA has successfully landed the surface rovers Opportunity and Spirit. Much more information about these new successful missions is updated continuously (March 2004) and can be found here: Mars Rovers (latest updates are here ).



Viking lander (Ref) and two views of the Martian surface from Viking 1 (Ref)