Thursday, April 24, 2008

Viking biology

Hoagland & Bara appear to be confused about Viking biology. For those interested, here is a digest of the actual facts:

Both the Viking spacecraft landers had identical biology experiments. Each spacecraft carried three separate experiments designed to test for biology in Martian topsoil. The experiments were developed independently by three different Principal Investigators (PIs). The experiments were:

Gas Exchange (GEX) PI Vance Oyama, NASA Ames
Labeled Release (LR) PI Gilbert Levín, Biospherics, Inc.
Pyrolytic Release (PR) PI Norman Horowitz, CalTech

In addition, a Gas Chromatograph Mass Spectrometer (PI Klaus Biemann, MIT) supported the main biology package by testing for organic molecules.

Results: At both landing sites the results were essentially identical. GEX and PR were unequivocally negative. LR initially showed strongly positive results, with the control (a sterilized sample) showing negative as expected. Subsequent nutrient injections, however, showed no response. The GCMS detected no organic molecules.

Interpretation: Responsibility for interpreting this enigma fell on the Head of Viking Biology, Harold Klein, with support from Viking Chief Scientist Gerry Soffen. Both were NASA employees. Their call was thumbs down for Martian biology. From a scientific point of view, looking at the overall picture, an absolutely correct call -- but the LR results begged for an explanation. The hypothesis that was developed involved a chemical, not biological, reaction involving superoxides in the soil.

Dr Levín has been protesting this interpretation for more than 40 years. His main point is that the LR experiment detected life as pre-defined by agreed criteria during mission design. He has developed quite persuasive explanations for why the two other experiments and the GCMS gave negative results. Read more about his efforts in this article from

Hoagland & Bara seem aware that this is a controversy but they get it wrong. They maintain that there was a deliberate campaign within NASA to conceal Levín's data. That allegation is categorically untrue. Consider these points:

* The enigmatic results were extensively discussed with the media at the time by Klein and Soffen. A memoir of some of those discussions is here.
* No attempt whatsoever has ever been made to suppress publication by Dr Levín of his own interpretation. Mike Bara himself posted on the darkmission blog links to six of Levín's publications on the question.
* The complete LR data set, including the PI's notebook, is available to anyone on a NASA-sponsored web site.

Other comments by Hoagland & Bara suggest that they also think the consensus view is wrong — in other words, that they think Levín's experiment alone proves the existence of life on Mars. It's a contentious and highly technical issue, and considering that neither of them has any training in biology whatsoever, their views will certainly be ignored by anybody who matters.

No comments: