PerspectivePlanetary Science

Organic molecules on Mars

See allHide authors and affiliations

Science  08 Jun 2018:
Vol. 360, Issue 6393, pp. 1068-1069
DOI: 10.1126/science.aat2662

eLetters is an online forum for ongoing peer review. Submission of eLetters are open to all. eLetters are not edited, proofread, or indexed.  Please read our Terms of Service before submitting your own eLetter.

Compose eLetter

Plain text

  • Plain text
    No HTML tags allowed.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.
Author Information
First or given name, e.g. 'Peter'.
Your last, or family, name, e.g. 'MacMoody'.
Your email address, e.g.
Your role and/or occupation, e.g. 'Orthopedic Surgeon'.
Your organization or institution (if applicable), e.g. 'Royal Free Hospital'.
Statement of Competing Interests

This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.

Enter the characters shown in the image.

Vertical Tabs

  • RE: The Labeled Release (LR) experiments--Vikings I and II -- 1976
    • George Nickas, Emeritus Professor Physics and Astronomy, Hanover College, Hanover, IN

    You do not seem to be aware, or at least ignore the positive results for living organisms returned in situ from the Viking I and II landers in 1976 by the Labeled Release (LR) experiment.. This work has been summarized and published by the primary investigator, Dr, Gilbert Levin. Here is a recent summary from Professor Levin:

    Dr. George D. Nickas
    Corpus Christi, TX

    Competing Interests: None declared.
  • Newly discovered organic molecules on Mars and revisiting Viking’s LR experiment

    I would like to give my thanks to Inge Loes ten Kate for writing this excellent analysis named “Organic molecules on Mars” and I would also like to thank Science for publishing it. The author is correct when he says that the recent findings of Curiosity rover are “breakthroughs in astrobiology”. But I have some disagreements when he states the following concerning NASA’s 1976 Viking mission: “However, neither signs of life nor organic compounds were detected in the regolith samples analyzed during this mission”.
    Each of the two Viking Landers carried one Labeled Release (LR) Experiment, which tested the Martian soil for metabolic activity. The results from the experiment are ambiguous. So far the prevailing scientific consensus is that these results should rather be explained by non-biological sources, but not everyone agrees. I would like to remind that in the Science’s article published in 1976 by Gilbert V. Levin and Patricia Ann Straat, it was stated that regardless of the fact Viking’s GCMS couldn’t detect organic compounds, no chemical experiment has quantitatively reproduced the LR Mars data, which is a reason why biological activity should be considered (1). Decades later, in 2016 G.V. Levin and P. A. Straat published another article (2) in which they once again affirmed that a non-biological agent cannot satisfy all Viking findings, thus biology should be considered as an explanation.
    As a researcher I follow the principle that extraordinary claims req...

    Show More
    Competing Interests: None declared.