Life on Mars?

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TIBS - August 1976

Life on Mars? Harold

P. Klein

Of all the planets in the solar system, Mars cal data, experiments to determine the appears to come closest to the Earth in elemental composition of the surface its chemical and physical environment [ 11, material, and analyses of the Martian although by terrestrial standards it is far atmosphere [4] will also go on. Three infrom hospitable. Accordingly, it is not sur- struments will bear directly on the quesprising that when plans were made in the tion of chemical evolution on Mars - the late 1960s for the first U.S. spacecraft to Viking lander cameras [5], a combined gas land on Mars, one of the major scientific chromatograph-mass spectrometer [6], objectives was an assessment of the and the Viking biology instrument [7]. organic evolutionary state of the planet, Contained in a volume of about 1 ft3 including a search for life. and weighing 351b the biological instruBarring unforeseen circumstances, two ment will receive up to four surface samunmanned spacecraft, making up the Vik- ples during each landed mission. These ing mission, will reach the planet this year, samples will be distributed within the inone on 19 June and the other on 7 August. strument t9 three different experiments After a few weeks when detailed close-up each of which makes different assumptions reconnoitering will take place, a lander will about the nature of any Martian detach from each spacecraft [2] and experiorganisms and the conditions under which ments begin in which Mars will be probed their metabolism might be demonstrated. directly for supportive evidence of modern The three experiments will establish differideas on the origin of life [3]. These studies ent incubation conditions by varying the will continue for about 60 days on each amount of water, the nature of nutrients spacecraft, with a number of analyses and the availability of simulated solar radiations. being made in each of several experiments. After sieving, particles of 2 mm and less In addition to seismic and meteorologi-

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from the upper 4 cm of the Martian surface will be delivered to the three biology experiments, to be incubated between 5 and 26” C. With each sample a portion will be held in reserve to serve as a control in the event that a presumptive positive result is obtained in any one experiment. For controls, the reserve sample will be heated at 160”C for 3 h prior to further analysis. One of the biological experiments, the Carbon Assimilation experiment [8], is designed to detect the assimilation of CO, or CO from the atmosphere into organic material. For this, the sample will be incubated in the presence of Martian atmosphere to which a small amount of 14C0 and 14C0, has been added. The experiment will first be conducted in light from a xenon-arc lamp with a spectral and energy distribution approximating that of the sun at the Martian surface. A small amount of water vapor will be included for the second incubation. After incubation for five days, the original radioactive atmosphere is removed and the sample is pyrolyzed to volatilize organic compounds. Radioactive organics obtained in this part of the experimental sequence would constitute a presumptive positive response. At the other extreme of assumptions, the Gas Exchange experiment will incubate Martian samples in the presence of

TIBS - August

N 176 a rich organic broth [9]. Samples of the incubation atmosphere will be analyzed periodically using a sensitive gas chromatograph optimized to measure H,, N,, O,, CH, and CO,; although other gases such as N,O and H,S are also detectable. Changes in the quantity of one or more of these gases over the course of a 19-day incubation will be evaluated for their possible biological significance. In a variation of this experiment, surface samples will be incubated without nutrients, but in the presence of water vapor. Atmospheric gas compositions will be measured using the same chromatograph-thermal conductivity detector system as described above. The third experiment will look for the release of CO, from simple organic substrates [lo]. For this, surface samples in the presence of Martian atmosphere will be incubated for 10 days with a very dilute solution of 14C-labeled formate, glycine, alanine, lactate and glycollate (uniformly labeled, D- and L-isomers where applicable), and the atmosphere above the samples monitored by a 14Cdetector to determine the kinetics of released gas following nutrient injection. The three experiments have been extensively tested using terrestrial soil samples and, as a result, it is safe to say that it is extremely unlikely that a false positive result will be obtained. On the other hand, the experiments appear to require significant numbers of terrestrial organisms to yield a response [ 11,121. Coupled with the cool temperature and the relatively short

incubation periods, the experiments may in fact yield false negative results. The Vikings clearly open a new chapter in biological experimentation. What is being attempted here is extraordinary in the history of biology: long-duration experiments, over a distance of over 200 million miles, entirely with automated equipment, and without the opportunity to deviate from experiment strategies that were conceived almost ten years ago ! References 1 Glasstone, S. (1968) The Book of Mars, NASA D.C. Special Publication,SP-I 79, Washington, 2 Corliss, W. R. (1974) The Viking Mission to Mars, NASA Special Publication, SP-334, Washington, D.C. 3 Horowitz, N. H. (1976) Account Chem. Res. 1-7 4 Soffen, G. A. and Young, A. T. (1972) Icarus 1-16 5 Mutch, T.A., Binder, A. B., Huck, F.O., Levinthal. E.C., Morris, E.C., Sagan, C. and Young, A. T. (1972) Icarus 92-110 6 Anderson, D. M., Biemann, K., Orgel, L. E., Oro, J., Owen, T., Shulman, G.P., Toulmin, P. and Urey, H.C. (1972) Icarus 11 I-138 7 Klein, H. P. (1974) Origins of Life 431-441 8 Horowitz, N. H., Hubbard, J. S. and Hobby, G. L. (1972) Icarus 147-152 9 Oyama, V.I. (1972) Icarus 167-184 IO Levin, G.V. (1972) Icarus 153-166 11 DeVincenzi, D. L. and Deal, P. H. (1976) NASA Technical Report No. R-460 12 Detailed test data are contained in reports MMC 1124 and MMC 1141, available from TRW Systems Group, Redondo Beach, California

Harold P. Klein is Director ojLifeSciences at NASA’s Ames Research Center in Mountain View, California, U.S.A.

The beginnings of the international congresses Fight for independence Hans A. Krebs In the early days biochemistry was regarded as a branch of physiology, and for the purposes of international contacts biochemists regularly participated in the International Physiological Congresses. Since 1889 these took place at three-yearly intervals. The International Physiological Congresses at Stockholm (1926), Boston, Mass. (1929), Rome (1932), Leningrad and Moscow (1935) and Ziirich (1938) were milestones in the history of biochemistry, for in those days other kinds of international meetings were rare. International symposia in specialized fields, frequent

today, were very exceptional events. Perhaps the first of the specialized intemational symposia in the area of biochemistry were those on ‘Quantitative Biology’ held annually at Cold Spring Harbor which began in ,1933. After the break due to the Second World War I learned by chance in the early summer of 1946 that the British Physiological Society intended to organize an intemational physiological congress at Oxford in 1947. At that time I was a member of the Committee of the Biochemical Society. The Minute Book of the Society includes the following entry for the meeting on 20 June 1946: ‘Professor Krebs enquired if the Secretaries had received any preliminary notification ofthe meeting of the International Physiological Congress to be held in Oxford in 1947. On receiving a reply in the negative he asked that the Secre-

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taries approach the organizers to ensure that biochemistry is allocated a share of the programme.’ The record of the next meeting, held on 27 September 1946, states: ‘The Secretaries read out a reply from the Secretary of the Physiological Society stating that owing to the limited accommodation available for visitors to the Congress he felt that it would be impossible to extend the general invitation to biochemists to participate in the Congress. He added that while no actual embargo would be placed on biochemical papers they would have to come from, and introduced by, members of the Physiological Society. Professor Krebs’ view was that this was a most unsatisfactory reply. This was unanimously supported and several speakers voiced the opinion that the time had come to take steps to promote an International Biochemical Congress. It was agreed that the Secretaries contact sister organizations, including the American Society of Biological Chemists and Joseph Needham (who at that time was Director of the Department of Natural Sciences at UNESCO, Paris), to obtain views on the question.’ On 2 November 1946 the Minute Book of the Committee of the Biochemical Society recorded: ‘The Secretary read a further letter from the Secretary of the Physiological Society that his Committee had confirmed the view expressed in his previous letter and that if the Biochemical Society decided to initiate congresses of their own, they had the Physiological Society’s blessing and encouragement, and offer of assistance.’ At a Committee Meeting on 31 July 1947 J. N. Davidson (Secretary) reported that during a recent visit to the United States he had consulted American biochemists who expressed a strong feeling that an international congress should be held in Europe in 1949. Encouraging comments had also been received from European sister societies and the specific suggestions had been made that the British Biochemical Society should go ahead and make the preparations for the organization of an international congress. The Committee then asked Davidson and F. Dickens to pursue the matter and on 31 October 1947 the Committee finally decided to go ahead with the preparations for the congress. A sub-committee was appointed consisting of Davidson, Dickens, Raistrick (Chairman) and Ernest Baldwin of Cambridge. The last-named was included because it was hoped that the meeting would be held in Cambridge in August 1949. Subsequently the Secretaries had full discussions with European biochemical