The green alga Nannochloropsis sp. QII was cultivated in media with sufficient and growth‐limiting levels of nitrogen (nitrate). Nitrogen deficiency promoted lipid synthesis yielding cells with lipids comprising 55% of the biomass. The major lipids were triacylglycerols (79%), polar lipids (9%) and hydrocarbons (2.5%). The polar lipids consisted of a broad range of phospholipids, glycolipids and sulfolipids. Other lipids identified were pigments, free fatty acids, saponifiable and unsaponifiable sterol derivatives, various glycerides, a family of alkyl‐1, 4‐dioxane derivatives and a series of alkyl‐ and hydroxyalkyl‐dimethyl‐acetals. Experiments in which 14CO2 was provided at different times in the growth cycle demonstrated that enhanced lipid biosynthesis at low nitrogen levels resulted principally from de novo CO2 fixation.

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Three different types of biological experiments on samples of martian surface material ("soil") were conducted inside the Viking lander. In the carbon assimilation or pyrolytic release experiment, (14)CO(2) and (14)CO were exposed to soil in the presence of light. A small amount of gas was found to be converted into organic material. Heat treatment of a duplicate sample prevented such conversion. In the gas exchange experiment, soil was first humidified (exposed to water vapor) for 6 sols and then wet with a complex aqueous solution of metabolites. The gas above the soil was monitored by gas chromatography. A substantial amount of O(2) was detected in the first chromatogram taken 2.8 hours after humidification. Subsequent analyses revealed that significant increases in CO(2) and only small changes in N(2) had also occurred. In the labeled release experiment, soil was moistened with a solution containing several (14)C-labeled organic compounds. A substantial evolution of radioactive gas was registered but did not occur with a duplicate heat-treated sample. Alternative chemical and biological interpretations are possible for these preliminary data. The experiments are still in process, and these results so far do not allow a decision regarding the existence of life on the plonet Mars.

A fixation of atmospheric carbon, presumably into organic form, occurs in Martian surface material under conditions approximating the actual Martian ones. The reaction showed the following characteristics: The amount of carbon fixed is small by terrestrial standards; highest yields were observed in the light, but some dark activity was also detected; and heating the surface material to 90°C for nearly 2 hours had no effect on the reaction, but heating to 175°C for 3 hours reduced it by nearly 90%. New data from Mars do not support an earlier suggestion that the reaction is inhibited by traces of water. There is evidence of considerable heterogeneity among different samples, but different aliquots from the same sample are remarkably uniform in their carbon‐fixing capacity. In view of its thermostability it is unlikely that the reaction is biological.

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The major photoproduct obtained on irradiation of gaseous NH3 and CO mixtures is ammonium cyanate; lesser amounts of urea, biurea, biuret semi-carbazide, formamide and cyanide were observed. The formation of the major gas phase photolysis product may be rationalized by the following reaction sequence: (see article). Urea is probably formed from NH4NCO in a thermal reaction while formamide may result from the disproportionation of NH2CO. Photocatalytic syntheses of 14C-urea, -formamide, and -formadehyde are effected by irradiation of 14CO and NH3 in the presence of Vycor, silica gel, or volcanic ash shale surfaces. These syntheses are catalyzed by ultraviolet wavelengths longer than those absorbed by the gaseous reactants. The syntheses are also effected when the surface material is first irradiated in the presence of CO followed by a dark incubation with NH3. Apparently, the initiating step is a light dependent formation of a reactive form of CO on the surface. A discussion is given on the possible contribution of these reactions to the abiotic synthesis of organic nitrogen compounds on Mars, on the primitive Earth and in interstellar space.

Current ideas regarding the abiogenic synthesis of organic compounds on the planets rest on the theories of Oparin (1) and Urey (2), and on the experiments of Miller (3) and others, showing that the synthesis of biologically important compounds on the primitive earth was favored by the chemically reducing character of the primitive atmosphere. The importance of an excess of a reduced gas such as hydrogen, methane, or ammonia in laboratory simulations of these processes has often been pointed out (4). In view of these findings, it appears a priori unlikely that a synthesis of organic matter would be demonstrable in a gas mixture compositionally similar to the oxidized atmosphere of Mars. This atmosphere consists almost entirely of CO2 (5) with 0.1-0.3% CO (5, 6) and a small, seasonally variable quantity of water (7). Small amounts of other gases are not excluded. The mean surface pressure is about 6.5 mb (8). Solar ultraviolet (UV) reaching the surface is filtered through the CO2, which effectively absorbs wavelengths shorter than 1950 A. Thus, little energy is available at the surface for the activation of C02, CO, or water.We have performed organic synthesis experiments with mixtures of C02, CO, and H20 exposed to UV in the presence of soil or powdered vycor glass. The purpose of these tests was to uncover possible sources of error in an experiment, planned for the first Mars lander, designed to detect biosynthesis of organic matter in Martian soil (9). The The reservoirs were then brought to a total pressure of 1 atm by filling with diluent gas and with about 50 ml of liquid water previously flushed with the diluent gas. The [14C]CO reservoirs were attached to a pyrex manifold which had five positions for attachment of sample chambers. The latter consisted of quartz tubes (1.3 X 8 cm) with a detachable pyrex section containing a stopcock. Each chamber had a gas volume of about 5.5 ml. The chambers were evacuated and flushed with diluent gas, then filled manometrically to 1 atm with ['4C]CO and diluent gases. The pressure in the reservoir was maintained at 1 atm by adding water flushed with diluent gas.The vacuum system contained a liquid nitrogen trap to prevent diffusion of impurities from the mechanical vacuum pump. The vacuum indicator was a Wallace and Tiernan Gage. The gas reservoirs, manifold, and sample chambers were constructed of new glass that presumably had never been exposed to mercury. Also, all glassware was cleaned with 8 N HNO3 to minimize adventitious mercury contamination.The organic soil was an arable, fertile, brown soil with particle size less than 1 mm. Before exposure to [14C]CO, the soil was sterilized overnight in an oven at 1750C and then equilibrated for 1 hr at 100% relative humidity at 23°C.The vycor substratum was 80-100 mesh, highly fractured particles with a surface area of 173 m2/g. Before use, the vycor was heated to 7200C in air and equilibrated with water vapor as described above.Sample chambers containing gas mixtures were irradiated in a horizontal position with the soil...