The Viking Carbon Assimilation Experiments: Interim Report

Horowitz, N. H.; Hobby, George L.; Hubbard, J. S.

doi:10.1126/science.194.4271.1321

Cited by 46 publications

(18 citation statements)

References 4 publications

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“…Heating of both samples from 200° to 350°C and then to 500°C evolved comparable amounts of water in each step. The Biology Pyrolytic Release results for a sample collected beneath rock 7 (Figure I b) are also compatible with relatively large amounts of water [Horowitz et al, 1976]. Larger amounts of water should be expected in samples of soil collected from beneath rocks than in samples of soil exposed to the sun.…”

Section: Samples Under Rocks Vl-2supporting

confidence: 63%

“…The large amounts of water (for Mars) evolved during heating as part of the Molecular Analysis experiment lend strong support to models requiring storage of water in the Martian regolith [Fana/e, 1976;Huguenin, 1976). Water evolved from the sample under rock 3 at the VL-2 site during heating from 50° to 200°C may represent adsorbed water.…”

Section: Volatilesmentioning

confidence: 99%

“…The rock cap inhibits evaporation. Additionally, ultraviolet radiation causes dehydration of exposed soils [Huguenin, 1976].…”

Section: Samples Under Rocks Vl-2mentioning

confidence: 99%

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Surface materials of the Viking landing sites

Moore¹,

Hutton²,

Scott³

et al. 1977

J. Geophys. Res.

126

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Martian surface materials viewed by the two Viking landers (VL-1 and VL-2) range from fine-grained nearly cohesionless soils to rocks. Footpad 2 of VL-1, which landed at 2.30 m/s, penetrated 16.5 cm into very fine grained dunelike drift material; footpad 3 rests on a n:icky soil which it penetrated "'3.6 cm. Further penetration by footpad 2 may have been arrested by a hard substrate. Penetration by footpad 3 is less than would be expected for a typical lunar regolith. During landing, retroengine exhausts eroded the surface and propelled grains and rocks which produced craters on impact with the surface. Trenches excavated in drift material by the sampler have steep walls with up to 6 cm of relief. Incipient failure of the walls and failures at the end of the trenches are compatible with a cohesion near 10-10 2 N/m 2 • Trenching in rocky soil excavated clods and possibly rocks. In two of five samples, commanded sampler extensions were not achieved, a situation indicating that buried rocks or local areas with large cohesions (~ 10 kN/m 2 ) or both are present. Footpad 2 ofVL-2, which landed at a velocity between 1.95 and 2.34 m/s, is partly on a rock, and footpad 3 appears to have struck one; penetration and leg strokes are small. Retroengine exhausts produced more erosion than occurred for VL-1 owing to increased thrust levels just before touchdown. Deformations of the soil by sampler extensions range from doming of the surface without visible fracturing to doming accompanied by fracturing and the production of angular clods. Although rocks larger than 3.0 cm are abundant at VL-1 and VL-2, repeated attempts to collect rocks 0.2-1.2 cm across imbedded in soil indicate that rocks in this size range are scarce. There is no evidence that the surface sampler of VL-2, while it was pushing and nudging rocks "'25 cm across, spalled, chipped, or fractured the rocks. Preliminary analyses of surface sampler motor currents ("'25 N force resolution) during normal sampling are consistent with cohesion less frictional soils (c/J "' 36°) or weakly cohesive frictionless soils (C < 2 kN/m 2 ). The soil of Mars has both cohesion and friction.

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Section: Samples Under Rocks Vl-2supporting

confidence: 63%

Section: Volatilesmentioning

confidence: 99%

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Surface materials of the Viking landing sites

Moore¹,

Hutton²,

Scott³

et al. 1977

J. Geophys. Res.

126

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“…Preliminary accounts of the data returned from Mars have been published [Klein et al, 1976;Horowitz et al, 1976]. In this paper we summarize all of the data, including the results of two new experiments on Mars, and we conclude that they are unlikely to have a biological explanation.…”

Section: Introductionmentioning

confidence: 96%

Viking on Mars: The carbon assimilation experiments

1977

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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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“…In the fine material on the surface of Mars, the most abundant elements are silicon and iron, with concentrations of 45±5 wt % Si02 and 19±3 wt % Fe203 (14). The "Labeled Release" experiments carried out during the Viking Lander tests indicated some carbon assimilation of 14C-C02 (15). Laboratory simulation of these experiments were achieved using ferric iron saturated clays (16).…”

mentioning

confidence: 98%