Editing Viking 2 (section)

===Landing site soil analysis===
The regolith, referred to often as "soil," resembled those produced from the weathering of basaltic [[lava]]s.  The tested soil contained abundant [[silicon]] and [[iron]], along with significant amounts of [[magnesium]], [[aluminum]], [[sulfur]], [[calcium]], and [[titanium]]. Trace elements, [[strontium]] and [[yttrium]], were detected.

The amount of [[potassium]] was one-fifth of the average for the Earth's crust. Some chemicals in the soil contained sulfur and [[chlorine]] that were like those remaining after the evaporation of seawater. Sulfur was more concentrated in the crust on top of the soil than in the bulk soil beneath.

The sulfur may be present as [[sulfate]]s of [[sodium]], magnesium, calcium, or iron. A [[sulfide]] of iron is also possible.<ref>Clark, B. et al.  1976.  Inorganic Analysis of Martian Samples at the Viking Landing Sites.  Science:  194. 1283–1288.</ref> The [[Spirit Rover|''Spirit'' rover]] and the [[Opportunity Rover|''Opportunity'' rover]] both found sulfates on Mars.<ref>[https://web.archive.org/web/20040626074013/http://marsrovers.nasa.gov/gallery/press/opportunity/20040625a.html Mars Exploration Rover Mission: Press Release Images: Opportunity<!-- Bot generated title -->]</ref>

Minerals typical weathering products of [[mafic]] [[igneous rocks]] were found.<ref>Baird, A.  et al.  1976.  [https://www.science.org/doi/abs/10.1126/science.194.4271.1288 Mineralogic and Petrologic Implications of Viking Geochemical Results From Mars: Interim Report.]  Science: 194. 1288–1293.</ref>  All samples heated in the [[Gas chromatography–mass spectrometry|gas chromatograph-mass spectrometer]] (GCMS) gave off water.

However, the way the samples were handled prohibited an exact measurement of the amount of water. But, it was around 1%.<ref>Arvidson, R et al.  1989.  The Martian surface as Imaged, Sampled, and Analyzed by the Viking Landers.  Reviews of Geophysics:27. 39-60.</ref> Studies with [[magnets]] aboard the landers indicated that the soil is between 3 and 7 percent magnetic materials by weight.  The magnetic chemicals could be [[magnetite]] and [[maghemite]], which could come from the weathering of [[basalt]] rock.<ref>Hargraves, R. et al. 1976.  Viking Magnetic Properties Investigation: Further Results. ''Science'': 194.  1303–1309.</ref><ref>Arvidson, R, A. Binder, and K. Jones.  The Surface of Mars. ''Scientific American''</ref>  Subsequent experiments carried out by the Mars ''Spirit'' rover (landed in 2004) suggest that magnetite could explain the magnetic nature of the dust and soil on Mars.<ref>Bertelsen, P. et al.  2004.  Magnetic Properties Experiments on the Mars Exploration rover ''Spirit'' at Gusev Crater.  ''Science'': 305. 827–829.</ref>
{{Wide image|Mars Viking 22a002.png|1500px|''Viking 2'' lander image of Utopia Planitia.}}