Mineral Composition: Sulfur Mineralogy

Mineral sulfur has several different allotropes. For cyclooctasulfur, the most common polymorph is ⍺-sulfur. Other forms are ꞵ-sulfur, which is only thermodynamically stable between 95-120 °C (typically found in volcanic or fumarolic environments), and the exceedingly rare 𝛾-sulfur (or rosickyite). Both of these forms are semistable and revert back to ⍺-sulfur at room temperature. However, there are some cases in which these forms appear anomalously that could indicate the presence and/or activity of microbial life. Some suggest that rosickyite and/or ꞵ-sulfur in these environments are the direct product of microbial activity. Others argue that they are instead due to the presence of organic carbon compounds (some of which can be produced abiotically), which stabilize these minerals. Differences in the occurrence and structure of sulfur minerals may be an indicator of biotic vs. abiotic production.

Created at: 
2022-09-27
Updated at: 
2024-08-15
Curator: 
Graham Lau
Authors: 
Graham Lau , Adriana Gomez-Buckley  
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Definition
HIGH
LOW

Rosickyite and ꞵ-sulfur found in non-volcanic/fumarolic locations are typically either direct products of microbial sulfur oxidation, or are due to the presence of biotically-produced organic carbon. [Congruence]

Environments
Mars: Surface, Mars: Subsurface, Ocean Worlds: Enceladus Surface, Ocean Worlds: Enceladus Subsurface, Ocean Worlds: Europa Surface, Ocean Worlds: Europa Subsurface
eStable rosickyite was found in samples from Borup Fiord Pass, a low-temperature glacial site, and was thought to be potentially biogenic in origin.

eThe presence of rosickyite in a microbial community in Death Valley suggests the activity of microorganisms is responsible for maintaining this mineral in stable form.

eStable rosickyite and ꞵ-sulfur found in the low-temperature setting of Borup Fiord Pass are likely due to the presence of complex organic matter/carbon.

eIn experiments reacting sulfide with complex dissolved organics (yeast extract, peptone), elemental sulfur (S(0)) was shown to organomineralize into various microstructures similar to those created directly by microbial activity.

eS(0) formation by chemolithoautotrophic sulfur-oxidizing bacteria S. kujiense produced rosickyite and ꞵ-sulfur, which formed and was stabilized due to the presence of organics secreted by the bacteria.

 

Magnetotactic bacteria produce greigite more quickly at ambient temperatures than in abiogenic analogue experiments. [Congruence]

Environments
Ocean Worlds: Enceladus Subsurface, Ocean Worlds: Europa Subsurface, Ocean Worlds: Titan Subsurface, Ocean Worlds: Other
eAbiogenic greigite formed in experiments where formaldehyde (HCHO) was added to iron sulfide (FeS) and hydrogen sulfide (H2S) was produced at a much slower rate than biogenic greigite in magnetotactic bacteria.

 
Definition
HIGH
LOW

Microbial influence on geochemical conditions allows rosickyite to form and remain stable in non-volcanic/fumarolic conditions. [Survivability]

Environments
Mars: Surface, Mars: Subsurface
eThe presence of rosickyite in a microbial community in Death Valley suggests the activity of microorganisms provide the appropriate geochemical conditions for it to remain stable.

 

ꞵ- and 𝜸-sulfur (rosickyite) allotropes are stable at low temperatures in the presence of complex organic carbon compounds. [Survivability]

Environments
Ocean Worlds: Enceladus Surface, Ocean Worlds: Enceladus Subsurface, Ocean Worlds: Europa Surface, Ocean Worlds: Europa Subsurface
eThe presence of organic matter from possible but unconfirmed microbial sources at Borup Fiord Pass allows the mineralization of rosickyite and ꞵ-sulfur.

eThe abundance of EPS (particularly polysaccharides and lipids) within Borup Fiord Pass sulfur deposits provide the necessary conditions for the formation of rosickyite.

 
Definition
HIGH
LOW

Rosickyite and ꞵ-sulfur found in non-volcanic/fumarolic conditions can be due to the presence of simple, abiotically-produced organic carbon compounds. [Congruence]

Environments
Mars: Surface, Mars: Subsurface, Ocean Worlds: Enceladus Surface, Ocean Worlds: Enceladus Subsurface, Ocean Worlds: Europa Surface, Ocean Worlds: Europa Subsurface
eExperiments where simple organic compounds (such as simple sugars and amino acids) were reacted with sulfides formed organomineralized elemental sulfur (S(0)), including rosickyite and ꞵ-sulfur.

 

Abiotic organomineralization of S(0) may be a widespread process in many sulfidic environments. [Congruence]

Environments
All
eOrganomineralization of S(0) has been observed in a range of geochemical conditions that encompass many sulfidic environments. 

 

Abiotic organomineralization of S(0) competes with microbial sulfide oxidation, therefore it may only be prevalent in settings where it exceeds or equals the rate of microbial S(0) biomineralization. [Congruence]

Environments
All
eOrganomineralization of S(0) competes with biomineralization and has so far only been described from lab experiments.

Abiotic greigite formation in aqueous systems is enhanced by the presence of aldehydes, and is similar in size to biogenically produced greigite in magnetosomes. [General]

Environments
Ocean Worlds: Enceladus Subsurface, Ocean Worlds: Europa Subsurface, Ocean Worlds: Titan Subsurface, Ocean Worlds: Other
eAbiogenically produced greigite in experiments where formaldehyde (HCHO) was added to iron sulfide (FeS) and hydrogen sulfide (H2S) is a similar size to biogenically produced greigite in magnetosomes.

 
Definition
HIGH
LOW

ꞵ- and 𝜸-sulfur allotropes are stable at low temperatures in the presence of simple, abiotically-produced organic compounds. [Survivability]

Environments
Ocean Worlds: Enceladus Surface, Ocean Worlds: Enceladus Subsurface, Ocean Worlds: Europa Surface, Ocean Worlds: Europa Subsurface
eIn the presence of simple sugars and amino acids, elemental sulfur (S(0)) organomineralized into stable ꞵ- and 𝜸-sulfur allotropes.