NH₄‐Smectites as Potential Precursors of Nitrogen Compounds Evolved During Analyses by the Sample Analysis at Mars (SAM) Instrument on the Curiosity Rover
Abstract
Ammonium (NH₄⁺) in the interlayer space of phyllosilicates has been proposed as a potential but underexplored nitrogen reservoir on Mars. We synthesized ammonium‐exchanged smectites (montmorillonite SWy‐2 and nontronite NAu‐2) and analyzed them, both as pure phases and in mixtures containing five or 20 wt.% magnesium (Mg) perchlorate, under Sample Analysis at Mars (SAM)–like conditions using evolved gas analysis–mass spectrometry (EGA) and pyrolysis (GC‐MS), complemented by FTIR, XRD and EA‐IRMS. Ammoniated smectites released N₂ during heating even without perchlorate, whereas mixtures with Mg perchlorate yielded oxidized nitrogen species (NO and N₂O) along with N₂. The temperature ranges and release profiles of NO bear similarities to several Gale crater samples analyzed by SAM, suggesting that part of the martian NO could derive from ammonium‐bearing smectites rather than exclusively from nitrate thermal decomposition. Quantitative analysis of EGA data indicates that 4.20%–29.8% of the total nitrogen in the ammoniated smectites was released as NO under SAM‐like pyrolysis, depending on smectite type and oxidant abundance. XRD under dry conditions shows partial collapse of basal spacing to d(001) ≈10.8 Å (NH₄ SWy‐2) and 10.4 Å (NH₄NAu‐2), comparable to the broad ∼10 Å peaks observed by the Chemistry and Mineralogy (CheMin) instrument in clay‐bearing Gale crater materials. These results indicate that ammonium‐bearing smectites are a plausible precursor phase capable of generating NO under SAM‐like pyrolysis conditions and could contribute to martian nitrogen cycling in environments where smectite formation and ammonium exchange occurred, although the present martian data do not uniquely distinguish among possible nitrogen precursor phases.
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BibTeX
@article{andrejkovicova2026nh₄smectites,
title = {{NH₄‐Smectites as Potential Precursors of Nitrogen Compounds Evolved During Analyses by the Sample Analysis at Mars (SAM) Instrument on the Curiosity Rover}},
author = {Slavka Andrejkovičová and Amy Mcadam and Jennifer C Stern and Maeva Millan and Rafael Navarro-González and Christine A Knudson and Scott T Wieman and Elizabeth B Rampe and Douglas W Ming and Cherie N Achilles and Stacey Johnson and Fernando Rocha and Charles A Malespin and Paul R Mahaffy},
journal = {Journal of Geophysical Research. Planets},
year = {2026},
month = oct,
doi = {10.1029/2025je009610},
url = {https://hal.science/hal-05838933v1},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - JOUR
TI - NH₄‐Smectites as Potential Precursors of Nitrogen Compounds Evolved During Analyses by the Sample Analysis at Mars (SAM) Instrument on the Curiosity Rover
AU - Slavka Andrejkovičová
AU - Amy Mcadam
AU - Jennifer C Stern
AU - Maeva Millan
AU - Rafael Navarro-González
AU - Christine A Knudson
AU - Scott T Wieman
AU - Elizabeth B Rampe
AU - Douglas W Ming
AU - Cherie N Achilles
AU - Stacey Johnson
AU - Fernando Rocha
AU - Charles A Malespin
AU - Paul R Mahaffy
PY - 2026
DA - 2026/10/19
JO - Journal of Geophysical Research. Planets
DO - 10.1029/2025je009610
UR - https://hal.science/hal-05838933v1
AB - Ammonium (NH₄⁺) in the interlayer space of phyllosilicates has been proposed as a potential but underexplored nitrogen reservoir on Mars. We synthesized ammonium‐exchanged smectites (montmorillonite SWy‐2 and nontronite NAu‐2) and analyzed them, both as pure phases and in mixtures containing five or 20 wt.% magnesium (Mg) perchlorate, under Sample Analysis at Mars (SAM)–like conditions using evolved gas analysis–mass spectrometry (EGA) and pyrolysis (GC‐MS), complemented by FTIR, XRD and EA‐IRMS. Ammoniated smectites released N₂ during heating even without perchlorate, whereas mixtures with Mg perchlorate yielded oxidized nitrogen species (NO and N₂O) along with N₂. The temperature ranges and release profiles of NO bear similarities to several Gale crater samples analyzed by SAM, suggesting that part of the martian NO could derive from ammonium‐bearing smectites rather than exclusively from nitrate thermal decomposition. Quantitative analysis of EGA data indicates that 4.20%–29.8% of the total nitrogen in the ammoniated smectites was released as NO under SAM‐like pyrolysis, depending on smectite type and oxidant abundance. XRD under dry conditions shows partial collapse of basal spacing to d(001) ≈10.8 Å (NH₄ SWy‐2) and 10.4 Å (NH₄NAu‐2), comparable to the broad ∼10 Å peaks observed by the Chemistry and Mineralogy (CheMin) instrument in clay‐bearing Gale crater materials. These results indicate that ammonium‐bearing smectites are a plausible precursor phase capable of generating NO under SAM‐like pyrolysis conditions and could contribute to martian nitrogen cycling in environments where smectite formation and ammonium exchange occurred, although the present martian data do not uniquely distinguish among possible nitrogen precursor phases.
SN - 2169-9097
SN - 2169-9100
ER -