Amorphous Ferric Sulfate data Associated with NSF award #1819209

These are the data collected for NSF Astronomy Award number 1819209.

The major goals of this project were:

Determine the stability and transformation products of amorphous ferric sulfate salts and salt mixtures formed in the presence of common Martian regolith components of varying grain sizes;

Measure the spectra of regolith materials coated by amorphous ferric sulfate salts/amorphous mixed salts and compare them to spectra of (1) regolith materials mixed with those amorphous phases and (2) regolith materials mixed with nanophase crystalline sulfates;

Use our laboratory spectra to search for and map the presence of amorphous ferric sulfates, amorphous mixed salts, and amorphous salt coatings in Mars Reconnaissance Orbiter Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) and Mars Global Surveyor Thermal Emission Spectrometer (TES) data.

These were divided into the following subtasks:

1a) Monitor the evolution of mixtures over time at 11% and 33% relative humidity (RH) at both room temperature (RT; Done) and 255K with the goals of determining time to deliquescence and the evolution of phases with time.

1b) Compare XRD results of amorphous mixtures to those of nanophase ferricopiapite mixed with the same regolith analogues with and without being subjected to vacuum dehydration.

2a) Study the spectroscopic features (UV, VNIR, FTIR, Raman) and XRD at RT of target mixtures deliquesced and then dehydrated either at low RH or by vacuum at RT.

2b) Study the spectroscopic features (UV, VNIR, emissivity, Raman, Mossbauer) and XRD at 255K of target mixtures deliquesced and then dehydrated at low RH or by vacuum at 255K.

3a) Identify unique spectral characteristics in the VNIR of these mixtures and create spectral rules for identifying these mixtures using the Tetracorder system.

3b) Search for amorphous mixtures in CRISM data using Tetracorder.

3c) Search for amorphous mixtures in TES data using low temperature emissivity data.

Due to the impact of COVID, much of this work was performed but was not published. This repository is aimed at making these data available for the scientific community to use in their investigations on similar systems,

These data are publicly available as reference spectra and should reference the DOI of this repository.

Additional citations for this work include:

Hopkins et al. (2023) A Spectroscopic Study of Mars-Analog Materials with Amorphous Sulfate and Chloride Phases: Implications for Detecting Amorphous Materials on the Martian Surface, Planetary Science Journal, 4:173. doi:10.3847/PSJ/aced52

Hopkins, R. J. and E. C. Sklute (2021) Chemical and spectral properties of iron-sulfate acid solutions through a hydration/dehydration cycle: Implications for the Martian regolith, 52nd LPSC, Abstract #1534.

Hopkins, R. J., A. D. Rogers, L. Ehm, and E. C. Sklute (2021) FTIR-ATR spectra and XRD analysis of Amorphous sulfate-chloride brine desiccation products after multiple consecutive deliquescence-desiccation cycles, Brines Across the Solar System, Abstract #6031.

Sklute, E. C., A. E. Geist, B. Koretke, J. F. King, R. J. Hopkins, A. D. Rogers, R. Clark, and M. D. Dyar (2021) Alteration of common regolith analogues and precipitation products from rapidly dehydrated ferric sulfate saturated brines in the presence and absence of NaCl — A story of amorphous Mars, Brines Across the Solar System, Abstract #6039.

Sklute, E. C., R. J. Hopkins, R. McKeegan, M. D. Dyar, A. D. Rogers, and R. N. Clark (2021) Raman spectra of amorphous ferric sulfate reacted with Mars regolith analogues: A compatible technique to assist in XRD identification, 52nd LPSC, Abstract #2659.

Sklute, E. C., R. J. Hopkins, R. McKeegan, M. D. Dyar, A. D. Rogers, R. L. Clark (2020) Another potential route to Martian jarosites: Reaction products of hydration-dehydration cycling of ferric sulfate–regolith mixtures, 51st LPSC, Abstract #1710.

Sklute, E. C., R. J. Hopkins, R. McKeegan, M. D. Dyar, A. D. Rogers, R. L. Clark (2020) VNIR and FTIR spectra of amorphous ferric sulfate reacted with Martian analogues: Spectral differences between concretions and powders, 51st LPSC, Abstract #2051.

Hopkins, R. J., E. C. Sklute, R. McKeegan, M. D. Dyar, D. A. Rogers, R. C. Clark (2020) Infrared spectra of vacuum-dehydrated iron-sulfate acid solutions: Implications for the Martian regolith, 51st LPSC, Abstract #1684.

NAMING CONVENTIONS

All binary mixtures are 50 wt% regolith analog and 50 wt% amorphous ferric sulfate (or nanophase ferricopiapite)

All mixtures including NaCl are 33% regolith analog, 33 wt% amorphous ferric sulfate (or nanophase ferricopiapite), and 33% NaCl

B =  Hawaiian basaltic glass

N = Nontronite NaU-1

M = Magnesite (S) is a stony magnesite with a slight quartz contamination and (N) is a softer nugget magnesite with a small amount of organics

H = Hematite kidney ore from Cornwall, UK with a slight quartz contamination

G = Gypsum (pure selenite)

Sample names look like

DateAquired_SampleNameDehydrationConditionTemp_DateDehydrated

Date format is YYMMDD## for all except Raman, which are YYMMDD###

extensions are

XRD: *.rasx, *.xy, and sometimes *.txt

VNIR: *.asd (raw), *.asd.sco (splice corrected), *.asd.sco.txt (csv files)

FTIR: *.0 (OPUS file format), *.dpt (data point table that can be opened in a plotting program), *.txt also used

Raman: *.0 (OPUS file format), *.dpt (data point table that can be opened in a plotting program), *.txt also used. Raman file names are one digit longer than FTIR filenames.

For example

22032205_MNa11LT_020822.rasx is a Rigaku XRD file taken 03/22/2022. It was the fifth sample taken that day. The XRD is of a mixture of magnesite (M), sodium chloride (Na), and amorphous ferric sulfate, hydrated at 92% RH and then dehydrated at 11%RH and at 255K (LT) starting on 02/08/22.

Dehydration conditions are 11%: LiCl buffering salt; 33% MgCl buffering salt at 295K and KCl or K

The two Excel log sheets can be used as a guide for which analyses have been performed on which samples thus allowing for a quick way to find all analyses performed on a particular sample at a particular time point. 

Associated optical photographs for samples across the entire time- and experimental- parameter space can be requested from [e-mail] and many can be found at https://www.lionsandlamms.com/.