A search for polycyclic aromatic hydrocarbons over the Martian South Polar Residual Cap

Campbell, Jacqueline; Sidiropoulos, Panagiotis; Müller, Jan-Peter

doi:10.1016/j.icarus.2018.03.008

Cited by 8 publications

(2 citation statements)

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“…Work was previously carried out in order to look for PAH signatures on the thin, dust‐covered rims of SCT to no avail (Campbell et al., 2018) using the well‐known PAH diagnostic absorption feature at 3.29 µm (Allamandola, 2011), but no signs of PAHs were found. However, this strong band is situated in the high wavelength wing of the very strong 3.1 µm band of water ice and may thus be hidden in places where abundant water ice is present, such as on SPC margins (Douté et al., 2007) and rim scarps (Campbell et al., 2018). It may be also hidden by the wide hydration bands of minerals (adsorbed and structural water) that can extend up to 4 µm and may even be saturated in some cases.…”

Section: Introductionmentioning

confidence: 99%

The Detectability Limit of Organic Molecules Within Mars South Polar Laboratory Analogs

et al. 2021

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Our neighboring planet, Mars, has increasingly been the target of scientific exploration and of particular interest are its geological history, current environmental conditions, and perhaps most importantly, its potential as a host for extraterrestrial life (Fairén et al., 2010). The polar caps of Mars have more recently emerged as an area of scientific interest due to their abundance of water ice and their dynamic nature, especially with the discovery of a possible stable body of liquid water beneath the Martian South Pole (Orosei et al., 2018). The Martian North and South Pole have permanent ice caps that expand throughout their respective winters, and maintain residual caps in the summer. The North Polar Cap is composed almost entirely of water ice, while the longer, colder winter in the higher altitude southern hemisphere means that the central part Abstract A series of laboratory experiments was carried out in order to generate a diagnostic spectrum for polycyclic aromatic hydrocarbons (PAHs) of astrobiological interest in the context of the Martian South Polar Residual Cap (SPRC), to establish PAH spectral features more easily detectable in CO 2 ice (mixed with small amounts of H 2 O ice) than the previously reported absorption feature at 3.29 µm in order to constrain their detectability limit. There is currently no existing literature on PAH detection within SPRC features, making this work novel and impactful given the recent discovery of a possible subglacial lake beneath the Martian South Pole. Although they have been detected in Martian meteorites, PAHs have not been detected yet on Mars, possibly due to the deleterious effects of ultraviolet radiation on the surface of the planet. SPRC features may provide protection to fragile molecules, and this work seeks to provide laboratory data to improve interpretation of orbital remote sensing spectroscopic imaging data. We also ascertain the effect of CO 2 ice sublimation on organic spectra, as well as provide PAH reference spectra in mixtures relevant to Mars. A detectability limit of ∼0.04% has been recorded for observing PAHs in CO 2 ice using laboratory instrument parameters emulating those of the Compact Reconnaissance Imaging Spectrometer for Mars, with new spectral slope features revealed between 0.7 and 1.1 µm, and absorption features at 1.14 and most sensitively, at 1.685 µm. Mars regolith analog mixed with a concentration of 1.5% PAHs resulted in no discernible organic spectral features. These detectability limits measured in the laboratory are discussed and extrapolated to the effective conditions on the Mars South Polar Cap in terms of dust and water ice abundance and CO 2 ice grain size for both the main perennial cap and the H 2 O ice-dust sublimation lag deposit.Plain Language Summary Carbon molecule chains, or organics, are considered important in the search for life, as all life that we know of on Earth is made from carbon. A particular type of organic, PAHs, that are really common on Earth and throughout space, have never been found on Mars ...

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Section: Introductionmentioning

confidence: 99%

The Detectability Limit of Organic Molecules Within Mars South Polar Laboratory Analogs

et al. 2021

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“…Clave et al (2022) provided a list of carbonate detections, compositions, and concentrations from both orbital and in situ datasets of Mars. The list of detections is relatively extensive and include, but are not limited to, Mgrich carbonate detections in dust and rock units, Ca-Fe carbonate mixtures, and Mg-rich marginal carbonates found within Jezero crater.1.2 Organic carbon on MarsWhile carbonates have been widely detected by rovers/landers, remote reflectance spectra, and in martian meteorites, non-carbonate abiotic carbon is not observed by reflectance spectra collected from ground/air-based, orbiting, or rover spectrometers (e.g.,SingerCampbell et al, 2016). (1996) estimated a rough influx of 12x10 6 kg/year of interplanetary dust particles, which have a roughly estimated carbon content of 12 wt.%(Thomas et al, 1993).…”

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Estimated Detection Limits of Carboxylates in Palagonite by X-ray Diffraction and Reflectance Spectroscopy

Applin

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Low molecular weight carboxylates (carbonates, oxalates, formates, and acetates) are either known or are expected to be present on the surface of Mars. Previous work has suggested these phases to be present in Gale Crater materials at nearly the expected detection limit (LOD) for crystalline materials with the Mars Science Laboratory (MSL)Curiosity rover CheMin X-ray diffraction (XRD) instrument. Detection limits of these materials by CheMin-like XRD and reflectance spectroscopy are poorly constrained, thus leading to uncertainties in detectability with these types of instruments. I have filled this knowledge gap by making intimate mixtures of a variety of carboxylates with the JSC Mars-1a regolith analogue material and measured their XRD patterns with a CheMin-like breadboard and reflectance spectra with instruments analogous to the SuperCam instrument on the Mars Perseverance rover. I used simple linear regression to create calibration curves to estimate LODs and compared and contrasted ten different LOD calculations previously used for XRD. I found that the carboxylates measured have LODs near 1.0 wt.% by XRD. Oxalate minerals are likely undetectable by reflectance spectroscopy in bulk materials at expected concentrations, while acetate and formate minerals have relatively low LODs at near-infrared wavelengths due to their sharp and strong absorption bands. Carbonate minerals may show decreasing LODs with increasing grain size in reflectance spectra and have relatively high LODs at near-infrared wavelengths for fine grained powders and relatively low LODs when using the 3950 nm absorption band at all grain sizes. Application of these data to CheMin observations show that my data could accurately detect low concentrations of siderite at nearly the same values determined from previous CheMin data processing within error and within an average of 0.5-1.0 wt.% where siderite was detected. After applying the calibration curves from the other carboxylates, I did not find strong evidence for their detection in any of the CheMin data. Some samples, primarily the Gale crater Rocknest aeolian material may contain some concentration of whewellite which may be consistent with the analysis of the Sample Analysis at Mars (SAM) data, but detection may be complicated by overlapping plagioclase Bragg peaks. I applied the measured reflectance spectra from 350 to 4000 nm to some data collected by the SuperCam instrument at Jezero crater that were implied to contain organic compounds through analysis of Perseverance Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) data. I did not find evidence for carboxylates in the reflectance spectra except for Mg-rich anhydrous carbonates, and I determined the concentration to be between roughly 5.0 and 20.0 wt.%, which is broadly consistent with the previous analyses of these samples by radiative transfer modelling.

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Introduction: The 6th special issue of Mars Polar Science

Sori

Brown²

2018

Icarus

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A search for polycyclic aromatic hydrocarbons over the Martian South Polar Residual Cap

Cited by 8 publications

References 51 publications

The Detectability Limit of Organic Molecules Within Mars South Polar Laboratory Analogs

The Detectability Limit of Organic Molecules Within Mars South Polar Laboratory Analogs

Estimated Detection Limits of Carboxylates in Palagonite by X-ray Diffraction and Reflectance Spectroscopy

Introduction: The 6th special issue of Mars Polar Science

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