Orbital evidence for more widespread carbonate-bearing rocks on Mars

Probably not a substantial claim: may not pass S2 (checkable).

Martian carbonates may provide a valuable standard for interpreting any organics found on Mars.

“Martian carbonates may provide a valuable standard for interpreting any organics found on Mars [e.g., Freissinet et al., 2015]”

• cites Freissinet et al., 2015 sourceCould not verify

  The Discussion (§4.4; page unavailable) addresses the preservation and detection of Martian organics, but does not describe carbonates as a standard for interpreting them. Searches for “carbonate” and for carbonates as an interpretive standard found no passage addressing that claim. (LLM, conf=0.74)

  Experimental — accuracy not yet measured

Probably not a substantial claim: may not pass S3 (load-bearing).

Mg-rich carbonates on Mars may have a higher-temperature origin than those appearing Fe/Ca-rich.

“Romanek et al. [2009] showed that Mg incorporation into mixed-cation carbonates is much less effective at 25°C than at 70°C, which would be consistent with the Mg-rich carbonates on Mars having a higher-temperature origin than those appearing Fe/Ca-rich.”

• cites Romanek et al., 2009 sourceSupported

May combine two claims.

The authors' areas of spatially clustered carbonates in western Noachis Terra and the circum-Isidis/Terra Tyrrhena region loosely correlate with clusters of olivine exposures, although a concentration specifically surrounding Huygens basin northwest of Hellas is not observed.

“Indeed, our areas of spatially clustered carbonates in western Noachis Terra and the circum-Isidis/Terra Tyrrhena region loosely correlate with clusters of olivine exposures [e.g., Ehlmann and Edwards, 2014, Figure 2a], although a concentration specifically surrounding Huygens basin northwest of Hellas is not observed.”

• cites Ehlmann and Edwards, 2014 sourceSupported

May combine two claims.

These outcrops share a broad spectral curvature from 1 to ~1.8 μm in CRISM data, consistent with Fe-bearing carbonate, chlorite, or other ferrous phases, or possibly dehydrated Fe3+-smectite.

“These outcrops also share a broad spectral curvature from 1 to ~1.8 μm in CRISM data, consistent with Fe-bearing carbonate, chlorite, or other ferrous phases [e.g., Bishop et al., 2013c], or possibly dehydrated Fe 3+ -smectite [Morris et al., 2010a].”

• cites Bishop et al., 2013cNot matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites Morris et al., 2010aNot matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

May combine two claims.

CRISM spectra of adjacent outcrops appear dominated by hydrated Mg-phyllosilicates, and these also cooccur in the carbonate outcrops, producing water-related absorptions at 1.40 and 1.91 μm and contributing to the depth and width of the 2.3 μm band.

“CRISM spectra of adjacent outcrops appear dominated by hydrated Mg-phyllosilicates (possibly smectites), and these also cooccur in the carbonate outcrops, producing the water-related absorptions at 1.40 and 1.91 μm and contributing to the depth and width of the 2.3 μm band (Figure 3).”

May combine two claims.

These carbonates are found in and around the Huygens basin northwest of Hellas, in western Noachis Terra between the Argyre basin and Valles Marineris, and in other isolated locations spread widely across the planet.

“These carbonates are found in and around the Huygens basin northwest of Hellas, in western Noachis Terra between the Argyre basin and Valles Marineris, and in other isolated locations spread widely across the planet.”

May combine two claims.

The carbonate-bearing rocks in Lucaya are jointed and possibly layered and in some places are criss-crossed by protruding ridges that could be dikes or large mineralized veins.

“The carbonate-bearing rocks are jointed and possibly layered (Figure 6a) and in some places are criss-crossed by protruding ridges (Figure 6b) that could be dikes or large mineralized veins.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Several of these craters, such as Lucaya and the unnamed crater in Figure 4, contain central pits.

“Several of these craters, such as Lucaya and the unnamed crater in Figure 4, contain central pits.”

May combine two claims.

In Lucaya crater, carbonate and phyllosilicate-bearing materials can be mapped to specific outcrops on the central pit wall; the strongest signatures are seen on the southeastern side, but smaller carbonate outcrops occur across the pit's ~6 km width.

“Here carbonate and phyllosilicate-bearing materials can be mapped to specific outcrops on the central pit wall (Figure 5c); the strongest signatures are seen on the southeastern side, but smaller carbonate outcrops occur across the pit's ~6 km width (e.g., bright outcrops on the northern wall at 11.545°S, 51.922°E).”

May combine two claims.

Aragonite has a more complex spectral structure at ~3.4 μm that the authors do not observe in the Huygens data, but other Ca/Fe-carbonates (calcite, ankerite, and siderite) appear equally consistent with the vibrational bands detected by CRISM.

“Aragonite has a more complex spectral structure at ~3.4 μm that we do not observe in the Huygens data, but other Ca/Fe-carbonates (calcite, ankerite, and siderite) appear equally consistent with the vibrational bands detected by CRISM [see also Bishop et al., 2015].”

• cites Bishop et al., 2015Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

May combine two claims.

Other confirmed carbonate detections on Huygens' rim or its proximal ejecta appear excavated from comparable depths, but not all deep rim exposures reveal unambiguous carbonates; e.g., FRT00021DF7 covers a D ~25 km central pit crater on Huygens' eastern rim exposing phyllosilicates, but no carbonates.

“Other confirmed carbonate detections on Huygens' rim or its proximal ejecta appear excavated from comparable depths, but not all deep rim exposures reveal unambiguous carbonates; e.g., FRT00021DF7 covers a D ~25 km central pit crater on Huygens' eastern rim exposing phyllosilicates, but no carbonates (Figure 2).”

May combine two claims.

Carbonates are also found within Huygens basin as well as on its rim.

“Carbonates are also found within Huygens basin as well as on its rim.”

May combine two claims.

Huygens has an uplifted central peak ring; carbonates on the basin floor all occur outside this ring, mostly adjacent to the dissected basin walls, and could have been eroded and transported from the basin rim.

“Huygens has an uplifted central peak ring; carbonates on the basin floor all occur outside this ring, mostly adjacent to the dissected basin walls, and could have been eroded and transported from the basin rim.”

May combine two claims.

Carbonates occur from the north end of the basin to the south, exposed by craters or, in one case, at the eroding edge of a dendritic (fluvial?) feature downslope from the basin wall-incising valleys.

“They occur from the north end of the basin to the south, Journal of Geophysical Research: Planets 10.1002/2015JE004972 exposed by craters (Figure 4) [see also Wray et al., 2009, Figure DR1C] or, in one case, at the eroding edge of a dendritic (fluvial?)feature downslope from the basin wall-incising valleys (Figure 8).”

• cites Wray et al., 2009 sourceNot checked — no full text of the source

May combine two claims.

Lucaya's valleys are filled with younger aeolian bed forms, which appear to be inactive, as several small impact craters are superposed on them.

“Lucaya's valleys are filled with younger aeolian bed forms (Figure 6a), which appear to be inactive, as several small impact craters are superposed on them.”

May combine two claims.

A D ~32 km crater on Huygens' southwest flank showed chlorite but no clear carbonates in its central uplift at ~36 m/pixel (CRISM HRS00019650), whereas at ~18 m/pixel (FRT0001FD79) carbonates are resolved, likely originating from a depth similar to those in Lucaya.

“For example, a D ~32 km crater on Huygens' southwest flank (Figure 7a) showed chlorite but no clear carbonates in its central uplift at ~36 m/pixel (CRISM HRS00019650), whereas at ~18 m/pixel (FRT0001FD79) carbonates are resolved (Figure 7b), likely originating from a depth similar to those in Lucaya.”

May combine two claims.

Clay and carbonate are detected in Her Desher Vallis and Nirgal Vallis.

“Arrows point to locations of clay + carbonate detection in Her Desher Vallis (CRISM HRL00009B61) and Nirgal Valllis (FRT0000C875).”

May combine two claims.

Carbonates in Noachis Terra cooccur with layered phyllosilicates in the shallow subsurface and could be younger.

“Carbonates in Noachis Terra cooccur with layered phyllosilicates in the shallow subsurface and could be younger.”

May combine two claims.

The 3-4 μm features in the Holden lower unit are at the noise level, and the shape and width of the 2.5 μm feature do not closely match the rounded, asymmetric 2.5 μm absorptions in the authors' laboratory carbonate spectra.

“However, the 3-4 μm features are at the noise level (Figure 14d), and the shape and width of the 2.5 μm feature do not closely match the rounded, asymmetric 2.5 μm absorptions in our Journal of Geophysical Research: Planets 10.1002/2015JE004972 laboratory carbonate spectra (Figure 1)”

May combine two claims.

Layered or foliated rocks in the unnamed crater in eastern Hesperia Planum have a mixed composition including Mg-carbonate (concentrated in lighter-toned rocks at right), Fe/Mg-clay (concentrated in redder materials to the left), and possibly weathered glass.

“Layered or foliated rocks of mixed composition including Mg-carbonate (concentrated in the lighter-toned rocks at right), Fe/Mg-clay (concentrated in redder materials to the left), and possibly weathered glass”

May combine two claims.

CRISM hyperspectral mapping shows that ~2.5 and ~3.9 μm absorptions consistent with carbonate span several kilometers of phyllosilicate-rich outcrop laterally at Her Desher Vallis but are not ubiquitous within this layer.

“CRISM hyperspectral mapping shows that ~2.5 and ~3.9 μm absorptions consistent with carbonate span several kilometers of phyllosilicate-rich outcrop laterally at this location but are not ubiquitous within this layer (Figure 11).”

May combine two claims.

Continuum-removed spectra show rounded 2.30 and 2.50 μm absorptions of comparable strength in some Hesperia outcrops, consistent with Mg-carbonate, while in other locations the 2.3 μm band is stronger and other features indicate mixture with Fe/Mg-phyllosilicates.

“In any case, continuum-removed spectra clearly show rounded 2.30 and 2.50 μm absorptions that are of comparable strength in some outcrops, consistent with Mg-carbonate, while in other locations the 2.3 μm band is stronger and other features (e.g., a 1.4 μm absorption) indicate mixture with Fe/Mg-phyllosilicates”

May combine two claims.

In Her Desher Vallis, carbonate mapped using CINDEX corresponds to all yellow areas in Figure 11a (spectra having both 2.3 and 2.5 μm absorptions), but not areas that are red in Figure 11a (having only a 2.3 μm band).

“Note correspondence to all yellow areas in Figure11a(i.e., spectra having both 2.3 and 2.5 μm absorptions), but not areas that are red in Figure11a(i.e., having only a 2.3 μm band).”

May combine two claims.

At ~36 m/pixel, the outcrop in Figure 7a has a spectrum resembling chlorite, with a strong 3 μm H2O band, weaker ~2.5 than ~2.3 μm feature, and clear shoulder at 2.25 μm.

“At ~36 m/pixel (HRS 19650), after averaging enough pixels to mitigate noise, the outcrop in Figure 7 a has a spectrum resembling chlorite, with a strong 3 μm H 2 O band, weaker ~2.5 than ~2.3 μm feature, and clear shoulder at 2.25 μm (arrow).”

May combine two claims.

In Holden crater, a 2.5 μm absorption is found only in the outcrop possibly containing carbonate (Figure 14a), which also has a stronger 3.9 μm band and a ~3.5 μm region more consistent with carbonate than in the clay-bearing outcrop (Figure 14b).

“Arrow indicates a 2.5 μm absorption found only in Figure14a, which also has a stronger 3.9 μm band and a (d) ~3.5 μm region more consistent with carbonate than in Figure14b.”

May combine two claims.

Additional CRISM imaging shows that these signatures are localized to the central uplift and adjacent crater floor and not found in the crater's reasonably well-preserved ejecta.

“Additional CRISM imaging in and around this crater shows that these signatures are localized to the central uplift and the adjacent crater floor and not found in the crater's reasonably well-preserved ejecta (Figure 15a).”

May combine two claims.

The darker subunit at the top of the clay-bearing horizon in Her Desher Vallis extends for at least several kilometers and appears deficient in carbonate relative to the underlying, polygonally fractured outcrop.

“The darker subunit at the top of the clay-bearing horizon extends for at least several kilometers and appears deficient in carbonate relative to the underlying, polygonally fractured outcrop.”

May combine two claims.

Spectra from the central pit and ejecta of the central pit crater on Huygens floor show similar characteristics to each other and to the CRISM spectrum in Figure 3.

“Spectra from the crater's central pit (top) and ejecta (middle, bottom) show similar characteristics to each other and to the CRISM spectrum in Figure 3.”

Probably not a substantial claim: may not pass S3 (load-bearing).

The two spectral averages from the unnamed crater in eastern Hesperia Planum show broad blue slopes that extend to the longest wavelengths measured by CRISM.

“The same two spectral averages prior to continuum removal, showing broad blue slopes that extend to the longest wavelengths measured by CRISM.”

May combine two claims.

The IR spectral features of two Fe-oxalate minerals are notably distinct from those of carbonates or Fe/Mg-phyllosilicates, lacking ~2.3 μm features but with distinctive absorptions at ~1.6 and 2 μm (ferrous) or ~0.6 μm (ferric).

“Their IR spectral features are notably distinct from those of carbonates or Fe/ Mg-phyllosilicates, lacking ~2.3 μm features but with distinctive absorptions at ~1.6 and 2 μm (ferrous) or ~0.6 μm (ferric).”

May combine two claims.

The detailed spatial distribution of mineral signatures suggests that the phyllosilicate signatures are concentrated in the ridged areas, which could indicate that they represent a later stage of alteration.

“The detailed spatial distribution of mineral signatures (Figure 5c) suggests that the phyllosilicate signatures are concentrated in the ridged areas, which could indicate that they represent a later stage of alteration.”

Classified as probably not a substantial claim.

The 3.9 μm band depth is considered as evidence for carbonates only in scenes where it appears spatially correlated with the 2.3 and 2.5 μm band depths.

“The 3.9 μm band depth is considered as evidence for carbonates only in scenes where it appears spatially correlated with the 2.3 and 2.5 μm band depths.”

May combine two claims.

Release of CO2 and H2O from carbonate- and phyllosilicate-rich target rocks may have formed Lucaya's central pit, and the valleys emptying into it could perhaps have been carved by impact-mobilized fluids.

“Release of CO 2 [e.g., Hörz et al., 2015] and H 2 O from carbonate-and phyllosilicate-rich target rocks may have formed Lucaya's central pit, and the valleys emptying into it (Figure 5) could perhaps have been carved by impact-mobilized fluids; such valleys in central pit craters are otherwise relatively rare at the ice-poor equatorial latitudes of Mars [Peel and Fassett, 2013].”

• cites Hörz et al., 2015Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites Peel and Fassett, 2013 sourceNot checked — no full text of the source

May combine two claims.

The preimpact depth of these materials in the adjacent D ~21 km crater can be no greater than a few hundred meters, indicating that carbonates may occur at varying depths across the region.

“Here the preimpact depth of these materials can be no greater than a few hundred meters, indicating that carbonates may occur at varying depths across the region.”

May combine two claims.

Mg-carbonate has been confirmed in situ by Spirit in Gusev crater, where the Comanche outcrop hosts 16-34 wt % carbonate as estimated by three complementary chemical and mineralogical data sets.

“Mgcarbonate has also been confirmed in situ by Spirit in Gusev crater, where the Comanche outcrop hosts 16-34 wt % carbonate as estimated by three complementary chemical and mineralogical data sets [Morris et al., 2010b].”

• cites Morris et al., 2010bNot matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

Classified as probably not a substantial claim. May combine two claims.

Previous remote sensing studies have identified mostly Mg-rich carbonates, both in Martian dust and in a Late Noachian rock unit circumferential to the Isidis basin.

“Previous remote sensing studies have identified mostly Mg-rich carbonates, both in Martian dust and in a Late Noachian rock unit circumferential to the Isidis basin.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

The authors make no attempt to model and remove the thermal emission that competes with surface reflectance at the longest wavelengths, and many observations still show spectral structure in the 3-4 μm range that they do not fully understand.

“We do so with the caveats that we make no attempt to model and remove the thermal emission that competes with surface reflectance at the longest wavelengths and that many observations still show spectral structure in the 3-4 μm range that we do not fully understand.”

May combine two claims.

Nonthermal escape processes appear capable of removing only up to ~10 mbar or at most ~100 mbar CO2 over the past 4.1 Gyr, so another sink for the early atmosphere is needed.

“Nonthermal escape processes appear capable of removing only up to ~10 mbar [e.g., Chassefière et al., 2013] or at most ~100 mbar CO 2 over the past 4.1 Gyr [Lammer et al., 2013], so another sink for the early atmosphere is needed.”

• cites Chassefière et al., 2013 sourceNot checked — no full text of the source
• cites Lammer et al., 2013 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Indurated cross strata are visible among these bed forms, suggesting that later fluids may have dissolved some carbonates and reprecipitated them as sand cements.

“Indurated cross strata are visible among these bed forms, suggesting that later fluids may have dissolved some carbonates and reprecipitated them as sand cements [Bourke and Wray, 2011].”

• cites Bourke and Wray, 2011Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

May combine two claims.

Thermal infrared studies of several candidate basins revealed no abundant carbonates, and the Spirit rover's landing site in Gusev crater was found to be covered in basaltic lavas rather than carbonate-rich sediments.

“Thermal infrared studies of several candidate basins revealed no abundant carbonates [Ruff et al., 2001;Stockstill et al., 2005Stockstill et al., , 2007]], and the Spirit rover's landing site in Gusev crater-a likely former lake basin-was found to be covered in basaltic lavas rather than carbonate-rich sediments [Squyres et al., 2004].”

• cites Ruff et al., 2001 sourceNot checked — no full text of the source
• cites Stockstill et al., 2005Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites Squyres et al., 2004 sourceNot checked — no full text of the source

May combine two claims.

The broad ~3 μm H2O absorptions of phyllosilicates reduce the spectral contrast of carbonates' ~3.4 μm features, but the latter remains discernible when carbonate is equal or even a bit less abundant than smectite, as do the ~2.5 and ~3.9 μm absorptions.

“The broad ~3 μm H 2 O absorptions of phyllosilicates also reduce the spectral contrast of carbonates' ~3.4 μm features, but the latter nevertheless remains discernible when carbonate is equal or even a bit less abundant than smectite, as do the ~2.5 and ~3.9 μm absorptions [Bishop et al., 2013b].”

• cites Bishop et al., 2013bNot matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

May combine two claims.

Ca/Fe-carbonates have also been reported in two crater central uplifts in Terra Tyrrhena, in the walls of a crater into Noachian materials in the Eridania basin, in Capri Chasma at the eastern end of Valles Marineris, and on the floor of Robert Sharp crater just west of Gale crater.

“Ca/Fe-carbonates have also been reported in two crater central uplifts in Terra Tyrrhena [Carrozzo et al., 2013], in the walls of a crater into Noachian materials in the Eridania basin [Gilmore et al., 2014;Korn and Gilmore, 2015], in Capri Chasma at the eastern end of Valles Marineris [Jain and Chauhan, 2015], and on the floor of Robert Sharp crater just west of Gale crater [Carter et al., 2015].”

• cites Carrozzo et al., 2013Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites Gilmore et al., 2014Not checked — no full text of the source
• cites Jain and Chauhan, 2015 sourceNot checked — no full text of the source

May combine two claims. The quote only partly states this claim.

Spectra such as Figure 12a are interpreted as combinations of carbonates and clays, with Ca-carbonate best fitting the 2.54 and ~3.5 μm absorptions, while Fe/Mg-smectite, perhaps at equal or somewhat higher abundance, explains the narrower minimum at 2.30 μm, the weak absorption at ~2.4 μm, and the absorptions at 1.4, 1.9, and 3 μm.

“Thus, we interpret spectra such as that shown in Figure 12a (same as Figure 1, bottom) as combinations of carbonates and Journal of Geophysical Research: Planets Journal of Geophysical Research: Planets clays, with Ca-carbonate best fitting the 2.54 and ~3.5 μm absorptions”

Probably not a substantial claim: may not pass S3 (load-bearing).

Crater floor pits throughout the solar system are thought to form from impacts into volatile-rich targets, generating impact melt that later drains into subsurface fractures, while its most volatile components are lost via vaporization.

“Crater floor pits throughout the solar system are thought to form from impacts into volatile-rich targets, generating impact melt that later drains into subsurface fractures, while its most volatile components are lost via vaporization [e.g., Alzate and Barlow, 2011;Bray et al., 2012;Tornabene et al., 2012].”

• cites Alzate and Barlow, 2011 sourceNot checked — no full text of the source
• cites Bray et al., 2012 sourceNot checked — no full text of the source
• cites Tornabene et al., 2012 sourceNot checked — no full text of the source

May combine two claims.

The Fe/Mg-phyllosilicate layer is tens of meters thick and is exposed continuously along impact crater rims, valley walls, and other locations throughout the region where erosion has revealed the subsurface stratigraphy.

“This layer is tens of meters thick and is exposed continuously along impact crater rims, valley walls, and other locations throughout the region where erosion has revealed the subsurface stratigraphy [Buczkowski et al., 2010[Buczkowski et al., , 2013;;Le Deit et al., 2012].”

• cites Buczkowski et al., 2010Not checked — no full text of the source
• cites Buczkowski et al., 2013Not checked — no full text of the source
• cites Le Deit et al., 2012 sourceNot checked — no full text of the source

May combine two claims.

Ancient atmospheric CO2 could have been sequestered via dissolution in surface waters, yielding HCO3- and CO3 2- ions that combined with cations weathered from silicate crustal material, forming carbonate minerals.

“Ancient atmospheric CO 2 could also have been sequestered via dissolution in surface waters, yielding HCO 3 -and CO 3 2-ions that combined with cations weathered from silicate crustal material, forming carbonate minerals [e.g., O'Connor, 1968;Goldspiel and Squyres, 1991].”

• cites O'Connor, 1968 sourceNot checked — no full text of the source
• cites Goldspiel and Squyres, 1991 sourceNot checked — no full text of the source

May combine two claims.

The coarser resolution of TES and THEMIS relative to CRISM, plus textural effects such as high porosity, make definitive identification challenging for small deposits, but possible for the largest known deposits where exposures are at kilometer scales.

“The coarser resolution of TES and Mars Odyssey's Thermal Emission Imaging System (THEMIS) relative to CRISM, plus textural effects such as high porosity [Kirkland et al., 2003], make definitive identification challenging for small deposits, but possible for the largest known deposits where exposures are at kilometer scales [Edwards and Ehlmann, 2015].”

• cites Kirkland et al., 2003 sourceNot checked — no full text of the source
• cites Edwards and Ehlmann, 2015 sourceNot checked — no full text of the source

May combine two claims.

Carbonates can also form in thin H2O films under the dry conditions of modern Mars, but this process appears to be self-limiting and could likely store only a few tens of millibars CO2 and may require precursor minerals not known to exist widely on Mars, such as portlandite.

“Carbonates can also form in thin H 2 O films under the dry conditions of modern Mars [Booth and Kieffer, 1978;Shaheen et al., 2010], but this process appears to be self-limiting and could likely store only a few tens of millibars CO 2 [Stephens and Stevenson, 1990;Stephens et al., 1995] and also may require precursor minerals not known to exist widely on Mars, such as portlandite [Garenne et al.,”

• cites Booth and Kieffer, 1978 sourceNot checked — no full text of the source
• cites Shaheen et al., 2010 sourceNot checked — no full text of the source
• cites Stephens and Stevenson, 1990Not checked — no full text of the source

May combine two claims.

These carbonate-bearing rocks appear layered, and at least some were likely once buried several kilometers or more beneath the surface.

“These carbonate-bearing rocks appear layered, and at least some were likely once buried several kilometers or more beneath the surface.”

May combine two claims.

Fluids across the Noachis Terra region may have remained nonacidic longer than elsewhere on Mars, allowing both the carbonates and clays to persist and be fluvially transported to regional basins.

“Fluids across this region may have remained nonacidic longer than elsewhere on Mars, allowing both the carbonates and clays to persist and be fluvially transported to regional basins.”

May combine two claims.

Their occurrence across a region >2000 km wide implies that the layered Fe/Ca-carbonate found in Leighton crater's central uplift is but one of many windows into a record of possibly widespread, neutral-to-alkaline aqueous conditions during the pre-Noachian period, preserved mostly in the subsurface.

“Their occurrence across a region >2000 km wide implies that the layered Fe/Ca-carbonate found in Leighton crater's central uplift by Michalski and Niles [2010] is but one of many windows into a record of possibly widespread, neutral-to-alkaline aqueous conditions during the pre-Noachian period, preserved mostly in the subsurface.”

• cites Michalski and Niles, 2010 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing).

Buried carbonates could have provided a source of carbon for metabolism in the deep crust isolated from atmospheric CO2.

“buried carbonates could have provided a source of carbon for metabolism in the deep crust isolated from atmospheric CO 2 [Kral et al., 2014].”

• cites Kral et al., 2014 sourceNot checked — no full text of the source

May combine two claims.

Light-toned layered deposits on the Holden crater floor contain clay minerals, with an additional component that varies spatially and may be carbonate.

“Light-toned layered deposits on the crater floor contain clay minerals (yellow arrows), with an additional component that varies spatially and may be carbonate.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Fe/Ca-carbonates could have formed from more dilute waters, whereas more soluble Mg-carbonates could record locations of later brines more concentrated by evaporative or cryogenic processes.

“Alternatively, the Fe/Ca-carbonates could have formed from more dilute waters, whereas the more soluble Mg-carbonates could record locations of later brines more concentrated by evaporative or cryogenic processes [Hardie and Eugster, 1970;Tosca and McLennan, 2006].”

• cites Hardie and Eugster, 1970Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites Tosca and McLennan, 2006 sourceNot checked — no full text of the source

May combine two claims.

The lowermost sedimentary layer in Holden crater has the strongest clay signatures, consistent with ~25-45% phyllosilicates by volume.

“The lowermost sedimentary layer-labeled the lower unit, lower member in the stratigraphy of Grant et al. [2008]-has the strongest clay signatures [Milliken and Bish, 2010], consistent with ~25-45% phyllosilicates by volume [Poulet et al., 2014].”

• cites Milliken and Bish, 2010 sourceNot checked — no full text of the source
• cites Poulet et al., 2014 sourceNot checked — no full text of the source

May combine two claims.

A 40% carbonate abundance is a reasonable estimate given the presence of cooccurring phyllosilicates while carbonate nonetheless dominates the ~2.3 μm region.

“Given the presence of cooccurring phyllosilicates while carbonate nonetheless dominates the ~2.3 μm region, 40% carbonate is a reasonable estimate [Bishop et al., 2013b].”

• cites Bishop et al., 2013bNot matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

May combine two claims.

The association of Fe/Ca-carbonates with complex craters-including Leighton and those around the Huygens basin-suggests impact-related formation and/or exposure of previously buried carbonate.

“The association of Fe/Ca-carbonates with complex craters-including Leighton [Michalski and Niles, 2010] and those around the Huygens basinsuggests impact-related formation and/or exposure of previously buried carbonate.”

• cites Michalski and Niles, 2010 sourceNot checked — no full text of the source

May combine two claims.

Early burial could have protected these carbonates from later decomposition due to surface acidity, helping to explain why few large exposures of carbonate-rich rocks have been identified.

“Early burial could have protected these carbonates from later decomposition due to surface acidity [Bibring et al., 2006], helping to explain why few large exposures of carbonate-rich rocks have been identified.”

• cites Bibring et al., 2006 sourceNot checked — no full text of the source

Classified as probably not a substantial claim. May combine two claims.

The spatial distribution of secondary minerals in the Hesperia crater could be consistent with being the deepest preexisting material excavated there, reaching the surface only in the structurally uplifted central peak (~4.5 km estimated preimpact burial depth), or alternatively could have resulted from impact-induced hydrothermal alteration.

“Secondary minerals having this spatial distribution could be consistent with being the deepest preexisting material excavated here, reaching the surface only in the structurally uplifted central peak (~4.5 km estimated preimpact burial depth), but alternatively could have resulted from impact-induced hydrothermal alteration.”

May combine two claims.

If Lucaya's carbonate layer spans only the entire area of Huygens crater, it would represent a reservoir most likely of a few millibars, or potentially up to double this amount if additional outcrops surrounding the Isidis basin are included.

“At the other extreme, if Lucaya's carbonate layer spans only the entire area of Huygens crater (but is only exposed at the locations observed), then it would represent a reservoir more comparable to that estimated for Nili Fossae by Edwards and Ehlmann [2015]; most likely a few millibars, or potentially up to double this amount if additional outcrops surrounding the Isidis basin are also included”

• cites Edwards and Ehlmann, 2015 sourceNot checked — no full text of the source
• cites Viviano-Beck, 2015Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• AssumptionThe authors state this as an assumption: The global versus regional nature of deep carbonates is uncertain.

May combine two claims.

The Huygens carbonates would also predate the Late Noachian Mg-carbonates near Isidis and layered phyllosilicates across Mars.

“in which case they would also predate the Late Noachian Mg-carbonates near Isidis [Ehlmann et al., 2008[Ehlmann et al., , 2009;;Bishop et al., 2013a] and layered phyllosilicates across Mars [e.g., Murchie et al., 2009a;Ehlmann et al., 2011].”

• cites Ehlmann et al., 2008 sourceNot checked — no full text of the source
• cites Bishop et al., 2013aNot matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites Murchie et al., 2009aNot matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

May combine two claims.

Holden was a sink for sediments that likely sampled materials to its west that show stronger evidence for a carbonate component.

“Still, Holden was a sink for sediments that likely sampled the materials to its west that show stronger evidence for a carbonate component.”