Orbital evidence for more widespread carbonate-bearing rocks on Mars

In the paper

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

What the sources say

• ?Could 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)

  cites Freissinet et al., 2015 sourceExperimental — accuracy not yet measured

In the paper

“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.”

What the sources say

• Supported

  Section 3.5 reports that the Mg proportion in mixed Fe–Ca–Mg carbonate increased from 25°C to 70°C; a paired comparison also produced magnesian siderite at 25°C but ferroan magnesite at 70°C. This supports the experimental result attributed to Romanek et al. The Mars interpretation is framed as the citing authors’ inference, not as a finding attributed to the source. (LLM, conf=0.91)

  cites Romanek et al., 2009 source

In the paper

“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.”

What the sources say

• Supported

  Split into 2 atoms — 2 confirmed, 0 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

  cites Ehlmann and Edwards, 2014 source

In the paper

“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].”

What the sources say

• ?Not matched

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

  cites Bishop et al., 2013c
• ?Not matched

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

  cites Morris et al., 2010a

In the paper

“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).”

In the paper

“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.”

In the paper

“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.”

In the paper

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

In the paper

“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).”

In the paper

“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].”

What the sources say

• ?Not matched

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

  cites Bishop et al., 2015

In the paper

“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).”

In the paper

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

In the paper

“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.”

In the paper

“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).”

What the sources say

• ?Not checked — no full text of the sourcecites Wray et al., 2009 source

In the paper

“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.”

In the paper

“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.”

In the paper

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

In the paper

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

In the paper

“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)”

In the paper

“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”

In the paper

“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).”

In the paper

“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”

In the paper

“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).”

In the paper

“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).”

In the paper

“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.”

In the paper

“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).”

In the paper

“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.”

In the paper

“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.”

In the paper

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

In the paper

“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).”

In the paper

“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.”

In the paper

“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.”

In the paper

“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].”

What the sources say

• ?Not matched

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

  cites Hörz et al., 2015
• ?Not checked — no full text of the sourcecites Peel and Fassett, 2013 source

In the paper

“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.”

In the paper

“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].”

What the sources say

• ?Not matched

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

  cites Morris et al., 2010b

In the paper

“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.”

In the paper

“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.”

In the paper

“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.”

What the sources say

• ?Not checked — no full text of the sourcecites Chassefière et al., 2013 source
• ?Not checked — no full text of the sourcecites Lammer et al., 2013 source

In the paper

“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].”

What the sources say

• ?Not matched

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

  cites Bourke and Wray, 2011

In the paper

“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].”

What the sources say

• ?Not checked — no full text of the sourcecites Ruff et al., 2001 source
• ?Not matched

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

  cites Stockstill et al., 2005
• ?Not checked — no full text of the sourcecites Squyres et al., 2004 source

In the paper

“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].”

What the sources say

• ?Not matched

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

  cites Bishop et al., 2013b

In the paper

“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].”

What the sources say

• ?Not matched

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

  cites Carrozzo et al., 2013
• ?Not checked — no full text of the sourcecites Gilmore et al., 2014
• ?Not checked — no full text of the sourcecites Jain and Chauhan, 2015 source

In the paper

“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”

In the paper

“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].”

What the sources say

• ?Not checked — no full text of the sourcecites Alzate and Barlow, 2011 source
• ?Not checked — no full text of the sourcecites Bray et al., 2012 source
• ?Not checked — no full text of the sourcecites Tornabene et al., 2012 source

In the paper

“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].”

What the sources say

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

In the paper

“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].”

What the sources say

• ?Not checked — no full text of the sourcecites O'Connor, 1968 source
• ?Not checked — no full text of the sourcecites Goldspiel and Squyres, 1991 source

In the paper

“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].”

What the sources say

• ?Not checked — no full text of the sourcecites Kirkland et al., 2003 source
• ?Not checked — no full text of the sourcecites Edwards and Ehlmann, 2015 source

In the paper

“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.,”

What the sources say

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

In the paper

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

In the paper

“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.”

In the paper

“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.”

What the sources say

• ?Not checked — no full text of the sourcecites Michalski and Niles, 2010 source

In the paper

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

What the sources say

• ?Not checked — no full text of the sourcecites Kral et al., 2014 source

In the paper

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

In the paper

“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].”

What the sources say

• ?Not matched

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

  cites Hardie and Eugster, 1970
• ?Not checked — no full text of the sourcecites Tosca and McLennan, 2006 source

In the paper

“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].”

What the sources say

• ?Not checked — no full text of the sourcecites Milliken and Bish, 2010 source
• ?Not checked — no full text of the sourcecites Poulet et al., 2014 source

In the paper

“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].”

What the sources say

• ?Not matched

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

  cites Bishop et al., 2013b

In the paper

“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.”

What the sources say

• ?Not checked — no full text of the sourcecites Michalski and Niles, 2010 source

In the paper

“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.”

What the sources say

• ?Not checked — no full text of the sourcecites Bibring et al., 2006 source

In the paper

“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.”

In the paper

“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”

What the sources say

• ?Not checked — no full text of the sourcecites Edwards and Ehlmann, 2015 source
• ?Not matched

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

  cites Viviano-Beck, 2015

In the paper

“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].”

What the sources say

• ?Not checked — no full text of the sourcecites Ehlmann et al., 2008 source
• ?Not matched

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

  cites Bishop et al., 2013a
• ?Not matched

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

  cites Murchie et al., 2009a

In the paper

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