Geochemistry of Carbonates on Mars: Implications for Climate History and Nature of Aqueous Environments

Abstract

Ongoing research on martian meteorites and a new set of observations of carbonate minerals provided by an unprecedented series of robotic missions to Mars in the past 15 years help define new constraints on the history of martian climate with important cross- cutting themes including: the CO 2 budget of Mars, the role of Mg-, Fe-rich fluids on Mars, and the interplay between carbonate formation and acidity.Carbonate minerals have now been identified in a wide range of localities on Mars as well as in several martian meteorites. The martian meteorites contain carbonates in low abundances (<1 vol.%) and with a wide range of chemistries. Carbonates have also been identified by remote sensing instruments on orbiting spacecraft in several surface locations as well as in low concentrations (2-5 wt.%) in the martian dust. The Spirit rover also identified an outcrop with 16 to 34 wt.% carbonate material in the Columbia Hills of Gusev Crater that strongly resembled the composition of carbonate found in martian meteorite ALH 84001. Finally, the Phoenix lander identified concentrations of 3-6 wt.% carbonate in the soils of the northern plains.The carbonates discovered to date do not clearly indicate the past presence of a dense Noachian atmosphere, but instead suggest localized hydrothermal aqueous environments with limited water availability that existed primarily in the early to mid-Noachian followed by low levels of carbonate formation from thin films of transient water from the late Noachian to the present. The prevalence of carbonate along with evidence for active carbonate precipitation suggests that a global acidic chemistry is unlikely and a more complex relationship between acidity and carbonate formation is present.

Low HesperianPCO2constrained from in situ mineralogical analysis at Gale Crater, Mars

“…This is well below threshold levels required to keep the average temperature of early Mars above 273 K for long periods in climate models, therefore either lacustrine features of Gale formed in a cold environment (37) or the problem of reconciling Mars' early climate with geological record of an active hydrosphere remains. Our results imply that the overall lack of carbonates found in the geological record of Mars (5,6,28,35) is a direct reflection of the composition of the ancient atmosphere. supported by the NASA Mars Exploration Program.…”

“…The widespread distribution of hydrous clay minerals in martian terrains of this age and their subsequent demise provide pivotal supporting evidence (3,4), but the clay mineral-bearing deposits also present a paradox in that carbonate minerals, expected coprecipitates in surficial settings in communication with a CO 2 -bearing atmosphere, are typically absent (5). Atmospheric reconstructions using carbon isotopic measurements and global inventories of martian carbon also indicate 100s mbar CO 2 levels (5,6). This leads to the question of how the surface of ancient Mars, faintly heated by a young sun, was kept warm enough to allow an active hydrological cycle, without substantial amounts of a key greenhouse gas in the atmosphere.…”

Dioctahedral Phyllosilicates Versus Zeolites and Carbonates Versus Zeolites Competitions as Constraints to Understanding Early Mars Alteration Conditions

“…To a lesser extent, non‐clay minerals associated with the Fe,Mg‐phyllosilicates were observed on the Noachian Martian surface, such as carbonates (Ehlmann et al, ; Niles et al, ; Wray et al, ) and zeolites (Carter et al, , see also section 2 of this paper). The presence of carbonates could be linked to an early thicker CO 2 ‐rich atmosphere (Morse & Marion, ), which allows for the presence of liquid water (e.g., Pollack et al, ).…”

Temperature Oscillation Modulated Self-Assembly of Periodic Concentric Layered Magnesium Carbonate Microparticles

“…It also plays an important role in biomineralization [26], [40]. Magnesium carbonate hydrates, present in different hydrated and basic forms including nesquehonite (MgCO 3 ⋅3H 2 O), lansfordite (MgCO 3 ⋅5H 2 O), hydromagnesite (Mg 5 (CO 3 ) 4 (OH) 2 ⋅4H 2 O) and artinite (Mg 2 CO 3 (OH) 2 ⋅3H 2 O), are of significance in sedimentary geology and planetology [41], [42], and extremely important to the geo-sequestration of atmospheric CO 2 [43], [44]. They have also been widely used for various industrial applications including pharmaceuticals and cosmetic manufacturing [45], [46].…”