Investigating the mineralogy at Libya Montes, Mars, determining if carbonates are present, and characterizing the geologic history of the Isidis Planitia region

Grant #: NNX12AO55G
Senior Scientist: Janice Bishop

Objectives: We propose to investigate the phyllosilicate-bearing outcrops in the Libya Montes region, confirm whether or not carbonates are present, and characterize the geologic relationship between the aqueous units and mafic rocks. One challenge to detection of carbonates on Mars is that a number of Fe-bearing phyllosilicates also have a band near 2.3 µm. Our preliminary study of the spectral properties of nontronite-magnesite mixtures showed that the carbonate 2.3 µm band may be overshadowed by the nontronite band under certain conditions. In order to better understand the spectral properties of carbonates in mixtures, we propose to prepare several new carbonate mixtures and evaluate them using reflectance and Mössbauer spectroscopy and XRD. We will then use the VNIR results of the carbonate-phyllosilicate mixtures to resolve whether or not carbonates are present at Libya Montes. This project requires coordinated data analysis and laboratory investigations that are uniquely supported by PGG, and not by other NASA Mars research programs. 

Summary of Research Tasks: Our project includes five coordinated tasks designed to investigate the composition, character and stratigraphy of the aqueous mineralogy at Libya Montes and revise our understanding of the valley networks along the southern edge of Isidis Basin and the dominant geologic processes that have governed the Isidis Planitia region: 

1) Hyperspectral analyses of the Libya Montes region with CRISM data in order to uniquely identify the minerals present, 

2) Geologic analyses of the Libya Montes region with HRSC image data and DTMs, and CTX image data to gain morphological and stratigraphic information on a broad scale and with HiRISE image data and DTMs to gain morphological and textural information on a finer scale, 

3) Preparation of mixtures of carbonate and phyllosilicate minerals in the lab and characterization with VNIR, MB and XRD, 

4) Spectral analyses of the mixture data including quantitative band depth characterizations and Gaussian modeling compared to quantitative mineral abundance determinations from XRD and Mössbauer spectroscopy, 

5) Coordinated synthesis and analyses of the data in order i) to confirm (or possibly refute) the presence of carbonate at Libya Montes, ii) to determine the likely type(s) of carbonate minerals present, iii) to constrain the likely abundances of the carbonate and other minerals present, iv) to characterize the stratigraphy and assign relative ages of the aqueous units (e.g. carbonates older or younger or co-evolved with phyllosilicates and olivine?), and v) to determine what relationships there are between carbonates (if present) and other lithologies in the region. 

Expected Significance: Libya Montes is one of only a few places on Mars exhibiting carbonate and phyllosilicate signatures. These two minerals together are strong indicators of neutral waters. Understanding the nature of the aqueous deposits at Libya Montes has potentially far-reaching applications for the greater Isidis Basin region. If similar processes formed phyllosilicates and carbonates at Nili Fossae and Libya Montes then these processes could be very widespread in the ancient rocks across the Isidis region. This study could reveal that carbonates are more prevalent on Mars than realized to date.