CLASSIFICATION AND ANALYSES OF MARE BOREUM ICECAP FROM CRISM OBSERVATIONS.

Introduction: Martian Polar Ice caps reveal large deposits of water-ice in North Pole and buried deposits of carbon-di-oxide ice in South Pole [1]. The spectral measurements of Martian Polar Ice caps from MRO-CRISM (0.370-3.290µm) on Mars Reconnaissance orbiter were used for the extended classification of different ice forms, derivation of ice indices, water to dust ratio and water equivalent of ice in Mare Boreum. Also, thermal inertia data from Viking Infrared Thermal Mapper was used to determine grain size of the classified ice forms. Background and Rationale: Christian Huygens in 1659 first reported the dark albedo features in Syrtis Major Region of Mars and in 1666 Giovanni Cassini noticed the bright markings in the Polar Region [2]. Although many attempts have been made to understand the dark layered deposits in terms of carbon-di-oxide cycle and water to dust ratio in Martian Polar Caps, the results are still retrospective. The following sections will present the results from our spectroscopic analyses of CRISM data. Water-ice and CO 2 -ice Spectra: The water-ice spectra shows distinct absorption features near 1.3 µm, 1.5µm and 2µm. The absorptions features for CO 2 -ice were found near 1.3µm, 1.4µm, 1.5µm and 2µm. The difference between water-ice and CO 2 -ice occurs near 1.4-1.5 µm. The doublet which is found in case of CO 2 -ice is absent in water-ice. It is clear that there exists a mixture of CO 2 -ice and water-ice in CRISM’s resolution of 200m. Difference is also seen in other properties like band depth, band area etc. that differ from one form to the other form. It was found from the band depths that when the dust is mixed with water-ice, the absorption feature is reduced by 0.42%. But when dust is mixed with CO 2 -ice, the absorption feature of CO 2 -ice is reduced by 0.55%. Thus the spectral absorption of water-ice is relatively resistant to band depth changes when mixed with dust. Figure 1. Water-Ice spectrum from CRISM.