• Ajai

      Articles written in Journal of Earth System Science

    • Detection of Mg spinel lithologies on central peak of crater Theophilus using Moon Mineralogy Mapper (M3) data from Chandrayaan-1

      D Lal P Chauhan R D Shah S Bhattacharya Ajai A S Kiran Kumar

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      Spectral reflectance data derived from Moon Mineralogy Mapper (M3) onboard India’s Chandrayaan-1 has revealed Fe bearing Mg-spinel-rich lithology on central peaks of the crater Theophilus. These newly identified Fe bearing Mg-spinel-rich rock types are defined by their strong 2-𝜇m absorption and lack of 1-𝜇m absorptions in spectral reflectance response. Such lithology has been reported previously along the inner ring of Moscoviense Basin on the lunar far side. The Modified Gaussian Modeling (MGM) analysis of the Fe bearing Mg-spinel reflectance spectra has been done and the results of the analysis clearly bring out a strong spectral absorption at 1872 nm with no significant absortion around 1000 nm. The presence of spinel group of minerals in the Theophilus central peak and the fact that central peaks mostly represent uplifted mass of deep crustal material confirm that central peaks can be used as a window to study the deep crustal and/or upper mantle composition and may lead to a fresh perspective about the crustal composition of Moon.

    • Morphometric and rheological study of lunar domes of Marius Hills volcanic complex region using Chandrayaan-1 and recent datasets

      A S Arya R P Rajasekhar Koyel Sur B Gopala Krishna K Suresh T P Srinivasan K V Iyer P Chauhan Ajai A S Kiran Kumar A D Pandey A Khare P K Verma

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      Marius Hills volcanic complex is one of the most important regions on the lunar surface having an abundant number of volcanic features like domes and cones. Systematic mapping of 106 domes/cones in theMarius Hills region was carried out in this study using high-resolution orthoimage and digital elevation models of Chandrayaan-1 and Kaguya missions. Various morphometric parameters like diameter, height, volume, flank slope, circularity index and form factor are derived for all the mapped domes. The rheological parameters, such as viscosity and eruption rate are estimated for isolated domes and cones superimposed over low domes. The morphometric and rheological properties of these domes arecomparable to those located in the area near to Hortensius crater and other mare regions. Surface ages derived for a selected region in NW portion of the Marius Hills volcanic complex using crater size frequency distribution technique yields ages of 2.98 and 1.91 Ga. It suggests that the domes in this region formed at about 2.98 Ga ago, and then, the younger mare basalts likely embayed this regionabout 1.98 Ga ago. Stratigraphic sequence of rilles, wrinkle ridge and domes shows that wrinkle ridges are the oldest, while the rilles are younger than the domes.

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