SPS Seminar - Lunar elemental abundance estimation: A novel method based on Chandrayaan-2 CLASS and Chandrayaan-1 Moon Mineralogy Mapper datasets & Lunar Volcanism: The Tell-tale from a few Pre-Nectarian Basins

When:  Tuesday 15 November at 12pm

Where:  Microsoft Teams – Robert Hooke/Online

Speaker:  Dr Megha Bhatti - Planetary Sciences Division at PRL

Hosted by: Alexander Barrett/Mahesh Anand

Abstract:

The mapping of refractory elements at local and global scales is an important tool for revealing the petrological characteristics of the Moon and for understanding its geological evolution. The direct approaches (X-ray and Gamma ray spectroscopy) mainly provide elemental abundances at spatial resolution of tens of kilometers. In contrast, the indirect approaches (UV-VIS-NIR spectroscopy) provide spatial resolution of tens to hundreds of meters, but they are influenced by space-weathering and topographic effects and majorly based on empirical relationships between band parameters and the chemical composition of returned samples. We report the first employment of the Chandryaan-2 Large Area Soft X-ray Spectrometer (CLASS) data [1] from Chandrayaan-2 mission as ground truth to estimate FeO, Al2O3, and MgO for understanding the petrological characteristics of the Moon. The algorithm uses multivariate regression between CLASS derived elemental abundances from selected regions spread over mare and highlands and spectral parameters derived using the nearly global coverage of the Moon obtained by the Moon Mineralogy Mapper (M3) [2]. The same set of M3 spectral parameters have been used as proposed in [3] that is robust with respect to the effects of space weathering. The CLASS derived elemental abundances primarily rely on enhanced solar activity without any dependencies on empirical relationships to lunar returned samples and refer to the top most layer of regolith as M3. The M3 global reflectance mosaic is derived using the framework in [4]. The results will be discussed are based on a comparative analysis considering independent techniques [3, 5] applied on regional and global scales.

References: [1] Pillai N. S.et al. (2021) Icarus 363, 114436. [2] Pieters C. M. et al. (2009) Current Science 96, 500-505; [3] Bhatt M. et al. (2019) A&A 627, A155. [4] Wöhler, C. et al. (2017) Science Advances 3, e1701286. [5] Lucey P. G. et al. (2000) JGR 105, 20297-20306.

BIO:

Dr. Megha Bhatt is a faculty member in the Planetary Sciences Division at PRL. She obtained her Master’s degree in Electronics from India and PhD from the Max Plank Institute for Solar System Research, Germany. Her research is focused on understanding the evolution of our solar system by studying the surface composition of airless bodies. In particular, her interest lies in mapping the major lunar elements and mineral exposures at the top most layer of the Moon surface. Her major interest is in the spectrometric observations in the Visible-Near infrared wavelength range obtained from India’s. Chandrayaan missions. She is an active science team member of Chandrayaan-2 payloads; IIRS and CLASS and is actively involved in scientific discussions on landing site of India’s upcoming Moon missions. In addition to Moon surface composition studies, Dr. Bhatt also studied surface composition of asteroids Itokawa and Vesta, and Jupiter’s irregular satellites for establishing link between origin and subsequent geo-chemical evolutionary processes.
 

When:  Tuesday 15 November at 12;30pm

Where:  Microsoft Teams – Robert Hooke/Online

Speaker:  Dr Neeraj Srivastava - Planetary Sciences Division at PRL

Hosted by: Alexander Barrett/Mahesh Anand

Abstract:

Our understanding of the geology of the Moon has substantially improved from analysis of data from Kaguya, LRO, GRAIL, Chandrayaan-1, and Change’3-5 missions. New details about impact cratering, volcanism, and tectonism have emerged, requiring a fresh look at the existing evolutionary models. Revelations about recent volcanism on the Moon and new basin forming events during the pre-Nectarian times, when the crust was still evolving, are significant in this regard. Here, I will be presenting the results from our study of the geology of three pre-Nectarian aged impact basins Grimaldi (5.2° S, 68.6° W; ~400 km), Crüger-Sirsalis (16.0°S, 293.0°E; ~475 km), and Australe North (35.5°S, 96°E; ~880 km). Out of these three basins, the Grimaldi Basin is prominently manifested near the western boundary of the PKT, between the Oceanus Procellarum and the Orientale Basin; however, the other two lack any prominent topographic signature and have been recently reported from GRAIL data. Geomorphology, spectral reflectance studies, and crater chronology have been carried out to decipher the geological evolution of these basins especially focusing on their volcanic and tectonic history. It has been found that all these three basins experienced unexpectedly prolonged volcanism. The volcanism continued up to ~1.7 Ga in the Australe North Basin, ~1.4 Ga in the Crüger-Sirsalis Basin, and ~700 Ma in the Grimaldi Basin. Also, evidence of Copernican aged tectonic features have been found in the Grimaldi Basin suggesting that the Moon is geologically active and has a much more complex evolution than previously understood.  

BIO:

Dr. Neeraj Srivastava is a Planetary Geologist, serving the Physical Research Laboratory (PRL), Ahmedabad, India, as Associate Professor and Head of the Planetary Remote Sensing Section (PRSS). Dr. Srivastava received Ph.D. from IIT, Roorkee, India, in 2015. He initiated “Planetary Remote Sensing for Geological studies” in India in 2002 and contributed to the formulation of the Scientific Objectives of the Chandrayaan-1 mission. Dr. Srivastava has carried out research on various aspects of the geology of the Moon and Mars and is particularly known for his research works related to Recent Volcanism on the Moon. Dr. Srivastava is the recipient of the inaugural “COSPAR Outstanding Paper Award for Young Scientists – Scientific Commission B” in 2008 and LPI Career Development Award in 2013.