Quantitative Characterization of Lunar Mare Orientale Basalts Detected by Moon Mineralogical Mapper on Chandrayaan-1 - Planetary Exploration and Science: Recent Results and Advances - page 22

various basaltic spectra, chemistry and mineralogy have been employed to unmixing
analysis. Comparing the spectral profiles of the basaltic regions with the RELAB
basaltic spectra, the distribution and nature of TiO 2 basalts in the Orientale basaltic
regions have been analyzed in quantitative manner in the present research.

Keywords Mare Orientale ￿ Lacus Veris ￿ Lacus Autumni ￿ Spectral unmixing ￿
End-member

2.1 Introduction

The lunar mare basalts are concentrated on the near surface of the Moon. The low-
albedo smooth plains of lunar mare basalt covered almost 20 % of the lunar surface
(Head 1976 ). Right from the beginning of lunar observation, the distinction between
the lunar highlands and maria has been recognized (Taylor 1975 ). The 16 % of the
lunar surface is covered by about 23 lunar mares, most of which are located in the
near side of the Moon and the remaining three mares such as Mare Orientale, Mare
Moscoviense and Mare Ingenii are located in the far side of the Moon. The lunar
rock samples collected through Apollo and “Luna” series missions indicated that
the lunar mare materials are predominantly composed of basalts. The lunar surface
is mainly composed of plagioclase, pyroxene, olivine, ilmenite, agglutinitic and
volcanic glass. The mineralogical diversity of the mare basalts has been examined
through spectroscopy and linked to the surface units of returned samples (Pieters
1978 , 1993 ; Staid et al. 1996 ; Staid 2000 ; Lucey et al. 2006 ).
The major minerals among various types of mare basalt are pyroxene, Mg-rich
olivine, Ca-rich feldspar, and ilmenite (McCord et al. 1972 ). Lunar basalt samples
approximately consist of 51 % of pyroxene, 27 % plagioclase, 8 % olivine and
11 % opaques (Crown and Pieters 1987 ). In general, the Fe- and Mg-rich mare
regions contain abundant calcic pyroxenes and the Al-rich highlands contain low-
calcium pyroxenes; both exhibit diagnostic absorption features in the reflectance
spectral profile (Adams 1974 ). The dominant pyroxene in the mare basalt is high Ca-
clinopyroxene. Titanium is one of the major elements in mare rocks and accounts
for 0.5-13 %. Based on titanium content, the basalts can be divided into three
types: high-Ti basalts, low-Ti basalts, and high-Al, low-Ti basalts (Cloutis and
Gaffey 1991 ). Although a variety of distinct basalt types exist, pyroxene is the most
abundant mineral in these basalts, followed by plagioclase. The amount of olivine
and ilmenite in the basalts varies from minor to 20 % (Pieters and Englert 1997 ).
Hyperspectral remote sensing or imaging spectroscopy and reflectance spec-
troscopy are efficient tools to detect and quantify the mineral compositions on
Earth and planetary surfaces (Shkuratov et al. 2007 ;Chenetal. 2007 ; Pieters et al.
2008 ; Clark et al. 2008 ). Nowadays, although mineral species could be successfully
detected by hyperspectral data (Clark et al. 2003 ), the mineral abundance is difficult
to retrieve. Retrieval of mineral abundance is hindered by the complexities of
mixture characteristics of mineral spectra.