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LITHOLOGIC UNIT MAPPING BASED ON OMEGA/MARS EXPRESS DATA
Minqiang Zhu 3, * , Hongjie Xie b , Huade Guan c , Guanglu Zhu d
a Digital Land Key Lab of Jiangxi, East China Institute of Technology, Fuzhou, Jiangxi 344000, China -
mqzhu @ecit.edu. cn
b Earth & Environmental Science, University of Texas at San Antonio, TX 78249, USA - Hongjie.Xie@utsa.edu
c School of Chemistry, Physics and Earth Sciences, Flinders University of South Australia, GPO Box 2100, Adelaide,
Australia - Huade.Guan@flinders.edu.au
d Special Class for the Gifted Young (0600), University of Science and Technology of China, Hefei, Anhui 230026,
China - Zhugl@mail.ustc.edu.cn
Commission VI, WG VI/7
KEY WORDS: Mars, OMEGA/Mars Express, Lithologic Unit, Mapping, Minimum Noise Fraction
ABSTRACT:
This paper develops a procedure for mapping Martian lithologic units, using the OMEGA/Mars Express data. The procedure consists
of correcting Martian atmospheric absorptions based on an empirical transmission function method, noise-free principle components
analysis based on a minimum noise fraction (MNF) method, lithologic unit delineation, and spectral matching of the units to spectral
libraries using spectral feature fitting (SFF) and spectral angle mapper (SAM) methods. Two areas, Meridiani Planum and Ophir-
Candor Chasma for their mostly-known lithologic and chemical compositions, were chosen for testing the approach. It is found that
the MNF band 1 (accounting for ~50% of total information from 114 bands between 0.926 to 2.55 pm) is mostly correlated
(positively or negatively) to the albedo (correlation coefficient r up to 0.83 - 0.98) of the OMEGA imagery, while the MNF bands 2,
3, and 4 contain most lithological information for making an informative and useful geologic unit map. The two spectral matching
methods (SFF and SAM) emphasize different criteria and should be used together to achieve confident results.
1. INTRODUCTION
Existing Martian geologic map and its geologic units were
based on their geomorphology, crater features and density,
albedo, multi-spectral properties, and thermal characteristics
(USGS. 1986 and 1987). It was the best geologic map though it
was no way to tell really what minerals and lithologies for each
unit. Since January 2004, Europe Space Agency’s (ESA) Mars
Express satellite has been successfully operated for two Martian
years of data acquisition. OMEGA imaging spectrometer, one
of the sensors on board Mars Express, has revealed a diverse
and complex Martian surface mineralogy and composition
(Bibring et al. 2005). OMEGA/Mars Express imagery can be
used to map not only individual minerals, but also
corresponding lithologic units. The result will provide better
information on the Marian crustal composition and evolution.
The purpose of this study is to develop a procedure that can be
used to delineate the lithologic units based on the OMEGA
imagery. Two study areas, Meridiani Planum and Ophir-Candor
Chasma, were chosen to test our methods, since many previous
works based on TES, THEMIS, OMEGA, or Opportunity
Rover have been carried out in these two areas. This procedure
would make it possible to produce a new globe Martian
geologic map by merging the lithologic unit maps derived from
individual OMEGA orbit imagery.
2. DATASET
OMEGA onboard Mars Express provides unprecedented
mineral and lithologic information in 352 bands with a spatial
resolution of 300 m/pixel to 4 km/pixel and spectral resolution
of 7 nm in the visible and near-infrared range of 0.364 - 1.070
pm, 13 nm in infrared range of 0.926 - 2.695 pm, and 20 nm in
infrared range of 2.527 - 5.089 pm (Bibring, J.P., et al. 2005).
The spectral range and resolution allow the identification of
major surface and atmospheric species by their diagnostic
spectral absorption feature. The OMEGA data (ORB0529 3
and ORB548 3) for the two areas (Meridiani Planum and
Ophir-Candor Chasma) were downloaded from ESA’s
Planetary Science Archive. In this study, we mainly examined
the spectral range between 0.926 to 2.55 pm (114 bands), which
includes the diagnostic spectral absorption feature of minerals
and lithologies. The data was pre-processed using a modified
IDL program initially provided by ESA to a relative
reflectance image (I/F).
3. MAPPING PROCEDURE
3.1 Atmospheric correction
Atmospheric correction is required for the OMEGA data before
it is used to identify surface minerals, rocks and other materials.
Compare to Earth atmosphere, Mars has a very thin atmosphere
(0.006 bar) which is principally composed of C0 2 (95.3% by
volume). The atmospheric effect on the OMEGA imagery is
Minqiang Zhu. Digital Land Key Lab of Jiangxi, East China Institute of Technology, 56# Xuefu Road, Fuzhou, Jiangxi 344000,
China. E-mail: mqzhu @ecit.edu. cn.
