Hyperspectral remote sensing is used to determine the inner composition of planetary surfaces. Sensors on spacecraft capture reflectance spectra that can be matched to characteristic curves for minerals. This reveals surface composition and allows inferences about geological history. Analysis of lunar data found evidence of volcanism and a magma ocean. Mars shows a primitive southern hemisphere versus a volcanically active northern one with signs of past water. Saturn's icy moons contain water ice and organics that provide clues about their formation. Hyperspectral remote sensing is a valuable tool for comparative planetary science.

1. HYPERSPECTRAL REMOTE SENSING OF
PLANETARY SURFACES: INNER
COMPOSITION OF THE PLANETS
By Bitopan Gogoi
CEaS 12384

2. PLANETARY REMOTE SENSING METHODS
• Earth based telescopes
• Flyby/orbiters around the
planetary bodies
• In situ probing by landers/rovers
• Direct inference-
• Surface features
• Topography
• Surface composition
• Indirect inference-
• Prevailing environment
• Inner composition
• Surface and plutonic processes
• Volcanic activities
• Age estimates etc.

3. REFLECTANCE SPECTROSCOPY AS A TOOL
• Spectral reflectance curves from different planetary bodies are obtained
using space shuttle mounted hyperspectral remote sensing sensors
• Not possible to obtain using Earth-based telescope
• Compared to known reflectance curves of common rock forming minerals
• Each mineral have its unique characteristic spectral reflectance curve, from
which the mineral can be identified
• Problems encountered-
• IFOV focus a mixture of compositions
• Space weathering leads to alteration, eg. Reddish tone because of Iron deposit around
minerals

4. CHARACTERISTIC REFLECTANCE CURVE FOR THE
PLANET FORMING MINERALS
Figure 1.
Reflectance
spectra of (a)
common rock
forming
minerals and
(b) water
bearing
minerals
formed in
Mars due to
alteration
(Viviano-Beck
et al.2)

5. ON BOARD HYPERSPECTRAL SPECTROSCOPIC SENSORS
Table 1. List of various missions carrying on board sensors for hyperspectral remote sensing (Chauhan et al.1.)

6. LUNAR REFLECTANCE SPECTROSCOPY: HYPERSPECTRAL RS
DISCOVERIES
• 1.3 μm absorption ⇒crystalline iron-bearing clear plagioclase ⇒ lunar
rocks originated from crystallization of a surface magma ocean
• Volcanic deposits (glass) ⇒ Evidence of volcanism in the past
• M3 data ⇒ A new rock type (Mg-Spinal Anorthosite) ⇒ Neo-volcanic
flow
• Materials in the center of craters ⇒ deep origin ⇒ Composition
beneath the crust
• Presence of hydrous mineral ⇒ rubbishes the pre-existing idea of dry
lunar crust

7. HYPERSPECTRAL REMOTE SENSING OF MARS
• Problems faced: CO2 rich atmosphere
• Surface composition of the planet
• Southern hemisphere – primitive crust, no alteration
• Northern hemisphere – upper crust formed due to volcanic activity
and sedimentation, lower crust is primitive
• Multiple glaciation event in the northern hemisphere
• Evidence of hydrous minerals and processes like – surface weathering,
ground water assisted weathering etc.

8. SATURN AND ITS MOONS
• Detail study of Saturn’s ring is undergoing since last 10 years, consists
of primarily water-ice
• Major satellites – Mimas, Enceraldus, Tethys, Dione, Rhea, Hyperion
Iapetus and Phobe under study – Predominantly icy objects
• Visible range spectroscopy – some coloring agent on the surfaces
• Iapetus – albedo contrast between two hemispheres. High albedo in
one hemisphere due to presence of ice, low albedo (dark) in other
hemisphere due to presence of hydrocarbons

9. REFERENCES
1. Chauhan, P., Kaur, P., Srivastava, N., Sinha, R. K., Jain, N., Murty, S. V. S., Hyperspectral remote
sensing of planetary surfaces: an insight into composition of inner planets and small bodies in
the solar system, Current Science, Vol. 108, No. 5, 10 March 2015
2. Viviano-Beck, C. E. et al., Revised CRISM spectral parameters and summary products based on
the currently detected mineral diversity on Mars. J. Geophys. Res. Planets, 2014, 119, 1403–
1431.
3. Hartmann, W. K., Moons and Planets, Wadsworth Publishing Company, 4th edn, 1999.
4. Cruikshank, D. P. et al. and the VIMS Team, Hydrocarbons on Saturn’s satellites Iapetus and
Phoebe. Icarus, 2008, 193, 334–343.
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