The Planet, Mars Lecture 9: In-situ characterization of the Martian surface by landers and rovers
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The Planet, Mars
Lecture 9: In-situ characterization
of the Martian surface
by landers and rovers
Antoine Pommerol, 24/11/2011
1
jeudi 24 novembre 2011
Last week
We have seen how infrared spectroscopy can be used to study the
mineralogical composition from the orbit
We have seen that aqueous alteration minerals, essentially phyllosilicates and
sulfates, attest for past interactions between rocks and minerals
Phyllosilicates indicate extensive alteration of the primordial Martian crust
during the Noachian area
Massive deposition of sulfates in Valles Marineris and a few other locations
during the Hesperian indicate a major change of the Martian environment
No obvious aqueous alteration during the Amazonian area. Slow formation
of quasi-amorphous iron oxides
A lot of remaining open questions: interbedded phyllosilicates and sulfates,
putative carbonates and chloride deposits...
2
jeudi 24 novembre 2011
This week
In situ analyses of the Martian soils by landers and rovers
Complement orbital studies
Ground truth
3
jeudi 24 novembre 2011
Outline
1. Landers and rovers on Mars
2. The chemical composition of the ground
3. In-situ mineralogic analyses
4. Physical properties of the soils
5. Chemical properties of the soils
4
jeudi 24 novembre 2011
Landed missions on Mars
Viking 1 (1976) Viking 2 (1976)
Mars Pathfinder (1997)
MER-A, Spirit (2004)
MER-B, Opportunity (2004) Phoenix (2008)
5
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Landed missions on Mars
6
jeudi 24 novembre 2011
Selection of landing sites
Based on orbital geomorphologic and mineralogic studies
Morphology and mineralogy can sometimes provide
contradicting indications...
7
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Chryse Planitia
Viking 1
Pathfinder
8
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Utopia Planitia
Viking 2
9
jeudi 24 novembre 2011
Gusev Crater
MER-A, Spirit
10
jeudi 24 novembre 2011Meridiani Planum
MER-B, Opportunity
11
jeudi 24 novembre 2011Meridiani Planum
12
jeudi 24 novembre 2011Green Valley
Phoenix
13
jeudi 24 novembre 2011Green Valley
14
jeudi 24 novembre 2011Outline
1. Landers and rovers on Mars
2. The chemical composition of the ground
3. In-situ mineralogic analyses
4. Physical properties of the soils
5. Chemical properties of the soils
15
jeudi 24 novembre 2011Principle of X-ray fluorescence
Atoms exposed to radiation with energy higher than their ionization
potential
Possibility of ejection of tightly held electrons from the inner orbitals
(K and L shells)
Filling of the inner orbitals by electrons from the outer orbitals
Falling electrons release part of their energy (difference of energy
between the atomic shells) as a X photon
The energy of these X photons depends on the nature of the core
Naming convention: L ➔ K = Kα, M ➔ K = Kβ, M ➔ L = Lα ...
16
jeudi 24 novembre 2011Principle of X-ray fluorescence
L shell
Emission of a
K shell photo-electron
Incident X photon
M shell
Emission of a
X photon: Kα
Emission of a
Emission of a X photon: Kβ
photon «Auger» X-ray
fluorescence
17
jeudi 24 novembre 2011Example of a X-ray fluorescence
spectrum
Se, Kα
Ar, Kα Cu, Kα
Zn, Kα
Fe, Kα
Counts
Cu, Kβ
Mn, Kα Fe, Kβ
Ti, Kα
Energy (keV)
18
jeudi 24 novembre 2011Example of a X-ray fluorescence
spectrum
19
jeudi 24 novembre 2011The APXS instruments
First instruments developed in the 60s at the University of Chicago for the
Lunar Surveyor landers
Further developments for the Russian Phobos missions, Mars-96. Collaboration
between Max Planck Institute (Germany), University of Chicago (USA),
University of Guelch (Canada)
Successfully used on the Mars Pathfinder and MERs
Installed on-board MSL
20
jeudi 24 novembre 2011Principle of α-particles backscattering
The Rutherford / Geiger-Marsden experiment (1909)
Transmission of α particles (+ charge) through a thin gold foil
Most of the particles are not deflected but a few particles are
deflected at high angle, up to 180°
Rutherford: «The greater part of the mass of the atom was
concentrated in a minute nucleus»
Strong central positive charge in less than 1/4000 the atom diameter
➔ Discovery of the atomic nucleus
➔ Planetary Model of the atom
21
jeudi 24 novembre 2011Principle of Rutherford backscattering
electron shell
α
α
nucleus
α
Elastic collisions between the α particles and the atom nucleus
Energy of the backscattered α particles ➔ mass of the nucleus
22
jeudi 24 novembre 2011The APXS instruments
MER version
Rieder et al. (2003)
23
jeudi 24 novembre 2011Results: the composition of the surface
Pathfinder vs.Viking 5 Pathfinder soils
Relative homogeneity of
soils around Mars
Rieder et al. (1997)
24
jeudi 24 novembre 2011Results: the composition of the soils
Relatively homogeneous across the planet
Essentially basaltic but with
high concentrations of iron, sulfur and chlorine
Rieder et al. (1997)
25
jeudi 24 novembre 2011Results: the composition of the surface
Pathfinder
Calculation of dust-free rock compositions
The composition of the rocks seems to be andesitic, close to the
average composition of the terrestrial crust!
(Feldspaths, Orthopyroxene, Quartz)
Spirit
Rock Abrasion Tool (RAT) to remove the surface coatings/dust
Basaltic composition of the rocks in the Gusev plains
and Opportunity? ➔ next section!
Rieder et al. (1997)
26
jeudi 24 novembre 2011Outline
1. Landers and rovers on Mars
2. The chemical composition of the ground
3. In-situ mineralogic analyses
4. Physical properties of the soils
5. Chemical properties of the soils
27
jeudi 24 novembre 2011The Mini-TES instrument
A miniaturized version of the orbital TES instrument (Lecture 8)
Modeling of minerals abundance
Selection of interesting samples and sites for detailed in-situ
investigations
28
jeudi 24 novembre 2011Principle of Mössbauer spectroscopy
Solid sample exposed to gamma radiations originating from a given
isotope of a given element.
MB spectroscopy is only sensitive to this isotope in the sample
If the emitting and absorbing nuclei are in identical environments,
most of absorptions - emissions occur with equal energy (recoil-free)
Differences of environment induce minor differences between the
energy emitted by the source and the energy absorbed by the sample
Mössbauer spectroscopy probes these tiny differences of energy by
slightly altering the energy of the source and looking for resonances
with the energy re-emitted by the sample
29
jeudi 24 novembre 2011Principle of Mössbauer spectroscopy
Practically, this is done by moving the source relative to the sample to
induce frequency change by Doppler effect.
The intensity of the energy transmitted or backscattered by the sample
plotted as a function of the speed of the source / sample movement is the
Mössbauer spectrum.
57Co ➔ 57Fe (excited) ➔ 57Fe (ground)
30
jeudi 24 novembre 2011The MER Mössbauer instrument
Klingelhöfer et al. (2003)
31
jeudi 24 novembre 2011The MER Mössbauer instrument
Klingelhöfer et al. (2003)
32
jeudi 24 novembre 2011Results at Gusev
Rocks in Gusev plains = basaltic composition
Fleischer et al. (2010)
33
jeudi 24 novembre 2011Results at Meridiani
34
jeudi 24 novembre 2011Results at Meridiani
35
jeudi 24 novembre 2011Results at Meridiani
36
jeudi 24 novembre 2011Results at Meridiani
37
jeudi 24 novembre 2011Mini-TES results
38 Christensen et al. (2004)
jeudi 24 novembre 2011Mini-TES results
39 Christensen et al. (2004)
jeudi 24 novembre 2011Endurance crater
40
jeudi 24 novembre 2011Victoria crater
41
jeudi 24 novembre 2011The plains jeudi 24 novembre 2011
The road to Endeavor crater
Total driving distance > 30 km
43
jeudi 24 novembre 2011Endeavor crater
Some phyllosilicates were identified by CRISM inside this crater (Wray et al., 2009).
Soon the first in-situ investigations of phyllosilicates-bearing rocks?
44
jeudi 24 novembre 2011Meridiani Planum as seen by Opportunity
The plains are covered by basaltic sand that form ripples shaped by the
winds
The hematite signature identified by TES is carried by hematitic
concretions
These concretions are weathered from layered sulfate-rich bedrocks
exposed by impact craters
Sedimentary features attest for both aeolian and aqueous depositions of
sediments
Post-deposition alteration by acidic aqueous processes
Hydrated minerals are observed on the ground
but were not detected from orbit
45 Arvidson et al. (2011)
jeudi 24 novembre 2011Gusev crater
46
jeudi 24 novembre 2011Traces of alteration in the Columbia hills
47
jeudi 24 novembre 2011Traces of alteration in the Columbia hills
Clovis rock
Goethite: FeO(OH)
48 Morris et al. (2008)
jeudi 24 novembre 2011Traces of alteration in the Columbia hills
amorphous silica (up to 90%!!)
ferric sulfates
Hydrothermal origin:
Interaction of rocks with
acidic water produced by
volcanic activity?
Hot spring environment?
Clovis rock
49 Ruff et al. (2011)
jeudi 24 novembre 2011Traces of alteration in the Columbia hills
Carbonate in the Comanche outcrop
16 - 34 wt. % Mg-Fe carbonate
Same composition as the carbonates
globules in the meteorite ALH84001
Clovis rock
50 Morris et al. (2010)
jeudi 24 novembre 2011Gusev crater as seen by Spirit
The plains of Gusev carters are covered by unaltered olivine-rich basaltic
material (rocks and soils).
The Columbia hills are older and were not covered by lava.
They display sporadic evidence for past aqueous alteration of rocks,
probably in hydrothermal environments (hydrovolcanism).
Alterations with low to high water-to-rock ratios and neutral to acidic
conditions
51 Arvidson et al. (2011)
jeudi 24 novembre 2011Outline
1. Landers and rovers on Mars
2. The chemical composition of the ground
3. In-situ mineralogic analyses
4. Physical properties of the soils
5. Chemical properties of the soils
52
jeudi 24 novembre 2011Phoenix
53
jeudi 24 novembre 2011The landscape at Phoenix landing site
54
jeudi 24 novembre 2011Phoenix
10 cm tall pile
8 cm wide trenches
55
jeudi 24 novembre 2011Phoenix
56
jeudi 24 novembre 2011Phoenix: First truly microscopic images
from the surface of Mars
Goetz et al. (2009)
500 µm
57
jeudi 24 novembre 2011Phoenix: First truly microscopic images
from the surface of Mars
Goetz et al. (2009)
500 µm 58
jeudi 24 novembre 2011Particle size distribution
Goetz et al. (2009)
59
jeudi 24 novembre 2011Microscope analysis of Phoenix soils:
Conclusions
Four types of particles:
(1) red fines (< 20 µm)
(2) brown sand (20 - 100 µm)
(3) black sand (20 - 100 µm)
(4) white fines (< 10 µm)
No large particles (> 200 µm)
Black sand = unweathered basaltic lithic fragments, rounded by aeolian transport
Red fines = global unit consisting of airborne dust + bright surface dust
Brown sand = from the ice-rich ground or altered volcanic material?
White fines = carbonates, perchlorates, feldspaths...???
Goetz et al. (2009)
60
jeudi 24 novembre 2011Phoenix Atomic Force Microscope
A Swiss AFM to
study the finest
dust particles
5 µm
61
jeudi 24 novembre 2011Outline
1. Landers and rovers on Mars
2. The chemical composition of the ground
3. In-situ mineralogic analyses
4. Physical properties of the soils
5. Chemical properties of the soils
62
jeudi 24 novembre 2011Chemistry of Phoenix soils
Phoenix
Wet Chemistry Laboratory
3.3 (±2) mM Mg2+
2.4 (±0.5) mM ClO4
1.4 (±0.3) mM Na+
0.6 (±0.3) mM Ca2+
0.5 (±0.1) mM Cl-
0.4 (±0.1) mM K+
Moderate pH of 7.7 (±0.3)
Presence of perchlorate salts that lower the melting point
of the ice
Kounaves et al. (2010)
63
jeudi 24 novembre 2011Gale Crater
MSL / Curiosity
64
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