Extraterrestrial and terrestrial outdoor applications of Mössbauer spectroscopy [Elektronische Ressource] / Paulo Antônio de Souza Júnior

Sujets

• Physik

Informations

• Publié par: johannes_gutenberg-universitat_mainz
• Publié le: 01 janvier 2004
• Nombre de lectures: 14
• Langue: English
• Poids de l'ouvrage: 16 Mo

Extrait

Extraterrestrial and Terrestrial Outdoor
Applications of M ossbauer Spectroscopy
Dissertation
zur Erlangung des Grades
des Doktors der Naturwissenschaften
(Dr. rer. nat.)
am Fachbereich Physik
der Johannes Gutenberg - Universit at
in Mainz
Paulo Antˆonio de Souza Junior´
geboren in Campo Grande
Brasilien
Referent: Prof. Dr. Dr. h.c. Philipp Gutlic? h
Koreferent: Prof. Dr. Hermann Adrian
Mainz 2004”Die Erfahrung nutzt erst der Wissenschaft sodann schodet sie,
weil die Gesetz und Ausnahme gewahr werdenaßt.l
Der Durchschnitt von beiden gibt keineswegs das Wahre.”
”The experience benefits science at first, then acts damaging
towards it, because the experience lets one become aware of law
and exception. The average of both is by no means the truth.”
[Goethe: Wilhelm Meisters Wanderjahre]To my parents Rose and PauloContents
1 Introduction 1
572 Fe M ossbauer spectroscopy 5
2.1 M effect . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2 M ossbauer experiment . . . . . . . . . . . . . . . . . . . . . . 9
2.2.1 Doppler effect . . . . . . . . . . . . . . . . . . . . . . . 9
2.2.2 The standard M ossbauer spectrometer . . . . . . . . . 10
2.2.3 The M ossbauer source . . . . . . . . . . . . . . . . . . 13
2.3 Important effects and transitions . . . . . . . . . . . . . . . . 14
2.3.1 Cosine smearing effect . . . . . . . . . . . . . . . . . . 14
2.3.2 Goldanskii-Karyagin effect . . . . . . . . . . . . . . . . 14
2.3.3 Super-paramagnetism. . . . . . . . . . . . . . . . . . . 15
2.3.4 Morin transition . . . . . . . . . . . . . . . . . . . . . 16
2.3.5 Verwey . . . . . . . . . . . . . . . . . . . . . 16
3 Miniaturized M ossbauer spectrometer 19
3.1 MIMOS II sensor head . . . . . . . . . . . . . . . . . . . . . . 20
3.2 M ossbauer sources, shielding, and collimator . . . . . . . . . . 24
3.3 Drive system . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.4 Detector system and electronics . . . . . . . . . . . . . . . . . 26
3.5 Temperature measurement . . . . . . . . . . . . . . . . . . . . 27
3.6 Operation modes and software . . . . . . . . . . . . . . . . . . 27
3.6.1 Data structure of MIMOS II . . . . . . . . . . . . . . . 29
3.7 MIMOS II calibration . . . . . . . . . . . . . . . . . . . . . . 29
3.7.1 Energy . . . . . . . . . . . . . . . . . . . . 31
3.7.2 Velocity calibration . . . . . . . . . . . . . . . . . . . . 32
3.7.3 Internal sample . . . . . . . . . . . . . . . . 33
3.7.4 FIDO trials . . . . . . . . . . . . . . . . . . . . . . . . 35
3.7.5 Health checks . . . . . . . . . . . . . . . . . . . . . . . 37
iiiiv CONTENTS
4 Analysis of the M ossbauer spectrum 39
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
4.2 Classical curve fitting . . . . . . . . . . . . . . . . . . . . . . . 40
4.3 Curve fitting using genetic algorithm . . . . . . . . . . . . . . 44
4.4 Fitting control using fuzzy logic . . . . . . . . . . . . . . . . . 47
4.5 M ossbauer-mineral data bank . . . . . . . . . . . . . . . . . . 49
4.6 M ossbauer phase identification . . . . . . . . . . . . . . . . . . 51
4.6.1 Neural identifiers . . . . . . . . . . . . . . . . . . . . . 54
4.6.2 The implemented neural network . . . . . . . . . . . . 56
4.6.3 Neural identification of minerals . . . . . . . . . . . . . 59
4.6.4 iden of crystalline structures . . . . . . 60
4.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
5 Selected terrestrial outdoor applications 65
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
5.2 Air pollution investigation . . . . . . . . . . . . . . . . . . . . 65
5.3 Historical artifacts analysis . . . . . . . . . . . . . . . . . . . . 69
5.3.1 Iron purity and corrosion . . . . . . . . . . . . . . . . . 70
5.3.2 Were iron artifacts burned in sacrifices? . . . . . . . . . 81
5.3.3 Identification of fragments . . . . . . . . . . . . . . . . 84
5.3.4 Pigment characterization . . . . . . . . . . . . . . . . . 88
6 Extraterrestrial applications 97
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
6.2 Meteorites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
6.2.1 Metallic meteorites . . . . . . . . . . . . . . . . . . . . 100
6.2.2 Chondrite . . . . . . . . . . . . . . . . . . . 101
6.2.3 Martian meteorites . . . . . . . . . . . . . . . . . . . . 103
6.3 Martian mineralogy . . . . . . . . . . . . . . . . . . . . . . . . 105
6.3.1 PublishedM ossbauerparametersonMarsanaloguemin-
erals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
6.4 M ossbauer experiments on Mars . . . . . . . . . . . . . . . . . 108
6.4.1 MIMOS II calibrations taken on Mars. . . . . . . . . . 109
6.4.2 In situ experiments on a Martian rock and soils . . . . 112
6.4.3 Strategy of M ossbauer data analysis. . . . . . . . . . . 113
6.4.4 Selected M results from Mars . . . . . . . . . . 115
7 Summary, conclusions and outlook 125
7.1 Summary of results . . . . . . . . . . . . . . . . . . . . . . . . 125
7.2 Conclusions and outlook . . . . . . . . . . . . . . . . . . . . . 127CONTENTS v
A Possible Mars analogue Fe-minerals 141
A.1 Oxide, hydroxide and oxide-hydroxide . . . . . . . . . . . . . . 143
A.2 Carbonates and Rich-Mn minerals . . . . . . . . . . . . . . . . 143
A.3 Sulphate, sulphide and sulphite . . . . . . . . . . . . . . . . . 144
A.4 Phosphates . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
A.5 Silicates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
A.5.1 Nesosilicates . . . . . . . . . . . . . . . . . . . . . . . . 147
A.5.2 Sorosilicates . . . . . . . . . . . . . . . . . . . . . . . . 148
A.5.3 Cyclosilicate . . . . . . . . . . . . . . . . . . . . . . . . 148
A.5.4 Inosilicates. . . . . . . . . . . . . . . . . . . . . . . . . 149
A.5.5 Phyllosilicates . . . . . . . . . . . . . . . . . . . . . . . 150
A.5.6 Tectosilicates . . . . . . . . . . . . . . . . . . . . . . . 152
A.6 Other minerals . . . . . . . . . . . . . . . . . . . . . . . . . . 152vi CONTENTSChapter 1
Introduction
Many efforts have started in the early nineties at the Technical University of
DarmstadtbyProfessorDr. EgbertKankeleitandhisco-workerstominiatur-
izealaboratoryM ossbauerspectrometersuchthatitcanbeusedforoutdoor
and extraterrestrial applications. These efforts continued since 1998 at the
Institute of Inorganic and Analytical Chemistry of the University of Mainz
with Dr. G ostar Klingelh ofer and co-workers. The miniaturized M ossbauer
spectrometer called MIMOS II has been recently proven to be a mobile tool
for the in situ characterization of samples and solving problems of mineral-
ogy, archaeology and so on.
One part of this thesis is devoted to the non-destructive analysis of the
surface of archaeological artifacts. Also, as an outdoor application, a field
experiment on air pollution characterization done in Brazil is presented.
The other part will deal with the presently on going experiments on Mars
performed by the rover Spirit of the Mars Exploration Rover mission from
NASA.TheMIMOSIIarebeingusedforthecharacterizationofiron-bearing
minerals in this extraterrestrial mission to Mars. The genesis of the plane-
tary surface can be assessed knowing its mineral composition; and to try to
get answers of some appealing questions: - Was Mars once a wet planet? -
Could it sustain life?
Life on Earth can thrive in many environments, everywhere with avail-
able liquid water, energy and nutrient sources. Mars could once hold such
environment. Yet, the evolution of both planets have diverged: Earth has
remainedwarmandwet, whileMarshasbecomecoldanddry. However, still
these are open questions as how wet and warm was Mars, and wether did
lifedevelopinourneighborplanet. Thesequestionshavebeengrowinginin-
terest since the controversial evidence for fossil microbial life in the Martian
12 CHAPTER 1. INTRODUCTION
meteorite ALH84001. Magnetite crystals in Martian meteorite ALH84001
are the focus of controversy about the possibility of past (and present) life
on Mars. McKay et al. [Mck 96] suggested that some magnetite crystals
associated with carbonate globules in the meteorite are biogenic because
they share many characteristics with magnetosomes from terrestrial magne-
1totactic bacteria. These characteristics include size consistent with single
magneticdomains,absenceofcrystallinedefects,chemicalpurity,andcoexis-
tencewithmetastablephasesinapparentdisequilibrium. Ontheotherhand,
Golden et al. [Gol 04] demonstrated that an abiotic inorganic history can
produce magnetite crystals like those in ALH84001 which does not support
an exclusively biogenic origin. This evidence still controversial. Wherever
life conditions hold, organisms will spring up and spread over. Live forms
willalwaysbestrugglingforwaystosurvive,toadaptandtoflourisharound.
Mars missions are focused to grow our understanding of the origin and
evolution of life in the solar system, determining what conditions were on
2early Mars, and whether the red planet supported life. Our best present
knowledge on Mars suggests that possible past life (fossils) would lie in for-
merly water-rich regions of ancient terrain or sediment deposits of earlier
terrain. But yet, the fundamental substance known to form life is still to
be geologically proven that once existed on Mars. Sinc