Chemistry Reference
In-Depth Information
Fig. 2.48 First Mössbauer
spectrum recorded on the
Martian surface at Gusev
crater (17th January 2004,
measuring time 3 h 25 min).
The inset shows a view of the
Rover and of the MIMOS
spectrometer operating on
Mars [
84
,
85
]
Fig. 2.49 ''Blueberry''-like
spherules found in Meridiani
Planum on Mars surface were
analyzed by Mössbauer
spectroscopy and found to be
enriched in haematite, a-
Fe
2
O
3
[
86
,
87
]
The first Mössbauer spectrum recorded on the surface of Mars was obtained in
the Columbia Hills of Gusev Crater [
83
] close to the Rover landing site
(Fig.
2.48
). It clearly revealed Fe
II
containing species (olivine and pyroxene) as
well as some Fe
III
species, not yet identified at that stage. The discovery of olivine,
commonly found in lava on earth, was quite informative since this mineral is
known to weather to clays and iron oxides in the presence of water [
84
,
85
].
Nests with bluish mineral spherules similar to blueberries [
86
,
87
] (Fig.
2.49
)
were discovered in a region near the landing site of the Rover Opportunity in
Meridiani Planum [
88
,
89
]. Mössbauer spectra were recorded in places with and
without such 'Blueberry' spherules. The 'blueberries' minerals were found to be
enriched in haematite (a-Fe
2
O
3
).
One of the major discoveries of the MER mission was the identification of the
mineral jarosite by Mössbauer spectroscopy in S-rich, layered outcrop rocks at
Meridiani Planum [
90
] (Fig.
2.50
). Jarosite is a ferric sulphate hydroxide whose
generalized formula can be written (K,Na,H
3
O)(Fe
3-x
Al
x
)(SO
4
)
2
(OH)
6
, where
x \ 1. The end members KFe
3
(SO
4
)
2
(OH)
6
, NaFe
3
(SO
4
)
2
(OH)
6
, and (H
3
O)Fe
3
(-
SO
4
)
2
(OH)
6
are jarosite, natrojarosite, and hydronium jarosite, respectively. For
