The use of the autonomous Xray diffraction

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The use of the autonomous X-ray diffraction
fluorescence instrument MARS-X
S.J. Van der Gaast4, R. Delhez1, A.D. Holland2,
I.B. Hutchinson2, N.H. Nelms2, I.L. Ten Kate3,
F.Westall, A.A. Wielders5 1 Laboratory of
Materials Science and Technology, Delft
University of Technology, Rotterdamseweg 137,
2628 AL Delft, The Netherlands 2 Space Research
Centre, Dept. Physics Astronomy, University of
Leicester, University Road, Leicester, LE1 7RH,
UK 3 Leiden Observatory, Leiden University, Niels
Bohrweg 2, 2333 CA Leiden, The Netherlands 4
Royal Netherlands Institute for Sea Research,
P.O. Box 59, 1790 AB Den Burg, The Netherlands 5
TNO-TPD Institute of Applied Physics,
Stieltjesweg 1, 2600 AD Delft, The Netherlands 6
Centre de Biophysique Moleculaire, Centre de
Biophysique Moleculaire, Rue Charles-Sadron 45071
Orleans cedex 2, France
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Goals

• Search for mineral deposits and structures that
  indicate formation by organisms
• Search for minerals that can host molecules of
  life on Mars
• Mineralogy of rocks, deposits and dust that helps
  interpretation of general geology of Mars

The mineralogy of the surface material of Mars
is the key to disclose its present and past life
and climates.
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The best tool is XRD/XRFWe propose the use of a
tandem XRD/XRF instrument

• Identification of a wide range minerals in
  complex mixtures
• Semi-quantitatively phase determination
• High resolution - large spacings - clay minerals
• lattice imperfection
• Crystallite sizes
• Average particle size lt 200Å

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Effective use

• Remote analysis by satellite
• find promising areas
• local mineral analysis by Mars-X
• minerals that can host molecules of life,
  bio-structures, general geology
• specific analysis of organic molecules
• detection of specific organic molecules (amino
  acids, bases, etc.) with e.g. GC/MS, HPLC

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Bio-generated structures

• Banded Iron formation (BIF) formed by algae
• alternating layers of Fe-(hydr)oxides and
  Al-Silicates
• Stromatolite formed by algae
• Ca-carbonates

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BIF Hamersley
Photo Jan Smit, Free Univ. Amsterdam
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BIF Hamersley
Photograph Jan Smit, Free University, Amsterdam
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Stromatolite shark bay, Australia
Photograph Frances Westall, CNRS, Orleans (Fr.)
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Minerals that can host organic molecules

• Clay minerals
• large internal surfaces of expanding clay
  minerals
• negatively charged
• Fe-(hydr)oxides
• large external surfaces

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Expanding clay minerals

• Smectite (montmorillonite)
• medium charge
• Vermiculite
• high charge

Absorption of positively charged organic
components, e.g. amino acids and bases on the
internal surfaces
Selection Protection
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Structure of smectite/vermiculite
a, b, hk0
9.15 Å
c, 00l
Si-O tetr.
Al-O oct.
11.5 Å - 0 RH empty 13 - 12.5 Å - 0 RH filled
Si-O tetr.
Isomorphous subst., e.g. Al for Si and Fe for Al
neg. charge
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Reflection XRD patterns of smectite (001)
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General Geology

• Mineralogy of unaltered basalt
• pyroxene, feldspar, mica, glass, olivine
• Weathering and erosion products
• palagonite, serpentine, nontronite
• Carbonates
• Hydrothermal products
• sulfates, chlorides
• Ice

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Conclusions

• Mineralogy provides the most reliable information
  for properly assessing the potential for
  capturing and preserving of a fossil record (J.D.
  Farmer, Fifth Int. Conf. on Mars)
• The proposed tandem XRD/XRF instrument Mars-X
  could be an optimum tool to achieve such
  information