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Laboratory
for ChemoMetrics,
Vienna (Austria) COSIMA |
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Aims of the Project |
Summary
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COSIMA stands for Cometary Secondary Ion Mass Analyzer. COSIMA is a
time-of-flight mass spectrometer (TOF) for secondary ion mass spectrometry
(SIMS). COSIMA
is one of the instruments of the ESA space mission
ROSETTA to comet Wirtanen.
COSIMA is dedicated to
collect and analyze cometary grains in situ
and to determine their organic and inorganic
components. |
The intimate
mixture of organic and inorganic material in cometary grains is considered to
has been essential – after impact on Earth – in the development of
self-reproducing molecules and the start of life. A prominent objective of COSIMA therefore is the search
for organic chemical precursor molecules in cometary grains; for instance
unsaturated nitrogen-containing compounds are expected. |
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In the Project MS-Chemometrics-COSIMA methods
are developed and tested for on board data evaluation and for mass spectral
data interpretation (see More Details). |
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[ Aims | People | Results | Presentations | Pictures | ROSETTA | COSIMA Instrument
| Comet
Wirtanen | Literature
] |
Last update 2000-12-04 |
More Details
The only mass spectrometric data on cometary dust
particles available to date, come from the dust impact mass spectrometers PIA
and PUMA on the GIOTTO and VEGA spacecrafts, respectively, that encountered
comet Halley.
Since then it is known that each particle is an
intimate mixture of a mineral core and ice, and simple as well as complex
organic molecules. Because the impact velocity in theses experiments was large
(> 60 km/s) mostly atomic ions were formed and analyzed in the Halley case.
However, evidence was found for the chemical nature
of the organic cometary material. Not a few well known molecules constitute the
cometary organics, but rather several chemical classes, each being represented by
a large number of individual substances. Most probable substance classes are highly
unsaturated compounds containing nitrogen and oxygen atoms.
It is considered that intimate mixtures
of organic and inorganic material in cometary grains have been essential -
after impact on earth - in the development of self-reproducing molecules and
even self-reproducing systems.
The space mission ROSETTA of
the European Space Agency (ESA) is planned to rendezvous with comet
46/p/Wirtanen. A set of instruments will land on the comet while the main part
of the space craft will remain in an orbit.
One of the instruments on
the orbiter will be COSIMA (Cometary
Secondary Ion Mass Analyzer). It is a time-of-flight mass spectrometer for
secondary ion mass spectrometry (TOF-SIMS) dedicated to collect and analyze
cometary grains in situ and to determine their organic and inorganic
components.
The experimental conditions
of COSIMA will require a pre-evaluation of data on board. Therefore the
applicability of chemometric methods (multivariate data analysis) for a
chemical structure-oriented interpretation of relevant mass spectrometric data
is investigated.
Because the COSIMA
instrument is still in a testing state reference compounds were measured by
plasma desorption mass spectrometry (PDMS).
Aims of
chemometrics were:
(1) exploratory
data analysis of potential spectra-structure relationships,
(2) development of
mathematical models for the prediction of substance classes and structural
properties, and
(3) development of
similarity criteria for PDMS (SIMS) spectra that well reflect structural
similarities.
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[ Aims | People | Results | Presentations | Pictures | ROSETTA | COSIMA Instrument
| Comet
Wirtanen | Literature
] |
Last update 2000-12-03 |
