Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.cosmos.ru/conf/2009elw/presentations/presentations_pdf/session7/Wurz_ELW.pdf Дата изменения: Mon Mar 2 19:59:35 2009 Дата индексирования: Mon Apr 6 23:50:35 2009 Кодировка: Поисковые слова: mercury surface

In Situ Composition Analysis of Planetary Surfaces by Laser-Based Mass Spectrometry

Peter Wurz and Marek Tulej
Physikalisches Institut UniversitДt Bern, Sidlerstrasse 5, CH-3012 Switzerland

George Managadze
Space Research Institute (IKI), ul. Profsoyuznaya 84/32, Moscow, 117997, Russia


Introduction
Science Scope
-- Elemental composition of solids (soil, rock, ice) -- Derive the chemical composition and infer mineralogical composition -- Isotopic composition -- Bio markers, bio molecules -- Trace elements -- Toxic substances -- Context science
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Missions
-- Russian mission Phobos-Grunt to the Mars moon Phobos -- Exploration of the Jupiter system -- European mission to planet Mercury, BepiColombo

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Why Laser Ablation?
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Traditional solid sample ionization:
-- E.g. dissolution and inductively coupled plasma, glow-discharge, spark source, particle bombardment -- All require sample preparation and controlled gas pressure

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Laser ablation/ionisation couples well with TOF-MS
-- Low mass, size and power requirements -- Direct interface to mass analyzer -- Appropriate duty cycle

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Depth profiling possible Laser ablation/ionisation TOF-MS have been previously built for space:
-- LIMA-D on Phobos mission -- LASMA on Phobos-Grunt -- LAMS from APL, John Hopkins University
­ Still at prototype stage ­ Based on earlier IKI design

-- LMS for 21. Februar 2009

BepiColombo/MSE

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Focusing of Ablation Laser
Laser beam Depth of focus must be at least 100 m (±10% irradiance points) Regolith target, > Irradiance should ideally be grain size 10­ constant across the focus 100m, therefore > Require (1­4)·109 W/cm2 at rough on this scale. focus power (<108 W/cm2): Too little
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5%

severe elemental fractionation due to thermal effects, low yield, polyatomic interferences
>100m

Too much power (>1010 W/cm2): increased ion energy dispersion, high energy tail on peak shape, multiply charged ion interferences
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Possible Laser Implementation
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Passively Q-switched diode pumped microchip laser (Nd:YAG=1064nm)
-- typically 10 J,1 ns pulse for 10 kW peak power at 10 kHz repetition rate -- when focused to 20 m spot gives about 5 GW/cm2 0.1 m depth/pulse or 104 ions

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Beam delivery
-- -- -- -- Need high intensity Short focal length lens Must avoid deposits on lens Hollow optical fibre?

10mm

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Requires 1.85V, 1.4A (2.6W) 39mm
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Prototype of Laser Mass Spectrometer (LMS) for the Mercury Lander
Laser unit with electronics Ion mirror Thermal enclosure High-voltage electronics Detector unit Sampling point
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U. Rohner, J. Whitby, and P. Wurz, Meas. Sci. Technol., 14 (2003), 2159­2164.

160 mm

Prototype

Flight Design

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Rover LMS V 3.2 m
53 m

U. Rohner, J. Whitby, P. Wurz, and S. Barabash, Rev. Sci. Instr., 75(5), (2004), 1314­1322. 21. Februar 2009

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Cr/Fe/Ni Spectrum
52Cr 56

Fe

M/M 180
/ 54Fe
53Cr

54Cr

Fe
57

58

Ni / 58Fe

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Phobos-Grunt (rus. -)
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Collect soil samples from Phobos and possibly from Mars and return them to Earth for scientific analysis. Phobos, Mars, and Martian space investigations. In situ and remote studies of Phobos, including analysis of soil samples. Monitoring the atmospheric behaviour of Mars, including the dynamics of dust storms. Studies of the vicinity of Mars, to include its radiation environment and plasma and dust.

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Mars Express / ESA 12


Phobos-Grunt Structural Model

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LASMA PI: G.Managadze, IKI

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LASMA PI: G.Managadze, IKI

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LASMA Electronics

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Europa / Jupiter

Gallileo / NASA

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Europas Surface Composition
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Dark Areas (ice-poor regions)
--MgSO4 · xH20 --Na2SO4 · xH20 --Na2CO3 · xH20 --H2SO4 · xH20

Bright Areas (ice-rich regions)
--H20, CO2, --SO2, Sx, --H2O2, ...
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Possible extremophile bacteria
-- -- -- -- Cyanidium Deinococcus radiodurans Sulfolobus shibatae Escherichia coli

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Biomarker Definition and Examples
Category/Definition Category 1 ­ The property is indisputable evidence for life and has characteristics which cannot be produced by any known nonbiologic process either in nature or in the laboratory despite extensive attempts. Examples · Actual unambiguous living forms capable of metabolism, movement, and reproduction · Complex fossils such as trilobites or skeletons with indisputable morphologies (extremely difficult with single-cell life) · Hopanes (prokaryotic cell membrane residue)1 · Steranes (eukaryotic cell membrane residue)1 · Porphyrins (hemoglobin residue)1 · · · · · · · · · · · · · · ·
1 2

Category 2 ­ The property is very strong evidence for life and is not likely to be produced by known nonbiologic processes, but is not indisputable. Category 3 ­ The property is known to be produced by life but is also known to be produced by nonbiologic processes.

Traditional organic biomarkers used in the fossil fuel industry2 Magnetite produced by some magnetotactic bacteria2 Some extreme examples of carbon isotopic fractionation Less intricate forms resembling known fossils, biofilm, mineralized microbes Presence and enhancement of nitrogen, phosphorous Ratios of certain elements such as phosphorous to uranium Iron isotopic fractionation Sulphur isotopic fractionation Many fossil-like morphologies Amino acids Polycyclic aromatic hydrocarbons (degradation product of life, product of burning, etc.) Micrometer-size spherical or ovoid objects Many low temperature minerals Specific mineral compositions and associations Non-equilibrium coexistence or zoning in minerals
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Stable biomarker which may be used in the search for extinct life (survives on the order of 2.7 billion years). 21. Februar 2009 May potentially be Category 1 instead of Category 2


Variations in Isotopic Abundance: Carbon
13C =

( (
13

C C

12

C

13

12

) C)

Sample ref.

- 1 в 1000

The Biomarker Guide, K.E. Peters, C.C. Walters, and J.M. Moldowan, Cambridge, 2005
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Sulphur Isotopes on Earth, Meteorites and Moon
Terrestrial Meteoritic Lunar

34 S 32 S 34 S = 34 32 SS 21. Februar 2009

( (

) )

Sample CDM

- 1 в 1000

Kaplan, I. R., Stable Isotopes as a Guide to Biogeochemical processes, Proc. R. Soc. Lond. B, 189, (1975) 183­211.

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Membrane-Inlet Mass Spectrometer (MIMS)
MIMS instrument was designed for a thermal drill for a NASA mission study. Designed to work to 180 bars, e.g. the ice sheet thickness.

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Conclusions
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We developed two miniaturised laser mass spectrometers for planetary research (BepiColombo/MSE)
-- Lander LMS: ь60 x 160 mm, 550 g, 3W / 8.5W -- Rover LMS: 70 x 50 x 50 mm3, 280 g, 3 W

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Upcoming application of an LMS instrument will be on the Phobos-Grunt mission Current development of ice surfaces similar to Europa Concepts developed for an instrument to be part of a melting probe payload
-- Europa -- Mars pole -- ...

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Space Applications
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Limited resources
-- -- -- -- Power Volume Mass Data rate

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Autonomous operation
-- Simple instrument operation

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Environmental
-- Vibration, shock -- Thermal -- Acoustic

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Mission duration Radiation environment
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Lander LMS Resources
Volume [mm3] Ion optics HV electronics Laser electronics Digital Interface Data acquisition DPU Harness Total ь60 x 160 -- -- 40 x 50 x 10 100 x 100 x 25 70 x 80 x 20 4x1m Mass [gr] 150 30 40 20 190 70 50 550 2900 / 8250 Power [mW] -- 50 / 50 500 / 2900 150 / 200 1700 / 3100 500 / 2000

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U spectrum

238

U H O
16 235 1 238

U

U16O

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Resources of Rover LMS Flight Design
Mechanical dimensions Mass Mounting location Sensor 70 x 30 x 40 mm3, including electronics and laser system Sensor 280 g overall Sensor entrance deployed to planetary ground by pointing compartment entrance onto object 1­300 amu m/І m = 180 Standby 200 mW, operation average 3 W, peak 5 W
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Mass range Mass resolution Power

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Concentration in % weight
Element Au Pt Pd In Ag C Fe H Zn Re
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LASMA analysis 84.68 7.12 4.30 1.22 1.10 2.5x10 0.49 0.31 0.13 0.65 Max
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Reference 84.5 6.9 5.0 1.75 1.0 2x10 0.7 N/I 0.15 0.1
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-3