54th Lunar and Planetary Science Conference 2023 (LPI Contrib. No. 2806)

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EXPERIMENTAL ANALOG FOR HIGH-SPEED PARTICLE CAPTURE FROM IO VOLCANIC PLUME.
Z. Vaci1,2, J. J. Gillis-Davis1,3, R. C. Ogliore1,3, and P. Koefoed1,2. 1McDonnell Center for Space Sciences, Washington
University in St. Louis, 2Department of Earth and Planetary Sciences, Washington University in St. Louis,
3
Department of Physics, Washington University in St. Louis. vaci@wustl.edu.
Introduction: The inner-most Jovian moon Io issubjected to intense tidal heating via the Laplaceresonance between it, Europa, and Ganymede. As aresult, Io is the most volcanically active body in thesolar system, with hundreds of active volcanoes
observed erupting on its surface by the two Voyager
spacecraft, the Hubble Space Telescope, Galileo, New
Horizons, and most recently, Juno [1]. Remote sensing
observations suggest that the erupting lava is basaltic toultramafic, with eruption temperatures as high as ~1600°C [2]. However, the composition of the lava can only
be roughly modelled with data gathered from remotesensing observations.
Several volcanic ash plumes have been observed
erupting simultaneously from the surface of Io, with thelarger Pele-class plumes reaching ~350 km in height [3].
To constrain the composition of material erupting fromIo, a spacecraft will need to fly through a volcanic
plume, collect a sample, and return the material to Earthfor analysis [4]. Sample return will allow us to measureboth micrometer-scale and bulk chemical and isotopic
compositions of volcanic particles and associatedvolcanic gases erupted from Io. Sample collection will
likely proceed at high speed (~6 km/s), such that plume
sampling of solid particles will be analogous to theStardust comet sampling mission. While in situ analysesof particles captured at hypervelocity has been
conducted successfully for >15 years with the Stardust
samples from Comet Wild 2 [5], bulk geochemical
analysis will require the development of new methods
that maximize the science return of collected material.
To that end, we conducted a study using laser irradiationof analog materials into Si wafers.
Methods: For the purpose of simulating
hypervelocity impacts, a Continuum Surelite I-20
Nd:YAG laser was used to deposit energy onto a 5 × 5mm silicon wafer coated with fine (<10 µm) San Carlosolivine dust. The olivine dust was sandwiched between
the silicon chip and a glass cover slide. This method
kept the dust from being dispersed by the shock of thelaser.
The laser wavelength was 1064 nm. Its pulse
duration was 6–8 ns, which is comparable to a
micrometeorite bombardment timescale. We operated
the laser in single shot mode. The diameter of thefocused beam was about 1 mm on the Si wafer. The
position of each laser hit was controlled by an X- Yactuated mirror. The wafer was shot approximately 5060 individual times. Each shot was with 30 mJ of energy

or 121 W/mm2 of power. All experiments wereperformed under vacuum (1x10-6 torr).

Figure 1. BSE (top) and X-ray (middle and bottom)
images of a lased area in an Si wafer.

54th Lunar and Planetary Science Conference 2023 (LPI Contrib. No. 2806)

The lased wafers were cleaned of loose dust withcompressed N2 gas and imaged using a Tescan Mira3
FEG-SEM operating in backscattered electron (BSE)
mode. X-ray maps were collected using an EDAX EDX
system and processed with EDAX Teams software.
Samples were weighed and digested in a 2:1 mixture ofconcentrated HF and HNO3 and fluxed in 6N HCl andconcentrated HNO3 to remove any fluorides. They werethen dissolved in 2% HNO3 and diluted for major andtrace element measurement using a Thermo iCAP Q
quadrupole mass spectrometer.
S.C.
Exp. Shots
Si Wafer
Olivine
Blank
Na2O
0.023
0.002
0.0004
MgO
47.07
0.02
0.0002
Al2O3
0.093
0.005
0.0002
P2O50.014
0.001
0.0005K2O
0.006
0.001
0.0001
CaO
0.150
0.003
0.002
TiO2
0.004
0.00020.00006
Cr2O3
0.031
0.000020.00002
MnO
0.121
0.00005
0.00002
FeO
8.71
0.003
0.0002SiO243.778n/an/aMg#90.60
90.66
63.05
Table 1. Major and minor element analyses of theolivine, experimental shots, and the blank Si wafer, inwt.%. SiO2 was determined by subtraction. Mg# = mol.
Mg/(Mg+Fe); n/a = not applicable.
Results: BSE and X-ray images of the laser-etchedcraters show that the Si wafer was partially melted andablated, while olivine grains were partially melted andincorporated into the crater material (Fig. 1). X-ray
maps show resolvable quantities of Mg and Fe
incorporated into the craters. Results of major and minor
element analysis (Table 1) indicate that the compositionof the olivine was not significantly altered by the lasingprocess. While the minor elements are present inconcentrations too low to be measured accurately andhave likely been affected by contributions from the Si
wafer and fractionation due to ablation, Mg, Fe, and Mn
were stoichiometrically conserved. The Mg# of theexperimental result is identical within error to the Mg#of the olivine.
The trace elements present in the olivine are alsopresent in the experimental shot analyses, althoughmany are likely subject to similar effects as the minorelements. Many trace elements were either below thedetection limit of the iCAP Q mass spectrometer or too
low to quantify accurately. Importantly, several rareearth elements (REE) were quantifiable (Fig. 2). The

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light REE La, Ce, Pr, and Nd show a pattern in theexperimental results similar to that of the olivine, inhigher concentrations than in the Si wafer. The rest areeither below detection limit or overlap with thebackground measurements obtained by analyzing theblank Si wafer. Eu is in a much higher concentration
than the other REE, potentially due to a redox effect.
The calculated total mass of olivine implanted into
the 0.000025 m2 Si wafer is 0.010 mg, or 407 mg/m2.
This is within the expected Io sampling range of 10-100
mg per 0.1 m2 of collector area.

Figure 2. Chondrite normalized REE diagram showing
experimental results, S.C. olivine, and Si wafer blank.
Discussion: While remote sensing of Io allows forthe determination of geophysical constraints such as
tidal Love numbers and libration amplitude, parameterssuch as silicate melt percentage and extent of
fractionation can only be measured geochemically in a
returned sample. Our results suggest that high speed
capture of small particles can produce quantifiable
results via bulk analysis. While this pilot study showsthat the laser and acid dissolution ICP-MS methods arefeasible, many variables remain to be constrained.
Future work using higher purity Si will vary thecomposition of material lased to include various igneousminerals such as pyroxenes, feldspars, oxides, andvolcanic glasses. Quantities of material and laser shot
intensity will be varied to produce fractionation curves
for minor and trace elements. Additional experiments
using different substrates, such as BaF2 for oxygenisotopic analysis, will also be conducted. Results will beverified by performing light gas gun shots at
hypervelocity into solid and porous substrates.
References: [1] Mura A. et al. (2020) Icarus, 341,113607. [2] Keszthelyi L. et al. (2007) Icarus, 192, 491502. [3] Spencer J. R. et al. (2007) Science, 318 (5848),240-243. [4] Ogliore R. C. et al. (2023) LPS LIV (thisconference). [5] Postberg F. et al. (2014) MaPS, 49:9,1666-1679.