NASA's interstellar collector from the Stardust mission captured several particles that are now thought to be of interstellar origin. We analyzed two of these via nanodiffraction at the European Synchrotron Radiation Facility (ESRF) and found them to contain crystalline components. The unit cell of the crystalline material is determined from the diffraction patterns and the most likely mineral components are identified as olivine and spinel

Achilles, Cheri

Allen, Carlton

Ansari, Asna

Bajt, Sasa

Bassim, Nabil

Bastien, Ron S.

Bechtel, H. A.

Borg, Janet

Brenker, Frank E.

Bridges, John

Brownlee, Donald E.

Burghammer, Manfred

Cloetens, Peter

Gainsforth, Zack

Lemelle, Laurence

San Tresseras, Juan-Angel

Sandford, S. A.

Schmitz, Sylvia

Schoonjans, Tom

Silversmit, Geert

Simionovici, Alexandra

Sole, Vicente A.

Vekemans, Bart

Vincze, Laszlo

Zolensky, Michael E.

NASA Technical Reports Server

IDENTIFICATION OF CRYSTALLINE MATERIAL IN TWO INTERSTELLAR DUST CANDIDATES 
FROM THE STARDUST MISSION. Zack Gainsforth, Alexandre Simionovici, Frank E. Brenker, Sylvia Schmitz, 
Manfred Burghammer, Peter Cloetens, Laurence Lemelle, Juan-Angel Sans Tresseras, Tom Schoonjans, Geert Sil-
versmit, Vicente A. Solé, Bart Vekemans, Laszlo Vincze, Cheri Achilles, Carlton Allen, Asna Ansari, Sasa Bajt, 
Nabil Bassim,  Ron S. Bastien, H. A. Bechtel, Janet Borg, John Bridges, Donald E. Brownlee, Mark Burchell, Anna 
L. Butterworth, Hitesh Changela, Andrew M. Davis, Christine Floss, George Flynn, Patrick Fougeray, David Frank, 
Eberhard Grün, Philipp R. Heck, Jon K. Hillier, Peter Hoppe, Bruce Hudson, Gary Huss, Joachim Huth, Brit Hvide, 
Anton Kearsley, Ashley J. King, Barry Lai, Jan Leitner, Ariel Leonard, Hugues Leroux, Robert Lettieri, William 
Marchant, Larry R. Nittler, Ryan Ogliore, Frank Postberg, Mark C. Price, S. A. Sandford, Kate Schreiber, Ralf 
Srama, Thomas Stephan, Veerle Sterken, Julien Stodolna, Rhonda M. Stroud, Steven Sutton, Mario Trieloff, Peter 
Tsou, Akira Tsuchiyama, Tolek Tyliszczak, Andrew J. Westphal, Naomi Wordsworth, Daniel Zevin, Michael E. 
Zolensky, >30,000 Stardust@home dusters , See http://www.ssl.berkeley.edu/∼westphal/ISPE for affiliations. 
 
Introduction:  NASA’s interstellar collector from 
the Stardust mission captured several particles that are 
now thought to be of interstellar origin.  We analyzed 
two of these via nanodiffraction at the European Syn-
chrotron Radiation Facility (ESRF) and found them to 
contain crystalline components.  The unit cell of the 
crystalline material is determined from the diffraction 
patterns and the most likely mineral components are 
identified as olivine and spinel. 
Experimental:  Tracks I1047,1,34 (Hylabrook) 
and I1043,1,30 (Orion/Sirius) were extracted as aero-
gel keystones [1] and studied using ESRF beamlines 
ID13 and ID22 using XRF and nanodiffraction. Hy-
labrook was rotated through 80º in 0.5º increments to 
produce a pseudo-powder pattern using 13895 eV pho-
tons on ID13. A 2D diffraction image was captured at 
each angle.  Orion/Sirius was rastered through a 13895 
eV beam on ID13 and a 17000 eV beam on ID22 with 
beam waists of about 200 nm to produce 2D spatial 
maps of the diffractive domains.  ID22 used a gray 
beam about 300 eV wide.  Exposure from the ID22 
beam apparently amorphized a subset of the crystalline 
phases seen previously in ID13, allowing us to unam-
biguously assign several peaks to a specific phase. 
Hylabrook:  d-spacings for the reflections ob-
served in Hylabrook are shown in Table 1.  The set of 
d-spacings observed allows unambiguous identifica-
tion of the unit cell geometry assuming we select the 
highest symmetry and lowest cell size possible.  We 
assumed one crystalline phase is responsible for the 
pattern, and excluded the cubic, hexagonal, trigonal, 
and tetragonal crystal systems with McMaille [2].  An 
orthorhombic cell is the next highest symmetry cell 
and is compatible with the diffraction pattern, which 
was then indexed on the assumption of orthorhombic 
symmetry.  The unit cell was computed with error bars 
using a Monte Carlo simulation written in MATLAB, 
and found to be a=4.85 ± 0.08 Å, b = 10.34 ± 0.16 Å, c 
= 6.08 ± 0.13 Å, α = β = γ = 90º where errors are 2σ.  
The only naturally occurring compatible mineral found 
in the PDF-4+ mineral database is the olivine family.  
We place no constraints on the chemical composition.  
Comparison of the observed peaks seen in Hylabrook’s 
diffraction pattern with a modeled fit for olivine shows 
that all modeled peaks are present in the measured data 
except for three very low intensity reflections.  All 
measured peaks are explained by modeled peaks as 
would be expected for a correct mineral identification.  
It should be noted that the unit cell dimensions are an 
experimentally measured quantity independent of the 
choice of olivine as the most likely crystalline phase. 
The diffraction pattern shows that multiple do-
mains are present through polygonalization of the dif-
fraction pattern.  Peak broadening is also present and 
was analyzed using the double-Voigt approach [3].  
The diffracting domain sizes are found to be larger 
than 15 nm (2σ) with an expectation value of several 
tens of nm.  We set an upper limit on the strain fields 
present at ≤ 0.3% (2σ) with an expectation value of 
0.2%.  According to Abramson et al. [4], this corre-
sponds to stresses ≤ 2 GPa in forsterite, which is con-
sistent with aerogel capture, but could also be native to 
the original grain.  This pressure regime may be incon-
sistent with an origin as secondary ejecta from an im-
pact on the spacecraft, but needs further investigation.  
Orion/Sirius: The set of d-spacings seen in 
Orion/Sirius is also consistent with olivine plus at least 
one other phase.  The most likely secondary phase is 
spinel where four peaks are identified from the scans 
on ID13 and ID22 and four are expected from the 
model.  The ID22 scan observed primarily the four 
spinel peaks.  This is consistent with the radiation 
hardness of spinel, so that it was the primary crystal-
line phase to survive the scan [5].  Two additional 
peaks exist in the ID13 data which cannot be ascribed 
to olivine or spinel, yet are also absent from the ID 22 
data indicating they belong to a third unidentified 
phase. A rigorous determination of the unit cells with-
out mineralic assumptions and a size-strain analysis of 
the phases is in progress. 
https://ntrs.nasa.gov/search.jsp?R=20120002791 2019-08-30T19:10:34+00:00Z
Orion/Sirius was mapped spatially in 2D by raster-
ing the sample with a 200 nm X-ray beam.  By analyz-
ing the presence or absence of specific diffraction re-
flections in the 2D dataset, we obtain a spatial image of 
the locations of these crystalline phases.  This is called 
an X-ray topograph, akin to a TEM darkfield image.  
Figure 1 shows topographs produced from both beam-
lines alongside a scanning transmission X-ray micros-
copy (STXM) image.  The leftmost topograph is from 
ID13 and shows a white pixel where any diffracting 
material exists.  This does not contain information 
about orientation or grain size since it contains a 
brightness contribution from all reflections measured 
in the diffraction pattern.  Outlined in red is a topog-
raph produced from one specific reflection, which in-
dicates that the entire region is diffracting as a single 
diffractive domain corresponding to olivine.  In this 
way, we see that the grain was approximately a micron 
long by a few hundred nm thick.  The middle frame 
shows the sum topograph from IDs22 which is the 
location of the spinel material.  None of these crystal-
lites are larger than a single pixel, and therefore ≤ 200 
nm across. 
Mass fraction: While we unambiguously show the 
presence of crystalline material in these particles, we 
do not place a strong constraint on the fraction of ma-
terial that could be crystalline.  Because the amorphous 
component of these grains is invisible to diffraction, 
additional work is in progress to place a useful number 
on the crystalline fraction by combining our datasets 
with STXM XANES, and through complete analysis of 
the topographs. 
Implications: Several lines of evidence point inde-
pendently to an interstellar origin for these particles 
[6].  The presence of diffracting crystalline material is 
not inconsistent with astronomical observations [7] 
indicating a large fraction of amorphous material in the 
ISM:  the fraction of crystalline material in these parti-
cles is not yet quantified, and may be in fact be small.  
Also, these particles, which are >1000 larger in mass 
than most interstellar dust particles, may not be miner-
alogically representative of the IS dust.   And finally, 
infrared spectroscopic techniques may not accurately 
determine crystallinity for nanograins. Nevertheless, 
the presence of some crystalline material indicates that 
at least some small fraction of the sample is of circum-
stellar origin and can survive transport through the 
ISM or is generated in the ISM through radiation in-
duced crystallization or other mechanisms. 
References: [1] Westphal A. J. et al. (2004) MAPS 
39, 1375. [2] Le Bail A., (2004) Powder Diffr. 19, 249. 
[3] Balzar D. and Ledbetter H. (1993) J. Appl. Cryst. 
26, 97. [4] Abramson E. et al (1997) J. Geophys. Res. 
102, 12253. [5] Hobbs L. et al. (1994) J. Nucl. Mater. 
216, 291. [6] Westphal, A. J. et al (2012) 43rd LPSC 
submitted. [7] Kemper, F. et al. (2004) ApJ, 609, 826. 
 
Hylabrook d-
spacings (Å) 
(hkl) indexed to 
olivine 
5.18 020 
4.39 110 
3.94 021 
3.80 101 
3.55 111 and 120 
3.06 121 and 002 
2.81 130 
2.55 131 
2.50 112 
2.38 200 
2.36 041 and 210 
2.30 122 and 140 
2.20 211 and 220 
2.06 132 and 221 
Table 1: Measured d-spacings for 
Hylabrook alongside the most 
likely reflections assuming olivine.  
Three peaks were not observed 
corresponding to the 022, 040 and 
141 reflections.  
  
 
Figure 1: Left image shows the sum of all topographs 
from ID 13, showing the location of all diffracting ma-
terial in the particle.  Overlay in red is a single topog-
raph from a reflection at 2.28 Å (olivine) showing one 
grain about 1 µm x 200-600 nm wide. Middle image 
shows the sum of topographs from ID 22 where most 
reflections map to spinel. Right image shows a STXM 
optical density map at 1568 eV for reference. 
 


Identification of Crystalline Material in Two Interstellar Dust Candidates from the Stardust Mission

Identification of Crystalline Material in Two Interstellar Dust Candidates from the Stardust Mission

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