Non destructive methodology to study GRO 95517 antarctic meteorite

INTRODUCTION
Returning sample missions have gained
increasing attention in the last decades since
the only way to know the planetary surface's
composition and reconstruct the history
of geological processes is to analyse
samples using Earth-ground laboratorybased
techniques.
The employment of a non-or minimally destructive
protocol of analyses to carry out a
comprehensive characterisation is crucial
to preserving very precious extraterrestrial
samples.
On the other hand, non-destructive analyses
on samples of meteorites and micrometeorites
were yet successfully applied on Al-
Haggounia 001[1] and the micrometeorite
found on Mt. Gariglione, southern Italy[2].
With this aim, we are studying a fragment
of an antarctic meteorite named GRO
95517, a EH3 chondrite, found in 1995 in
Grosvenor Mountains (Antarctica – NZ).
The purpose of this investigation is the
study of mineralogical composition with
particular attention to the rare phases, mineral
distribution and association, texture and
microstructures in order to provide further
information on the origin and evolution of
this meteorite.
METHODS
The fragment was studied by Scanning
Electron Microscope (SEM) and microcomputed
tomography (μ-CT).
The correlation between SEM-EDS data,
chemical mapping and 3D reconstruction by
μ-CT allows to obtain us a volumetric reconstruction
of the fragment in nondestructive
way.
RESULTS
Optical analyses
GRO 95517 consists of chondrules
formed by pyroxene (enstatite) immersed in
a matrix composed by mesostases of plagioclase
in which nickel-iron alloys, sulfides
(daubréelite, oldhamite and troilite) and
phosphides (schreibersite) are disseminated.
The presence of oxidised phases such as
jarosite and oxides testify an heavily weathering.
The sample also exhibits several fractures.
Optical observations on thin section
show two families of enstatite chondrules
(EC): radial-pyroxene chondrules consisting
of fan-like arrays of enstatite and porphyritic
chondrules containing mainly enstatite.
Other mineralogical phases forming both
chondrules and mesostasis are mainly sulfides
and plagioclases.
In one enstatite chondrule we can appreciate
a “faulting” structure.
Sometimes, plagioclase and quartz aggregates
are observed.
SEM analysis
The S.E.M. analysis confirmed the presence
of pyroxene (enstatite), which is the
main constituent of chondrules. Furthermore, a significant distribution
of sulfides was detected, relatively
homogeneously dispersed throughout the
thin section. Through SEM analysis, these
sulfides are oldhamite, daubréelite, and
troilite.
Significant is also the presence of ironnickel
alloys (kamacite), which stand out
due to their bright white appearance in BSE
images.
Secondary mineralogical phases related
to terrestrial weathering alteration are limonite
(yellowish-brown in color) and jarosite.
Microcomputed Tomography (μ-CT)
This non-invasive technique was crucial
to obtain bulk information about the outer
and inner parts of the sample, thanks to the
ability to provide 3D reconstruction of meteoritic
fragments. GRO95517 is characterized
by a high presence of pores that, in
most cases, are filled by secondary phases. In the cross section minerals
with different attenuation coefficients
and chondrules can be observed.
CONCLUSION
The Antarctic meteorite GRO 95517 is
characterized by primary phases such as
enstatite, kamacite and troilite surrounded
by a glassy mesostasis. Few secondary
phases were recognized, that indicate a high
degree of weathering (limonite and jarosite).
The integration of SEM-EDS data,
chemical maps and 3D μ-CT reconstruction
allows to obtain a volumetric reconstruction
of the fragment, providing valuable information
on its internal structure without
compromising its integrity.

REFERENCES:
[1] Manzari, P., Mele, D., Tempesta, G. &
Agrosì, G. (2023) – New insights on the
porosity and grain features of Al Haggounia
001, an impact-melt meteorite, 1-10.
[2] Agrosì, G., Manzari, P., Mele, D., Tempesta,
G., Rizzo, F., Catelani, T., Cheng, G.,
Yao, N., Villenueve, J. & Bindi, L. (2025) –
Unique (Al, Cu)-alloys discovered in a micrometeorite
from Southern Italy. Communications
earth & environment, 1-10.