X‐ray computed tomography imaging: A not‐so‐nondestructive technique

Giant micrometeorites (MMs; 400–2000 µm) are exceedingly rare and scientifically valuable. Three‐dimensional nondestructive characterization by X‐ray computed tomography (X‐CT) provides information on the petrography and thus petrogenesis of MMs and serves as a guide to maximize subsequent multi‐analytical studies on such precious planetary materials. Here, we discuss the results obtained by X‐CT on 22 giant MMs and the classification based on their 3‐D density contrast images. Scoriaceous and unmelted MMs have distinct porosity ranges (10–40 vol% versus 0–25 vol%, respectively). We observe a porosity variation inside scoriaceous MMs, which allows their atmospheric entry flight history to be resolved. For the first time, spinning entry is explicitly demonstrated for four partially melted MMs. Furthermore, we are able to resolve the thermal gradient in a single particle, based on porosity variation (seen as a progressive increase in pore abundance and size with higher peak temperatures). Moreover, we explore parent body alteration through the 3‐D analysis of pores distribution, showing that shock fabrics are either absent or weakly developed in our data set. Finally, owing to the detection of pseudomorphic chondrules, we estimate that the intensively aqueously altered C1 or CI‐like material could represent 18% of the MM flux at this size fraction (400–1000 µm).

Section: Discussionmentioning

confidence: 99%

X‐ray computed tomography: Morphological and porosity characterization of giant Antarctic micrometeorites

Dionnet

Suttle

Longobardo

et al. 2020

“…Being totally nondestructive, FTIR microtomography and its characterization of the organics could be the first step of analyses. Some studies suggested that X-CT can cause some damage to the organics (see e.g., Sears et al 2016;Hanna and Ketcham 2017); however, this strongly depends on the experimental conditions used (namely energy and photon density). In any case, in future studies, it will be important to perform FTIR microtomography before X-CT to be able to address this issue.…”

Section: Advantages and Limitations Of Ft-ir Microtomographymentioning

confidence: 99%

Combining IR and X‐ray microtomography data sets: Application to Itokawa particles and to Paris meteorite

Dionnet

Brunetto

Aléon-Toppani

et al. 2020

In the near future, a new generation of sample return missions (Hayabusa2, OSIRIS‐REx, MMX, etc.) will collect samples from small solar system bodies. To maximize the scientific outcome of laboratory studies and minimize the loss of precious extraterrestrial samples, an analytical sequence from less destructive to more destructive techniques needs to be established. In this work, we present a combined X‐ray and IR microtomography applied to five Itokawa particles and one fragment of the primitive carbonaceous chondrite Paris. We show that this analytical approach is able to provide a 3‐D physical and chemical characterization of individual extraterrestrial particles, using the measurement of their 3‐D structure and porosity, and the detection of mineral and organic phases, and their spatial co‐localization in 3‐D. We propose these techniques as an efficient first step in a multitechnique analytical sequence on microscopic samples collected by space missions.

“…For example, Sears et al. () and Sears et al. () found that the thermoluminescence (TL) intensity of the Bruderheim L chondrite is substantially altered by exposure to the ionizing radiation of μCT imaging experiments.…”

Section: Introductionmentioning

confidence: 99%

Effect of polychromatic X‐ray microtomography imaging on the amino acid content of the Murchison CM chondrite

Friedrich

Dworkin

Glavin

et al. 2018

Self Cite

X‐ray microcomputed tomography (μCT) is a useful means of characterizing cosmochemical samples such as meteorites or robotically returned samples. However, there are occasional concerns that the use of μCT may be detrimental to the organic components of a chondrite. Small organic compounds such as amino acids comprise up to ~10% of the total solvent extractable carbon in CM carbonaceous chondrites. We irradiated three samples of the Murchison CM carbonaceous chondrite under conditions akin to and harsher than those typically used during typical benchtop X‐ray μCT imaging experiments to determine if detectable changes in the amino acid abundance and distribution relative to a nonexposed Murchison control sample occurred. After subjecting three meteorite samples to ionizing radiation dosages between ~300 Gray (Gy) and 3 kGy with bremstrahlung X‐rays, we analyzed the amino acid content of each sample. Within sampling and analytical errors, we cannot discern differences in the amino acid abundances and amino acid enantiomeric ratios when comparing the control samples (nonexposed Murchison) and the irradiated samples. We conclude that a polychromatic X‐ray μCT experiment does not alter the abundances of amino acids to a degree greater than how well those abundances are measured with our techniques and therefore any damage to amino acids is minimal.