MicrOmega: a generic hyperspectral microscopic imager to characterize extraterrestrial samples, in space and in the lab

Introduction: Analyses of extraterrestrial samples enables to better assess the processes responsible for the wide diversity of solar system properties. Specifically, NIR hyperspectral imagery complement the NIR remote sensing of asteroids and planetary surfaces, in enabling tracking diagnostic major and minor constituents of sampled material, that are witnesses of the formation and evolution of their parent bodies, with their potential role when imbedded within Solar System objects. MicrOmega has been developed to detect and map such key constituents in mm-sized samples, directly in situ as a space instrument, and in the laboratory whenever returned samples are available.

 

The Instrument: MicrOmega is a near-IR hyperspectral microscope developed at the Institut d’Astrophysique Spatiale in Orsay, France [1]. The instrument delivers (x,y λ) spectral cubes from 0.99 to 3.65 µm, over a 5×5 mm² field of view, with a ~20 µm pixel size. Its spectral range, spectral sampling and focal depth have been chosen to enable, in a compact, light and robust instrument, the identification of most potential constituents: silicates, oxides, salts, hydrated minerals, ices and frosts, as well as organic compounds, discriminating between specific members in each family (e.g. low and high Ca pyroxenes, forsterite and fayalite, Mg and Al rich phyllosilicates, aliphatic and aromatic compounds, different types of carbonates and sulfates, etc. [2]). One prime goal is to observe the interrelation between the various phases and minerals, including those only present in small abundances (e.g. a few grains within the rock) or restricted to fractures or pores. Moreover, data processing enables not only to identify and locate grains of specific composition, but also to quantify their abundance.

 

MicrOmega on Mars: MicrOmega has been developed to be the first instrument to analyse the drilled samples inside the Rosalind Franklin rover of the ExoMars mission, to be launched in 2028 [1]. The rover will drill samples down to 2 m depth at the surface of Mars, and distribute them to the Analytical Laboratory Drawer (ALD) in the body of the rover for detailed mineralogic and molecular analysis. MicrOmega aims to characterize the composition of these samples at the grain size scale, in a non-destructive way.

Together with the flight model integrated in Rosalind Franklin, a flight spare of MicrOmega is installed in a dedicated set-up at Institut d’Astrophysique Spatiale [3]. The instrument is set in a glove box under controlled atmosphere and temperature to allow the safe use of the instrument under different conditions. A large number of synthetic and natural Earth analogues for Mars have been analysed within this set-up and has shown the capability of MicrOmega to map a large diversity of minerals [2], and to detect organic molecules even in small amount, in different mineral settings.

 

MicrOmega and extraterrestrial samples: MicrOmega is now  also used to analyse extraterrestrial samples in the lab.

The set-up with the flight spare of MicrOmega/ExoMars allows the analysis of precious extraterrestrial samples continuously out of contact with the Earth atmosphere. Meteorites, and samples from Ryugu (JAXA/Hayabusa2 mission), Bennu (NASA/OSIRIS-ReX mission), and the Moon (CNSA/Chang’E-5 mission [4]) have been and will be analysed in this facility.

Another model of MicrOmega has been integrated in the curation facility for the Ryugu and Bennu returned samples at ISAS/JAXA extraterrestrial samples curation center (EsCuC). This MicrOmega model observes all samples from both carbonaceous asteroids curated in Japan, maintained in clean chambers under N₂, before their distribution to the scientific community [5, 6]. With these very dark samples, MicrOmega is sensitive to phyllosilicate signatures and how they are affected by space weathering (e.g. [7]), carbonates, phosphates, and CH- and NH-rich compounds as small as a few 10s µm.

In particular, MicrOmega has been able to help us better understand the water/rock interactions in the Ryugu and Bennu’s parent bodies in the early Solar System. For example, the instrument has mapped and distinguished different types of carbonates in samples from both asteroids, and has quantified their presence over a large portion of the returned material [8, 9].

MicrOmega has also been used to study the presence of key elements for the appearance of life, that have been delivered to the early Earth by carbonaceous asteroids: the instrument identified in Ryugu a class of hydrated minerals rich in P, Mg and ammonium that are more easily soluble than previously identified Ca-phosphates [10] ; it has also shown a number of grains enriched in NH associated to ammonium-bearing phyllosilicates both in Ryugu and Bennu [11]. 

 

[1] Bibring et al. (2017) Astrobiology, 17, 621-626. [2] Loizeau et al. (2022) Astrobiology, 22, 263-292. [3] Loizeau et al. (2020) PSS, 193, 105087. [4] Jiang et al. (2026) this conference [5] Pilorget et al. (2022) Nature Astronomy, 6, 221-225. [6] Pilorget et al. (2025) Nature Comm., 16, 9532 [7] Nardelli et al. (2026) this conference. [8] Loizeau et al. (2023) Nature Astronomy, 7, 391-397. [9] Mahlke et al. (2026) accepted in the Planetary Science Journal. [10] Pilorget et al. (2024) Nature Astronomy, 8, 1529-1535. [11] Jiang et al. (2026) Nature Comm., in press.