Development of surface materials analogues of the main-belt comet 133P/Elst-Pizarro

Introduction:

The main-belt comets (MBCs) are objects that exhibit cometary activity but occupy stable orbits in the main asteroid belt. MBCs are considered as a hidden reservoir of water ice in the Solar System, and have the potential in terms of scientific research and space resource utilization in the future (Hsieh, 2020). The main-belt comet 133P/Elst-Pizarro (133P) is the first discovered  and best characterized member of the MBCs. Dynamically, 133P fits well in Themis asteroid family (Hsieh et al., 2004). The spectra of 133P resembles best of B-type asteroid and is very similar to those of Themis family members (Hsieh et al., 2008; Licandro et al., 2011). Meteorites that can be compared to the Themis family are CI, CM, CR, CI-unusual, and CM-unusual (Clark et al., 2010).

This abstract described a series of methods to manufacture ice-bearing regolith simulant samples for 133P in the laboratory. The characteristics of the analogue are also obtained. The methods in this work can also be applied to the preparation and application of surface regolith simulants of other icy celestial bodies in the Solar System, which can provide scientific basis and ground truth for remote sensing detection, landing sampling and in-situ resource utilization in future probes.

 

Method:

The study involved creating a surface material analogue based on the observed and modeled composition of 133P. The surface regolith of the cometary is mainly composed of water ice, refractory organic matter, and minerals. A basic recipe for the prototype analogue is based on the observation and compositional modeling spectrum of 133P (Rousselot et al., 2011) and the modal mineralogy of the related meteorites. The analogue was developed using a mix of water ice, silicates (serpentine, olivine, pyroxene), amorphous carbon, and organics. Two methods were employed for preparing the ice-dust mixtures:

Mixing pre-prepared micron-sized ice particles with comet surface soil mimic powder in a cryogenic freezer.

Adding the cometary dust simulant to a dewar with generated ice particles, then separating the mixture after liquid nitrogen volatilization.

Fig. 1 Cometary surface regolith ice-dust analogue according to method 1

Fig. 2 Cometary surface regolith ice-dust analogue according to method 2

Characterization of the analogue included optical microscopy for morphology and particle size, laser diffraction for particle size distribution, X-ray fluorescence (XRF) spectrometry for bulk chemistry, and spectrophotometric analysis for optical properties.

Results:

The developed analogue successfully mimics the surface regolith of 133P. Optical microscopy revealed that the water ice particles were spherical, ranging from 2-12 μm. Laser diffraction indicated a broad particle size distribution, with the majority of particles falling within the expected size range for cometary dust. XRF spectrometry confirmed that the major elemental composition of the analogue closely matches that of carbonaceous chondrites, specifically CO3 chondrites, which are considered analogues for cometary material. Spectrophotometric analysis showed that the analogue's spectrum aligned well with observed data for 133P, validating the compositional accuracy of the analogue.

Fig.3 Spectrum of the cometary material analogue (red line); visible spectrum of 133P reported by Licandro et al. (2011, yellow spots); near-infrared spectrum of 133P reported by Rousselot et al. (2011, blue spots).

Conclusion:

 Our cometary analogue provides a robust foundation for simulating cometary processes such as sublimation, deposition, and irradiation, crucial for understanding the early Solar System. Additionally, it supports the development of technologies for future space missions, including sample return missions and in-situ resource utilization.

References:

Hsieh, Henry. "Active Asteroids: Recent Results and Future Prospects." 44th COSPAR Scientific Assembly. Held 16-24 July 44 (2022): 200.

Licandro, J., et al. "Testing the comet nature of main belt comets. The spectra of 133P/Elst-Pizarro and 176P/LINEAR." Astronomy & Astrophysics 532 (2011): A65.

Clark, Beth Ellen, et al. "Spectroscopy of B‐type asteroids: Subgroups and meteorite analogs." Journal of Geophysical Research: Planets 115.E6 (2010).

Rousselot, Philippe, Christophe Dumas, and Frédéric Merlin. "Near-infrared spectroscopy of 133P/Elst-Pizarro." Icarus 211.1 (2011): 553-558.