# Surface properties of the Kalliope-Linus system from ALMA and VLA data

**Authors:** Katherine de Kleer, Saverio Cambioni, Bryan Butler, Michael Shepard  
**arXiv:** [2409.12364](https://arxiv.org/abs/2409.12364)  
**Date:** 2024-09-18  
**Summary page:** https://www.summarizepaper.com/en/paper/2409.12364v1/

## Key points

- Authors Katherine de Kleer, Saverio Cambioni, Bryan Butler, and Michael Shepard conducted a study on the surface properties of the Kalliope-Linus system.
- Observations from ALMA and VLA were used to analyze thermal emission at radio wavelengths to understand metal abundance and distribution in asteroid surfaces.
- Focus was on M-type asteroid (22) Kalliope and its moon Linus, capturing data at 1.3, 9, and 20 mm wavelengths over Kalliope's rotation period.
- Results showed Kalliope's thermal inertia of 116$^{+326}_{-91}$ J m$^{-2}$ s$^{-0.5}$ K$^{-1}$ and emissivity values at different wavelengths.
- Linus displayed lower emissivity values compared to Kalliope, indicating a less metal-rich surface composition.
- Spatial variations in Kalliope's emissivity suggested enhanced metal content in the northern hemisphere region.
- Findings support a scenario where Linus may have formed from reaggregated ejecta following an impact onto a differentiated Kalliope.
- Iron likely exists on Kalliope's surface in metallic grains constituting approximately 25% of the composition.

## Summary

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Authors Katherine de Kleer, Saverio Cambioni, Bryan Butler, and Michael Shepard present a comprehensive study on the surface properties of the Kalliope-Linus system. Using observations from the Atacama Large Millimeter/submillimeter Array (ALMA) and the Karl G. Jansky Very Large Array (VLA), they analyze thermal emission at radio wavelengths to understand the abundance and distribution of metal in asteroid surfaces. Their findings shed light on planetesimal differentiation processes. The team focused their observations on the M-type asteroid (22) Kalliope and its moon Linus, capturing data at 1.3, 9, and 20 mm wavelengths over most of Kalliope's rotation period. The high-resolution 1.3 mm data provided insights into Kalliope's surface features with approximately 30 km resolution, while both the 1.3 mm and 9 mm data allowed for the differentiation of Linus from Kalliope. Their analysis revealed a thermal inertia for Kalliope of 116$^{+326}_{-91}$ J m$^{-2}$ s$^{-0.5}$ K$^{-1}$ along with emissivity values of 0.65$\pm$0.02 at 1.3 mm, 0.56$\pm$0.03 at 9 mm, and 0.77$\pm$0.02 at 20 mm. Interestingly, Kalliope exhibited suppressed millimeter wavelength emission compared to centimeter wavelengths and showed depolarization effects. In contrast, Linus displayed lower emissivity values of 0.73$\pm$0.04 at 1.3 mm and 0.85$\pm$0.17 at 9 mm, indicating a less metal-rich surface composition compared to Kalliope. Spatial variations in Kalliope's emissivity highlighted a region in its northern hemisphere with a high dielectric constant, suggesting an enhanced metal content in that area. These findings support a scenario where Linus may have formed from reaggregated ejecta following an impact onto a differentiated Kalliope, resulting in varying metal distributions between the two bodies' surfaces. The team also noted that iron on Kalliope's surface likely exists in metallic grains constituting approximately 25% of the composition. Overall, this comprehensive study provides valuable insights into the surface properties of the Kalliope-Linus system and contributes to our understanding of asteroid composition and formation processes within our solar system.