Right after seeing that the Planetary Research journal began publishing its first papers, I checked the articles and letters, and especially the letter by Christian Renggli and others titled “The SiO2 abundance on the surfaces of the Moon and Mercury” piqued my interest immediately. Only some of the intriguing parts of the letter for me: the focus on planetary/moon surface composition estimation by remote measurements, new calibration of the Christiansen Feature – silicon dioxide model for concentration estimations, producing laboratory data to more accurately use this, checking the estimations with Lunar Reconnaissance Orbiter – LRO Diviner data, and also the newly calibrated polynomial model’s potential to be utilized for Mercury composition estimation.
Introduction
First, let me briefly explain some terms above to put this in perspective. Silicon dioxide, or SiO2, is a fundamental mineral component in rocky bodies; it occurs not only on Earth, but also on the Moon, Mercury, and other rocky bodies. The type of the silicon dioxide-bearing minerals/rocks changes the material’s characteristics, including how it interacts with light. To understand the intrinsic properties, we also conduct spectroscopic measurements. The Christiansen Feature in the infrared spectrum is among this step. Briefly, Christian Christiansen showed that different minerals can filter out different parts of the spectrum to produce any colour from white light. Similarly, a specific channel for silicate-bearing minerals exists owing to the same phenomenon, which is what is meant by the Christiansen Feature in the context of lunar and other rocky bodies’ surface composition studies. Greenhagen’s (2009) PhD thesis is very illuminating on this effect. As the CF is sensitive to changing mineral compositions, silicon dioxide concentration, and environmental conditions surrounding the area of interest, precisely measuring its central wavelength location gives us key information about the surface.
Renggli et al. (2026)’s study with a new Christiansen Feature – Silicon Dioxide Model
This is where Renggli et al. (2026)’s study enters the stage, especially to extract more accurate information for regions with relatively higher silicon dioxide concentration. For this purpose, they synthesized beads in seven different silicon dioxide concentrations, ranging from 0.5 to 97 % (by weight). Then, they were able to provide a new Christiansen Feature – silicon dioxide model calibration line, which is also effective for very high silicon dioxide concentrations. This new model was more effective than its counterparts from the literature, especially for highly silicic central mare region minerals. After that, they compared the results of their newly calibrated model to the ground truth from the sampled sites of Apollo 11, 12, 14, 15, 16, 17, Luna 16, 20, 24, and Chang’e 5, 6 missions. Furthermore, this model improved the utility of Diviner-sourced CF data/maps, which Diviner has been collecting since 2009.
Last but not least, the authors made their data, published infrared spectra, and chemical compositions available.
Have a read!
References
Greenhagen, B. T. (2009). Thermal emission remote sensing of the moon: Design and development of Diviner lunar radiometer compositional capabilities [PhD Thesis]. University of California, Los Angeles.
Renggli, C., Andreas, M., Weber, I., Reitze, M. P., Di Rocco, T., Berndt, J., Pack, A., & Hiesinger, H. (2026). The SiO2 abundance on the surfaces of the Moon and Mercury. Planetary Research, 1(1). https://doi.org/10.53480/bf74-m226
