Unveiling the origin and evolution of airless solar system bodies using reflectance spectroscopy

Jan. 8, 2026 | Aerospace Project Research Associate, ISAS people

Emma CAMINITI / Dept. of Solar System Sciences, ISAS

This article introduces the research of Aerospace Project Research Associate at the Institute of Space and Astronautical Science (ISAS). The Aerospace Project Research Associate program is a development opportunity for early-career scientists who aim to hone their research skills through participation in JAXA projects. This program places a strong emphasis on ISAS's unique approach to developing research capabilities.

Research Summary

Study of airless bodies in the solar system:

Airless bodies (that is, celestial bodies that do not have an atmosphere) provide access to a preserved past, allowing us to trace the origins of the Solar System, understand fundamental geological processes, and explore the origin of the materials necessary for life. Understanding the surface properties play a crucial role in constraining composition and unraveling their origin and evolution. Among these bodies are the planet Mercury, the Martian moons Phobos and Deimos, and most of the small bodies (e.g. asteroids) in the Solar System. Mercury and the moons of Mars are characterized by heterogeneous surfaces with varied and poorly understood properties.

Visible and infrared reflectance spectroscopy^*1:

The spectral properties of airless bodies allow us to obtain information about their composition. However, since these objects do not have a thick atmosphere to protect them, the data can be biased by extreme temperatures and space weathering^*2 (Fig.1). Accounting for these effects is essential when interpreting data from space missions. To quantify and correct for such biases, laboratory measurements are performed under controlled conditions.

Fig.1. From Pieters and Noble (2016). Spectra of lunar materials illustrating the spectral differences between fresh rocks (purple) and well-developped soil (red).

Spectral alteration induced by space weathering:

To investigate how temperature and irradiation modify surface spectra, I use analog samples representative of Mercury, the Martian moons, and various meteorites. These samples are subjected to controlled thermal and irradiation conditions, after which I measure the resulting spectral changes (Fig.2). I then analyze space-mission data while incorporating these experimentally constrained effects.

Fig.2. From Caminiti et al., (2024). Change in reflectance at 450 nm as a function of irradiation simulating space weathering on Mercury for a sample of komatiite (terrestrial rock analogous to the surface of Mercury).

Geological evolution of Mercury:

I developed a spectral classification for MASCS data collected by the NASA MESSENGER mission to Mercury that highlights the repartition of spectral units on Mercury (that are, regions defined by distinctive color properties). I worked with a database containing 4.7 million spectral data. I carried out an accurate study of five major impact basins on Mercury. My work has contributed to a better understanding of the stratigraphy beneath the basins and a new relative timing of volcanism. I have also proposed an evolution of deep partial melting conditions over time to explain the compositional differences associated with spectral properties in these areas. These discoveries have important implications for our understanding of effusive volcanism on Mercury and the planet's evolution over time. Spectral classification of this type will be possible on the surface of Phobos with future MMX data.

The ESA/JAXA/BepiColombo and JAXA/MMX missions:

My work involves preparing the analysis of future data from JAXA's BepiColombo and MMX missions, which will study Mercury and the moons of Mars. These missions will deliver unprecedented spectral and compositional data, offering a new window into the geological evolution of airless bodies. My laboratory work and spectral analyses contribute to building the reference frameworks needed to correctly interpret these future datasets. By combining mission observations with experimental data, we will be able to better constrain the formation, alteration, and volcanic history of Mercury, as well as the origin and evolution of Phobos and Deimos.

Terminologies

^*1 Reflectance spectroscopy : technique that identified the composition and properties of a surface by measuring how it reflects light at different wavelengths.
^*2 Space weathering : Space weathering encompasses physical and chemical processes that alter the surface of bodies without atmospheres under the influence of solar wind, micrometeorites, and cosmic radiation.