Space Data's Dr. Ryuki Hyodo Explores Hypervelocity Impact Phenomena of Micrometeoroids Through 3D Simulation

Space Data, Inc. (Headquarters: Minato-ku, Tokyo; President and CEO: Koyo Sato; hereinafter "Space Data") is pleased to announce that a paper authored primarily by Dr. Ryuki Hyodo (concurrently a university faculty member in planetary science/AI science), Chief Science Officer (CSO), was published online in the international academic journal "Earth and Planetary Science Letters" on June 20, 2026. This research focuses on the phenomenon of "hypervelocity impacts," which occur universally in space, and uses world-class 3D impact simulations to visualize and analyze in detail the process of hypervelocity collisions between rocky micrometeoroids and icy celestial bodies at speeds of 30 km/s. The results revealed that the porosity (degree of internal void space) of both the impactor (meteoroid) and the target significantly influences the crater formation process and the extent of heating and vaporization caused by the impact.

Background: The Ubiquitous Phenomenon of "Hypervelocity Impacts" in Space

Celestial impacts are one of the most fundamental phenomena in the universe, gradually reshaping the topography, composition, and thermal state of planetary surfaces over time. In particular, the solar system is filled with countless "micrometeoroids" derived from asteroids, comets, and Kuiper Belt Objects – "cosmic dust" ranging from a few microns to sub-millimeters in size. In the outer solar system, micrometeoroids drawn by the strong gravity of planets collide at hypervelocities of 10-100 km/s with the surfaces of bodies such as rings and moons.

It has been thought that in such hypervelocity impacts, the impactor is instantly subjected to a strong shock wave, heating, melting, and vaporizing, leading to the ejection of high-temperature vapor and molten particles. However, how this impact phenomenon "actually proceeds, what pressures and temperatures the impactor experiences," and especially how differences in the porosity of the impactor and target influence the outcome, have not been well understood at the scale of micrometeoroids. While many micrometeoroids are rocky (non-icy), target bodies are often icy, and since both can have significantly different porosities, the progression of impacts is expected to vary.

This research primarily considers Saturn's rings, which are also attracting attention as a candidate target for Japan's next-generation exploration plan. Hypervelocity impacts reaching approximately 30 km/s are thought to occur frequently in Saturn's rings. Saturn's rings are "polluted" by non-icy micrometeoroids falling from outside, and the degree of this pollution has been used as a clue to estimate the age of the rings. Therefore, accurately understanding "what actually happens" when infalling micrometeoroids interact through the "impact phenomenon" is an essential first step in deciphering the evolution of the surfaces of celestial bodies, including Saturn's rings.

Research Overview: What Happens to Micrometeoroids in Hypervelocity Impacts?

Dr. Ryuki Hyodo, who led this research, is an expert in impact phenomena and has been working on the challenging problem of the origin of Saturn's rings for over 10 years. He currently serves as Chief Science Officer (CSO) at Space Data, while also engaging in research and education as an Associate Professor at the Earth-Life Science Institute, Tokyo Institute of Technology, and the Graduate School of Artificial Intelligence Science, Rikkyo University. This latest achievement is a continuation of his long-standing research.

The research group used the world-class 3D impact simulation code "iSALE-3D" to simulate, at ultra-high resolution, the process of a rocky (dunite) micrometeoroid colliding obliquely (at 45 degrees) with an icy target at 30 km/s. Furthermore, by independently varying the porosity of the meteoroid and the target (combinations ranging from 0% porosity, i.e., no voids, to 90% porosity, i.e., extremely void-rich), they investigated the crater formation immediately after impact and the maximum pressure and temperature experienced by the meteoroid. In parallel, they newly constructed a semi-analytical model (a simplified predictive model based on equations) to physically interpret the calculation results, transparently showing how the impact energy is distributed between "material compression" and "void collapse (irreversible dissipation)."

3D impact simulations with varying combinations of target and meteoroid porosity (impact velocity 30 km/s, impact angle 45 degrees, meteoroid radius 10 μm). Colors represent temperature. The figure shows how the immediate post-impact state varies dramatically depending on the porosity combination, ranging from elongated cavities that penetrate deeply to explosive vapor expansion near the surface. (Source: Hyodo et al. 2026, Earth and Planetary Science Letters / CC BY 4.0)

Main Findings

1. Crater shape immediately after impact changes dramatically with porosity combinations.

When a non-porous meteoroid impacts a highly porous (90%) icy target, the meteoroid penetrates deeply into the target, creating an elongated cavity filled with high-temperature vapor.

Conversely, when a highly porous (90%) meteoroid impacts a non-porous icy target, it penetrates very little, and high-temperature vapor reaching 10,000 degrees Celsius explosively expands near the surface.

When the porosities of both are similar, the resulting crater is intermediate, more like a hemisphere.

2. Maximum pressure and temperature experienced by the meteoroid vary by about an order of magnitude depending on porosity.

Higher porosity (more voids) leads to more impact energy being consumed in collapsing the voids (irreversible dissipation), weakening the shock pressure transmitted to the meteoroid. As a result, the maximum pressure and temperature experienced by the meteoroid were found to vary by nearly a factor of 10 depending on the porosity combination.

3. Nevertheless, at high impact speeds of 30 km/s, rocky micrometeoroids "almost certainly" evaporate.

Despite such large variations in maximum pressure and temperature, rocky micrometeoroids were shown to be efficiently heated and vaporized regardless of the porosity combination of the meteoroid and target. Furthermore, in cases where the meteoroid penetrates deeply into a porous icy target, it was also revealed that the meteoroid reaches high temperatures through heat exchange with high-temperature water vapor generated from the target side, even without directly experiencing strong impact.

Significance of These Findings: Implications Beyond Saturn for Impact Phenomena in Space

The significance of these findings lies in consistently clarifying that "the internal structure of matter, specifically porosity, governs the outcome of hypervelocity impact phenomena," from crater formation to shock heating and vaporization. By quantitatively demonstrating, through both numerical calculations and a newly developed semi-analytical model, how impact energy is partitioned between material compression and irreversible heating due to void collapse, a step forward has been made in the universal understanding of hypervelocity impact phenomena.

These insights are directly relevant to the formation of Saturn's rings. Previously, it was often implicitly assumed that non-icy micrometeoroids falling from outside would "simply" contaminate the rings. However, this research shows that these contaminating micrometeoroids almost entirely evaporate through the impact process. This means that micrometeoroids are not incorporated into the rings in their original form but remain only after undergoing significant thermodynamic and chemical processes such as vaporization, condensation, and chemical changes. This result is consistent with research published by Dr. Hyodo and colleagues in "Nature Geoscience" in 2025 regarding the "pollution resistance" of Saturn's ring particles. It also suggests that differences in the porosity of ring particles can influence the amount of vapor produced and the dissipation of energy during impacts.

Furthermore, such hypervelocity impacts are not limited to Saturn but occur universally on the surfaces of many celestial bodies, including in the outer solar system, gradually altering their surface structure, composition, and thermal state over long periods. The knowledge gained from this study on "the progression of impact phenomena and the role of porosity" can be broadly extended to understanding impacts and surface evolution in various planetary environments beyond Saturn.

Future Prospects

While this study focused on the impact of rocky meteoroids onto icy targets, the research group plans to expand their research to the inverse case of icy meteoroids impacting rocky targets, as well as to a wider range of impact velocities, porosities, and compositions. They also intend to leverage these findings to utilize and upgrade Space Data's AI platform for space, "SpaceBrain," which comprehensively monitors, analyzes, and predicts threats in space, thereby connecting research with products.

Driven by the vision of "a society where space can be utilized by anyone," Space Data advocates for the democratization of space, aiming to realize a society where everyone can access and understand space. Fundamental research like this leads to a deeper understanding of phenomena occurring in space. Space Data will continue to deliver the results of research that tackles fundamental questions about space to society.

Publication Information

Journal: Earth and Planetary Science Letters (Published online June 20, 2026)

Paper Title: Numerical simulations of hypervelocity micrometeoroid impacts: Rocky impactors onto icy targets and the role of porosity

Authors: Ryuki Hyodo (Space Data, Inc. / Earth-Life Science Institute, Tokyo Institute of Technology / Graduate School of Artificial Intelligence Science, Rikkyo University / Université Paris Cité), Shigeru Wakita (Purdue University), Brandon C. Johnson (Purdue University)

DOI: 10.1016/j.epsl.2026.120179

URL: https://doi.org/10.1016/j.epsl.2026.120179

*This paper is published open access (CC BY 4.0) and is available to the public.

*This press release provides an easy-to-understand explanation of the research findings for the general public. For detailed technical information and prerequisites, please refer to the original paper.

About Space Data, Inc.

Space Data, Inc. is a technology startup that creates new industries and social infrastructure by fusing space and digital technology, driven by the vision of "a society where space can be utilized by anyone."

Utilizing digital twin technology that precisely reproduces Earth and space environments, the company aims to build digital platforms that support the future, from space to urban development, disaster prevention, and national security. Furthermore, through the development of operational infrastructure for space robots and space stations, they are working towards the realization of a space society.

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