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. 2025 Aug 22;11(34):eadx0294.
doi: 10.1126/sciadv.adx0294. Epub 2025 Aug 20.

The origin of complex crater formation during high-speed impacts

Hasan F Celebi  1 , Austin J Andrews  1 , Ioannis Pothos  2 , Nathan A Bellefeuille  2 , Bernard A Olson  1 , Thomas E Schwartzentruber  2 , Christopher J Hogan  1
Affiliations

The origin of complex crater formation during high-speed impacts

Hasan F Celebi et al. Sci Adv. .

Abstract

Complex crater formation is an incompletely understood phenomenon, referring to instances wherein a high-speed projectile impacts a surface and leaves a crater characterized by a central uplift. We elucidate the mechanism of complex crater formation by examining crater formation on different polymer substrates resulting from microparticle impacts with tunable microparticle diameter (1.8 to 6.1 micrometers) and impact velocities up to 840 meters per second. Central uplift is uniquely observed in craters on amorphous polymers, with the degree of complexity directly linked to the polymer thermal properties and homogeneity. We demonstrate that the complex crater volume scales with the ratio of the specific kinetic energy of the impacting object to the specific energy required to raise the impacted substrate to its glass transition temperature (the Eckert number). Our results also confirm that complex crater formation can occur not only for macroscopic celestial collisions but also during sufficiently high velocity collisions at the micrometer scale.

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Figures

Fig. 1.
Fig. 1.. Isometric 3D reconstructions of AFM measurements of craters generated by high-speed FeSO4 microparticle impact on different materials.
(A) PTFE, (B) nylon 66, (C) PP, (D) ABS, (E) PS, (F) PEI, (G) PC, (H) PMMA, and (I) PVC. For all images, the impact angle was 90°, the working gas was helium, the particle diameter was 1.8 μm, and the impact speed was 840 m s−1.
Fig. 2.
Fig. 2.. Crater topographies on PC samples for different impact angles.
(A) 90°, (B) 75°, (C) 60°, and (D) 45° FeSO4 impacts. (Top row) 3D reconstructions from AFM measurements. (Middle row) Contour plots. (Bottom row) Crater profiles along a single axis aligned horizontally in the middle of the planes shown in the middle row images. Working gas: helium. Particle diameter: 1.8 μm. Particle speed: 840 m s−1. Impact directions are indicated with arrows.
Fig. 3.
Fig. 3.. Crater topographies on PMMA samples for different impact angles.
(A) 90°, (B) 75°, (C) 60°, and (D) 45° FeSO4 impacts. (Top row) 3D reconstructions from AFM measurements. (Middle row) Contour plots. (Bottom row) Crater profiles along a single axis aligned horizontally in the middle of the planes shown in the middle row images. Working gas: helium. Particle diameter: 1.8 μm. Particle speed: 840 m s−1. Impact directions are indicated with arrows.
Fig. 4.
Fig. 4.. Cavity depth scaling with crater complexity.
Crater cross-sectional profiles along a single axis for different impact angles and velocities: (A) 90° and 520 m s−1, (B) 90° and 840 m s−1, (C) 45° and 520 m s−1, and (D) 45° and 840 m s−1. (E) Cavity maximum depth variation with respect to the particle velocity normal to the surface. Letters correspond to the conditions on the left. Circle: 90°; square: 75°; triangle: 60°; diamond: 45° impact angle. The percentage of crater complexity is represented by a green background. Particle diameter: 1.8 μm. Error bars represent the standard deviation over 5 to 10 individual craters per examined condition.
Fig. 5.
Fig. 5.. Effect of particle kinetic energy on crater dimensions.
Crater cross-sectional profiles for different-sized particle impacts on (A) PEI, (B) PC, and (C) PVC targets. Lines with lighter shades and wider dots represent larger particle sizes. (D) Cavity diameter and (E) total displaced volume variation relative to particle kinetic energy for different materials. PEI: orange; PC: black; PMMA: blue; PVC: purple. The green solid lines represent the particle diameter and volume for the impacts examined, showing that the craters are smaller than the impacting particles under all conditions.
Fig. 6.
Fig. 6.. Crater scaling for amorphous polymers with observed crater complexity.
(A) Crater complexity percentage variation with respect to the inverse thermal scaling parameter. Logarithmic scaling of the plot is shown in the inset. (B) Cratering efficiency variation with respect to the strength-scaled size. Crater measurements on aluminum and copper targets, as reported by Andrews et al. (42, 43), are represented in the data with crosses and stars, respectively. Orange: PEI; black: PC; blue: PMMA; purple: PVC substrate. Circle: 90°; square: 75°; triangle: 60°; diamond: 45° impact angle.
Fig. 7.
Fig. 7.. Postimpact analysis for crater sizing.
(A) AFM scanning. (B) Volume dissection generated by a computer program. (C) Crater dimensions labeled for normal and angled impacts.
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References

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