Artistic representation of the asteroid-belt between Mars and Jupiter in the solar system. Credit: mopic/shutterstock

Cohesive force of particles. (A) Measured cohesive force of Allende and Tagish Lake meteorite fragments, prepared by a mortar and pestle or projectile impact, against a smooth glass slide under ambient conditions. The fitted curves were obtained on the basis of Eq. 3 in the article. (B) Measured cohesive force of tens-of-micrometer– and micrometer-sized Allende fragments against a stainless steel slide under ambient conditions. The value of the large fragments is approximately twice greater than that against the glass slide in (A), which might be consistent with the trend that the Hamaker constant of metals is greater than that of silica. (C) Schematic diagram of the contact states of meteorite fragments of different sizes against slides inferred from the cohesive-force measurements. The left fragment represents tens-of-micrometer–sized fragments at 1 gE, the middle fragment represents micrometer-sized fragments at 1 gE, and the right fragment represents micrometer-sized fragments at 8 × 104 gE. (D) Comparison of the measured cohesive force of aggregates tens of micrometers in size consisting of submicrometer-sized silica spheres against a glass slide under ambient conditions and the cohesive force estimated by the relationship obtained for the micrometer-sized silica spheres based on the size distribution of the constituent spheres. Solid curve indicates measurements, dashed curve indicates predictions, and thin dotted curve indicates three times the prediction. Credit: Science Advances (2023). DOI: 10.1126/sciadv.add3530

Cohesive forces of meteorite fragments and abundance of matrix in the meteorites. Open symbols and dashed error bars indicate measurements under ambient conditions. The Tagish Lake and Allende meteorite values were obtained in this study; all other values are based on a previous study. The cohesive force per contact point between particles was corrected by one-half [because values obtained using the centrifugal method were measured between a particle and a slide] and one-third (because particles of tens of micrometers in size were in contact with a slide at approximately three points). Matrix abundance values were obtained from previous studies. Plots and error bars represent typical values and the range of the cumulative number fraction corresponding to 0.25 to 0.75, calculated by fitting Eq. 3 to the measurements, respectively. Closed symbols and solid error bars represent cohesive forces 3.5-fold greater than those measured under ambient conditions. The values are summarized in Table 1. Credit: Science Advances (2023). DOI: 10.1126/sciadv.add3530

Low cohesive force and high surface mobility of asteroid particles. (A) Comparison of gravity and cohesive forces acting on particles on the surfaces of C- and S-type asteroids with a diameter of 0.5 km. Dashed lines indicate gravity. Gray solid line indicates a cohesive force proportional to particle size. Blue and red solid lines indicate threefold those of typical cohesive forces per contact point listed. We assumed that typical cohesive forces for C- and S-type asteroids were the averages for carbonaceous and ordinary chondrites, respectively. Filled areas represent the predicted range of the cohesive force for particles with averaged typical cohesive forces. The range of the cohesive force corresponding to a cumulative number fraction of 0.25 to 0.75 was approximately 0.28 to 1.5 times the typical cohesive force on average. Dotted lines indicate the predicted cohesive forces, considering plastic deformation due to the particle's weight. (B) Pressure required to overcome gravity and cohesive force. Dashed curves indicate the case of the cohesive force proportional to the particle size. Solid curves indicate the case of the cohesive force obtained in this study. Credit: Science Advances (2023). DOI: 10.1126/sciadv.add3530

Microscopic morphology of particle. (A) Surface morphologies of each type of sample particle acquired via confocal laser scanning microscopy, and (B) one-dimensional profile extracted from the data. The horizontal axis shows the location along a line perpendicular to the line of sight, and the vertical axis shows the height. Data for the Allende ground fragment and silica sand particle are from a previous study. Credit: Science Advances (2023). DOI: 10.1126/sciadv.add3530

Configuration of cohesive force measurements under reduced pressure. (A) Schematic diagram of centrifugal force application under reduced pressure. The cohesive force of particles was measured under reduced pressure in a space enclosed by a glass slide and a valved mini-vacuum chamber. (B) Particle heating was performed by placing a glass slide with particles in contact with a hot plate. (C) Optical microscope images of Allende fragments after heating (250 ℃) and evacuation (~10−3 Pa) for 48 h on a slide before and after applying centrifugal accelerations of 10, 1020, and 103gE. Scale bar is 100 µm. (D) Configuration for optical microscope image acquisition. Micrometers were used to adjust the glass slide to acquire images of the same location. A light-emitting diode (LED) ring was used for imaging particles attached to the inner surface of the glass slide. Credit: Science Advances (2023). DOI: 10.1126/sciadv.add3530