Asteroid_Impact_Seismology.jpg (259 × 383 pixels, file size: 22 KB, MIME type: image/jpeg)
Summary
editDescription | Fig. 2. Plotted below is the attenuation coefficient α as a function of the normalized critical crater diameter χ = Dcrit/D (Equation 13), where D is the asteroid diameter. Figure 2a is a plot for gravity regime scaling, and Fig. 2b is for strength regime scaling, for the specific asteroids listed in Table 1. Both plots assume nominal values for impact velocity (5 km s–1) and impactor and target density (2 g/cm3). Figure 2b assumes
strength properties typical for crater scaling in lunar regolith (Y = 105 dyn/cm2). Note the monotonic trend increasing χ with asteroid diameter, for a given α—the proposed explanation for why larger asteroids have giant craters. Circles on each plot indicate the largest undegraded crater DL observed on each asteroid, from Table 1; if DL ∼ Dcrit this provides a direct estimate for velocity attenuation α in each asteroid. As noted in the text, for gravity scaling (Fig. 2a), asteroids of low density, or otherwise suspected of being highly porous (e.g., Mathilde, Phobos, Dactyl), appear to have the lowest attenuation coefficients. Deimos has anomalously low attenuation according to the model (α = 1.17), perhaps because it is anomalously young following a global resurfacing event and has not attained critical crater equilibrium. For strength scaling (Fig. 2b), Y = 105 dyn/cm2 is adopted as a typical strength of regolith-like materials. Interestingly, for most of the larger asteroids strength scaling gives about the same derived α as gravity scaling. Asteroids as small as Itokawa and Dactyl can only sustain their largest craters in the strength regime if they have high levels of attenuation even at seismic particle velocities. |
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Author or copyright owner |
Eric Asphaug |
Source (WP:NFCC#4) | https://journals.uair.arizona.edu/index.php/maps/article/.../15592 |
Date of publication | 07 January 2008 |
Use in article (WP:NFCC#7) | Karoo (crater) |
Purpose of use in article (WP:NFCC#8) | The critical Crater Diameters of selected asteroids, including 253 Mathilde. |
Not replaceable with free media because (WP:NFCC#1) |
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The text refers to Figure 2 in the original article, and this file is Figure 2. |
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