Fig. 7: The thermal fractures on Dimorphos’ boulders may have developed in less than 100,000 years.

a Cumulative distribution of the length a_x of the horizontally propagating fractures in a boulder of thermal inertia 370 J s^−1/2 m⁻² K⁻¹ and b of thermal inertia 1000 J s^−1/2 m⁻² K⁻¹. The fractures’ initial size-frequency distribution resembles that of microcracks observed in meteorites and evolved to become similar in slope to that of the host boulders and the measured fractures in 10–100 kyr. This time is likely an upper limit because we neglect microscopic stress between elements of the rocks and the effect of eclipses (“Methods” section). The black curves correspond to the average of propagation at aphelion and perihelion with a 3:1 weight. We adopt the material properties in Table 1.