Comparison of fractures generated in the laboratory (panels A and B) and observed on 67P (panels C–E). Panel A: close-up of the sample with the lowest dust fraction (10:100:300) from Fig. 3. Distinct and irregularly shaped fractures form a poorly developed network on the side wall of the sample. Panel B: enlarged section of the sample with the highest dust content (10:100:700) from Fig. 3. The length and pattern of evolving fractures are comparable to those on samples with lower dust content, but they are significantly narrower. Panel C: detailed image of fractures on the surface of 67P, taken by the Philae lander. Several irregular cracks are visible on a rough and dust-free surface. The fracture patterns correspond most closely to those on panel B. Image credit: ESA/Rosetta/Philae/CIVA. Panel D: fracture network on the surface of 67P. The fractures form a pattern of polygons with widths of up to 5 m. Panel E: evolved polygonal structures, caused by fractures on the surface of 67P. Image credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA.