An article published in the journal “Monthly Notices of the Royal Astronomical Society” reports a study indicating that the interior of the nucleus of comet 67P/Churyumov-Gerasimenko is porous and less dense than its surface. A team of researchers reviewed data collected by ESA’s Rosetta space probe and its Philae lander’s CONSERT instrument. The signals exchanged between them through the cometary nucleus propagated at different speeds, indicating a varying density of its interior. This suggests that solar radiation changed the surface, making it less porous.