Peculiarly, the researchers couldn't see any dust on Ryugu's rocks, which all clocked in at between four inches to one foot across. Small dust particles should be present thanks to frequent bombardment of micrometeorites and weathering, but it was nowhere to be found. "As the asteroid has very low gravity, only one-sixtieth of that experienced on Earth's surface, the dust has either disappeared into cavities on the asteroid or has escaped into space," lead author Ralf Jaumann said in a German Aerospace Center press release. The team is still puzzling out the physical mechanism behind this unexpected dust behavior.