New Horizons co-investigator John Spencer of the Southwest Research Institute (SwRI), Boulder, CO, uses a pen to demonstrate how Ultima Thule might be rotating during a press conference prior to the flyby of the Kuiper Belt object by the New Horizons spacecraft, Monday, Dec. 31, 2018 at Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland. Photo Credit: (NASA/Joel Kowsky)