Some claim to know that there are volcanoes on comets without evidence for an internal heat source. No spacecrafts have ever imaged comets with volcanoes. According to NASA scientists : Cryo or other volcanoes occur on Jupiters moon Io and the Saturn moon Enceladus which both have internal heat sources.
NASA’s Rosaly Lopes and the U.S. Geological Survey’s Astrogeology Science Center’s Randy Kirk explain the phenomenon of cryovolcanism.

Sun distance (au): 6,17 Perihel 28.March 2019 Sun dist.(au): 5,77

Time: 00:30UT 2024-01-16 Exp. 40 X 65sec
Tel: 0.254m f/7.3 ST-10XME CCD 2x2bin 1.5"/pix
Odd Trondal Obs.code 238 (Uranium). Oslo Norway