Hubble finds evidence that comet 41P reversed its spin

In March 2026, NASA reported evidence that comet 41P/Tuttle-Giacobini-Kresák had slowed its rotation and then spun up in the opposite direction. After a 2017 pass around the Sun, Swift observations measured a rotation period of 46–60 hours; later Hubble images indicated about 14 hours. The researchers’ simplest explanation is that jets of escaping gas kept pushing against the original rotation until the comet nearly stopped and reversed. Those jets can act like small thrusters, showing how a comet’s own activity can change its motion.