Saturn’s tidal pull explains cryovolcanism on Enceladus
The Cassini spacecraft was launched in 1997 with the aim of studying the Saturn system. The satellite arrived at Saturn on 1 July 2004 and conducted a range of experiments to determine the temperature, mass, structure and chemical composition of Saturn, its rings and moons using ultraviolet, optical and near-infrared remote-sensing instruments. The initial 4-year mission ended in June 2008, which was followed by a 2-year extended mission called the Cassini Equinox Mission. Cassini is now in its second extended mission called the Cassini Solstice Mission.
Astronomers were amazed in 2005 during a Cassini flyby of Enceladus when cryovolcanoes, which are icy water jets resembling geysers on Earth, were detected in the southern polar region of the satellite emerging from long surface fissures known as “tiger stripes”. Subsequent observations also detected complex organic compounds in the spray, which is very exciting from an astrobiological perspective. Tidal heating from Saturn keeps Enceladus relatively warm and “hotspots” have been found in the tiger stripes at the locations of the cryovolcanoes.
Terry Hurford and collaborators suggested that the gravitational interaction of Enceladus with Saturn produces tidal deformations (like the tides produced on Earth by the Moon), which cause stresses and hence deformations of the surface of Enceladus resulting in the tiger stripes fissures. Hurford et al. have now been able to correlate the tidal stresses with the icy jet activity and show that the greatest stresses act on the tiger stripes near apocentre of Enceladus’s eccentric orbit around Saturn.
These new results were presented this week at the Lunar and Planetary Science Conference at The Woodlands, Texas. For more details, see
- Cassini Sees Saturn Stressing out Enceladus, Casini website
- Tidal Control of Jet Eruptions Observed by Cassini ISS, Hurford et al. (2012), LPI, 43, 2154
- Cassini Solstice Mission, JPL website
- 43rd Lunar and Planetary Science Conference, 19-23 March 2012 (including links to Livestream and recorded presentations)