Scientists have been puzzled by periodic bursts of radiation, known as the Saturn kilometric radiation (SKR), that occur in the planet’s magnetosphere. These emissions occur at a rate that is close to, but not quite the same as, the rate at which the planet rotates.

New observations from the Cassini spacecraft’s flybys of Saturn’s moon Enceladus in 2008 are revealing new details about the plasma environment around Enceladus and how it may affect Saturn’s magnetosphere. These observations could also shed some light on the SKR rotation rate.

Enceladus sprays out a plume of water vapor and ice from its south pole. This plume produces ionized gas that is a significant source of plasma for Saturn’s magnetosphere and E ring. Observations described by Morooka et al. show that the plume also produces negatively charged dust that affects the motion of the plasma in this region. This dust-plasma interaction impacts the dynamics of Saturn’s magnetosphere, possibly influencing the rate of SKR emissions.

Source: Journal of Geophysical Research-Space Physics, doi:10.1029/2011JA017038, 2011 http://dx.doi.org/10.1029/2011JA017038

Title: Dusty plasma in the vicinity of Enceladus

Authors: M. W. Morooka, J.-E. Wahlund, and A. I. Eriksson: Swedish Institute of Space Physics, Uppsala, Sweden; W. M. Farrell: Planetary Magnetospheres Laboratory, Goddard Space Flight Center, Greenbelt, Maryland, USA; D. A. Gurnett, W. S. Kurth, and A. M. Persoon: Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa, USA; M. Shafiq, M. Andre, and M. K. G. Holmberg: Swedish Institute of Space Physics, Uppsala, Sweden.

EVALUATING THE ENERGY BALANCE OF SATURN’S MOON TITAN

To understand the weather and climate on Earth as well as on other planets and their moons, scientists need to know the global energy balance, the balance between energy coming in from solar radiation and thermal energy radiated back out of the planet. The energy balance can provide interesting information about a planet. For instance, Jupiter, Saturn, and Neptune emit more energy than they absorb, implying these planets have an internal heat source. Earth, on the other hand, is in near equilibrium, with energy coming in approximately equaling energy going out, though a small energy imbalance can lead to global climate change.

Saturn’s moon Titan is the only moon in the solar system with a thick atmosphere, and scientists have been interested in exploring ways in which Titan is similar to Earth. To learn more about Titan, Li et al. calculated its energy balance. The absorbed energy has been measured by various telescopes and spacecraft; the emitted energy was recently measured by instruments onboard NASA’s Cassini spacecraft. The authors compared total absorbed solar power with total emitted thermal power and find that the global energy budget of Titan is in equilibrium within the measurement error.

Source: Geophysical Research Letters, doi:10.1029/2011GL050053, 2011 http://dx.doi.org/10.1029/2011GL050053

Title: The global energy balance of Titan

Authors: Liming Li, Mark A. Smith, and Xun Jiang: Department of Earth and Atmospheric Sciences, University of Houston, Houston,Texas, USA; Conor A. Nixon and Richard K. Achterberg: Department of Astronomy, University of Maryland, College Park, Maryland, USA; Nicolas J. P. Gorius, Amy A. Simon-Miller, and F. Michael Flasar: NASA Goddard Space Flight Center, Greenbelt, Maryland, USA; Barney J. Conrath and Peter J. Gierasch: Department of Astronomy, Cornell University, Ithaca, New York, USA; Kevin H. Baines, Robert A. West, and Ashwin R. Vasavada: Jet Propulsion Laboratory, Caltech, Pasadena, California, USA; Andrew P. Ingersoll and Shawn P. Ewald: Division of Geological and Planetary Sciences, Caltech, Pasadena, California, USA.