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Titan’s internal structure and the evolutionary consequences
Fortes, A. D.
Titan’s moment of inertia (MoI), estimated from the quadrupole gravity field measured by the Cassini spacecraft, is 0.342, which has been interpreted as evidence of a partially differentiated internal mass distribution. It is shown here that the observed MoI is equally consistent with a fully differentiated internal structure comprising a shell of…
Two Extrasolar Asteroids with Low Volatile-element Mass Fractions
Koester, D.; Zuckerman, B.; Xu, S. +2 more
Using ultraviolet spectra obtained with the Cosmic Origins Spectrograph on the Hubble Space Telescope, we extend our previous ground-based optical determinations of the composition of the extrasolar asteroids accreted onto two white dwarfs, GD 40 and G241-6. Combining optical and ultraviolet spectra of these stars with He-dominated atmospheres, 13…
Dynamics of the Solar Magnetic Bright Points Derived from Their Horizontal Motions
Chitta, L. P.; Kariyappa, R.; van Ballegooijen, A. A. +2 more
The subarcsecond bright points (BPs) associated with the small-scale magnetic fields in the lower solar atmosphere are advected by the evolution of the photospheric granules. We measure various quantities related to the horizontal motions of the BPs observed in two wavelengths, including the velocity autocorrelation function. A 1 hr time sequence …
Active upper-atmosphere chemistry and dynamics from polar circulation reversal on Titan
Vinatier, Sandrine; Nixon, Conor A.; Irwin, Patrick G. J. +6 more
Saturn's moon Titan has a nitrogen atmosphere comparable to Earth's, with a surface pressure of 1.4 bar. Numerical models reproduce the tropospheric conditions very well but have trouble explaining the observed middle-atmosphere temperatures, composition and winds. The top of the middle-atmosphere circulation has been thought to lie at an altitude…
AKARI observations of ice absorption bands towards edge-on young stellar objects
Tamura, M.; Kandori, R.; Pontoppidan, K. M. +9 more
Context. Circumstellar disks and envelopes of low-mass young stellar objects (YSOs) contain significant amounts of ice. Such icy material will evolve to become volatile components of planetary systems, such as comets in our solar system.
Aims: To investigate the composition and evolution of circumstellar ice around low-mass young stellar obje…
Transmission Electron Microscopy of CONCORDIA UltraCarbonaceous Antarctic MicroMeteorites (UCAMMs): Mineralogical properties
Engrand, C.; Rouzaud, J. -N.; Duprat, J. +2 more
We performed mineralogical and petrographic studies of three UltraCarbonaceous Antarctic Micrometeorites (UCAMMs) by analytical transmission electron microscopy (TEM). The UCAMMs were identified in the CONCORDIA micrometeorite collection (2002 and 2006) recovered from central Antarctic snow, and are of probable cometary origin. UCAMMs are dominate…
Global maps of anhydrous minerals at the surface of Mars from OMEGA/MEx
Bibring, J. -P.; Gondet, B.; Langevin, Y. +7 more
We here reassess the global distribution of several key mineral species using the entire OMEGA/Mars Express VIS-NIR imaging spectrometer data set, acquired from orbit insertion in January 2004 to August 2010. Thirty-two pixels per degree global maps of ferric oxides, pyroxenes and olivines have been derived. A significant filtering process was app…
On the effects of clouds and hazes in the atmospheres of hot Jupiters: semi-analytical temperature-pressure profiles
Sing, David K.; Heng, Kevin; Pont, Frédéric +1 more
Motivated by the work of Guillot, we present a semi-analytical formalism for calculating the temperature-pressure profiles in hot Jovian atmospheres which includes the effects of clouds/hazes and collision-induced absorption. Using the dual-band approximation, we assume that stellar irradiation and thermal emission from the hot Jupiter occur at di…
LoCuSS: A Dynamical Analysis of X-Ray Active Galactic Nuclei in Local Clusters
Finoguenov, A.; Smith, G. P.; Okabe, N. +7 more
We present a study of the distribution of X-ray active galactic nuclei (AGNs) in a representative sample of 26 massive clusters at 0.15 < z < 0.30, combining Chandra observations sensitive to X-ray point sources of luminosity LX ~ 1042 erg s-1 at the cluster redshift with extensive and highly complete spectro…
The location of reconnection at the magnetopause: Testing the maximum magnetic shear model with THEMIS observations
Fuselier, S. A.; Phan, T. D.; Trattner, K. J. +1 more
Reconnection at the Earth's magnetopause is the mechanism by which magnetic fields in different regions change topology to create open magnetic field lines that allow energy and momentum to flow into the magnetosphere. One of the long-standing open questions about magnetic reconnection is the location of the reconnection line. There are two reconn…