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Title: A Massive Core in Jupiter Predicted From First-Principles Simulations
Authors: B. Militzer, W. B. Hubbard, J. Vorberger, I. Tamblyn, S.A. Bonev

Hydrogen-helium mixtures at conditions of Jupiter's interior are studied with first-principles computer simulations. The resulting equation of state (EOS) implies that Jupiter possesses a central core of 14-18 Earth masses of heavier elements, a result that supports core accretion as standard model for the formation of hydrogen-rich giant planets. Our nominal model has about 2 Earth masses of planetary ices in the H-He-rich mantle, a result that is, within modelling errors, consistent with abundances measured by the 1995 Galileo Entry Probe mission (equivalent to about 5 Earth masses of planetary ices when extrapolated to the mantle), suggesting that the composition found by the probe may be representative of the entire planet. Interior models derived from this first-principles EOS do not give a match to Jupiter's gravity moment J4 unless one invokes interior differential rotation, implying that jovian interior dynamics has an observable effect on the measured gravity field.

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Three Red Spots Mix it Up on JupiterThis  sequence of Hubble Space Telescope images offers an unprecedented view of a planetary game of Pac-Man among three red spots clustered together in Jupiter's atmosphere. The time series shows the passage of the "Red Spot Jr." in a band of clouds below (south) of the Great Red Spot (GRS). "Red Spot Jr." first appeared on Jupiter in early 2006 when a previously white storm turned red.

Credit: NASA, ESA, A. Simon-Miller (Goddard Space Flight Center), N. Chanover (New Mexico State University), and G. Orton (Jet Propulsion Laboratory)

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Title: A Region Void of Irregular Satellites Around Jupiter
Authors: N. Haghighipour, D. Jewitt

An interesting feature of the giant planets of our solar system is the existence of regions around these objects where no irregular satellites are observed. Surveys have shown that, around Jupiter, such a region extends from the outermost regular satellite Callisto, to the vicinity of Themisto, the innermost irregular satellite. To understand the reason for the existence of such a satellite-void region, we have studied the dynamical evolution of Jovian irregulars by numerically integrating the orbits of several hundred test particles, distributed in a region between 30 and 80 Jupiter-radii, for different values of their semimajor axes, orbital eccentricities, and inclinations. As expected, our simulations indicate that objects in or close to the influence zones of the Galilean satellites become unstable because of interactions with Ganymede and Callisto. However, these perturbations cannot account for the lack of irregular satellites in the entire region between Callisto and Themisto. It is suggested that at distances between 60 and 80 Jupiter-radii, Ganymede and Callisto may have long-term perturbative effects, which may require the integrations to be extended to times much longer than 10 Myr. The interactions of irregular satellites with protosatellites of Jupiter at the time of the formation of Jovian regulars may also be a destabilizing mechanism in this region. We present the results of our numerical simulations and discuss their applicability to similar satellite void-regions around other giant planets.

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In what's beginning to look like a case of planetary measles, a third red spot has appeared alongside its cousins the Great Red Spot and Red Spot Jr. in the turbulent Jovian atmosphere. This third red spot, which is a fraction of the size of the two other features, lies to the west of the Great Red Spot in the same latitude band of clouds.

small_web.jpg
Credit: NASA, ESA, and M. Wong and I. de Pater (University of California, Berkeley)

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Increased turbulence and storms first observed on Jupiter more than two years ago are still raging, according to astronomers from the University of California, Berkeley, and the W. M. Keck Observatory in Hawaii, who snapped high-resolution pictures of the planet earlier this month.

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Using data from the New Horizons spacesprobe,  and two telescopes on Earth, an international team of scientists have spotted one of greatest and more recent storms of the Solar system - the Small Red Spot (or LRS, for Little Red Spot) on Jupiter - which has the highest  wind  speeds  ever detected on an another  planet.
The New Horizons researchers combined the observations of their spaceprobe heading towards Pluto, which flewby Jupiter in February 2007; and data from the Hubble space telescope in orbit around the Earth, and the VLT (Very Large Telescopes) of  ESO (European Southern Observatory), perched on a mountain on the Atacama desert  in Chile.

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Scientists have observed unexpected luminous spots on Jupiter caused by its moon Io.
Besides displaying the most spectacular volcanic activity in the solar system, Io causes auroras on its mother planet that are similar to the Northern Lights on Earth. The auroral emissions linked to the volcanic moon are called the Io footprint.
From previous studies, researchers had found the Io footprint to be a bright spot that is often followed by other auroral spots. Those spots are typically located downstream relative to a flow of charged particles around the giant planet. Now, a team of planetologists from Belgium and Germany have discovered that Ios footprint can include a faint spot unexpectedly upstream of the main spot.

io spote2
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Credit ULg LPAP

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Detailed analysis of two continent-sized storms that erupted in Jupiter's atmosphere in March 2007 shows that Jupiter's internal heat plays a significant role in generating atmospheric disturbances. Understanding this outbreak could be the key to unlock the mysteries buried in the deep Jovian atmosphere. An international team coordinated by Agustin Sánchez-Lavega from the Universidad del País Vasco in Spain presents its findings about this event in the January 24 issue of the journal Nature. The team monitored the new eruption of cloud activity and its evolution with an unprecedented resolution using NASA's Hubble Space Telescope, the NASA Infrared Telescope Facility in Hawaii, and telescopes in the Canary Islands (Spain). A network of smaller telescopes around the world also supported these observations.

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This image shows an eclipse of the Sun by Jupiter, as viewed from Galileo.
Dust particles high in Jupiter's atmosphere, as well as the dust particles that compose Jupiters rings, can be seen by reflected sunlight.

Jupiter2
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Credit: (NOAO), J. Burns (Cornell) et al., Galileo Project, JPL, NASA

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