Dawn: Journey to the Asteroid Belt

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INAF: Vesta, Tell Us About the Childhood of the Solar System

Post by bystander » Sat Oct 06, 2018 3:18 am

Vesta, Tell Us About the Childhood of the Solar System
Italian National Institute for Astrophysics (INAF) | 2018 Oct 05
BetaPictDiskbMac.jpg
Artist view of a young Solar System -- Credit: NASA/FUSE/Lynette Cook
Investigating the earliest and least known phases of the history of the Solar System, when the young Sun was still enveloped by the disk of gas and dust where its planets began to form, is probably one of the most complex challenges in modern planetary science. The celestial bodies formed at the time that survived intact to now are few and in the majority of cases their "memory" of the ancient processes that marked the birth of the Solar System has been canceled or otherwise altered by the environments to which they were exposed or by the later events that shaped their evolution.

For decades the asteroid Vesta has been one of our most reliable witnesses of this ancient past: in particular, the survival of its thin volcanic crust to impacts provided a powerful constraint to how violent the Solar System was in its youth. Recently, however, the data collected by NASA’s Dawn mission, which is now coming to its end after successfully exploring also asteroid Ceres, raised the possibility that Vesta’s memory may not be as good as we thought.

On one hand, the craters produced by impacts on its surface in the last 4 billion years seem to have erased the traces of the much older ones formed in the circumsolar disk. On the other hand, the possible greater thickness of its crust with respect to what was suggested by the HED meteorites (which the Dawn mission confirmed being Vesta’s crust fragments that landed on Earth) makes the information provided by the crust survival very vague. ...

The Late Accretion and Erosion of Vesta’s Crust Recorded by Eucrites and Diogenites as an
Astrochemical Window into the Formation of Jupiter and the Early Evolution of the Solar System
~ D. Turrini et al
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PSI: Polar Wandering on Dwarf Planet Ceres Revealed

Post by bystander » Thu Oct 11, 2018 5:23 pm

Polar Wandering on Dwarf Planet Ceres Revealed
Planetary Science Institute | 2018 Oct 08
Dwarf planet Ceres experienced an indirect polar reorientation of approximately 36 degrees, a new paper by Planetary Science Institute Senior Scientist Pasquale Tricarico says.

Using data from NASA’s Dawn mission, Tricarico determined the magnitude of the reorientation with three independent and corroborating lines of evidence. Global Gravity Inversion, from a paper Tricarico published in 2013, helped determine the density variations of Ceres, especially in the crust. This is what was used to find the equatorial density anomaly. Statistical analysis of topography was used for ridge analysis and the paleo-pole. And for matching the crustal fractures, a well-proven method by Matsuyama and Nimmo was used.

“The most surprising aspect of this paper is to me the observation that the pole of Ceres must have followed an indirect path to its current pole. A multi-step reorientation could mean that the equatorial density anomaly was still evolving during the reorientation, and this could be because the crust and mantle were weakly rotationally coupled, allowing the crust to start reorienting while the mantle would lag behind,” Tricarico said. “If crust and mantle are allowed to shift with respect to one another, that could point to a layer of reduced friction between crust and mantle, and one of the possible mechanisms to reduce friction could be an ancient water ocean beneath the crust.”

True Polar Wander of Ceres Due to Heterogeneous Crustal Density ~ P. Tricarico
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
— Garrison Keillor