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Cryovolcanoes on Ceres 

It’s been a little while since the Dawn probe imaged those mysterious ‘lights’ in the craters of the dwarf planet Ceres (1).  On first impression, these seem to be impact marks where brighter materials lying below the surface were exposed following meteoritic bombardment.  But they are uncommonly bright for an asteroid, so speculation about the nature of the materials involved has been rife in the planetary science community, and what it could mean for how the dwarf planet formed in the first place (2).  The bright spots, now widely thought to be salt deposits, have recently even been given names:

“The two most famous bright spots on Ceres have been given names. These once-mysterious spots are now thought by most scientists to be salt deposits. They’re now called Cerealia Facula (for the brighter of the two spots) and Vinalia Faculae (for the cluster of less reflective spots to the east). Both names are related to ancient Roman festivals.” (3)

ceres_lights

But that’s not the only mystery on Ceres.  There is a growing consensus that there may be geophysical processes going on that are relatively recent (at least in terms of geological time periods): Read More…

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Early Solar System Catastrophism

The two moons of Mars have always presented planetary scientists with something of a mystery. These tiny moons, Phobos and Deimos, whizz around Mars at no great height at all: Phobos whips around the red planet in less than 8 hours, at a height of only 3,700 miles – the closest of any moon to its parent planet. I say ‘parent’ advisedly because a new theory of the origin of these peculiar little moons suggests that they emerged from a major impact between mars and a dwarf planet. It has generally been assumed that they were captured asteroids, but the relative circularity of their orbits argued against such a capture. Work on the possibility of a catastrophic origin was carried out last year by two separate teams of researchers, after decades of battling intense scepticism within the scientific community (1). An important finding of the modelling at that time was that the resultant debris would circulate around the red planet at a relatively low altitude, which is in keeping with the orbits of the two extant moons.
More recently, further computer modelling of various impact scenarios carried out by one of those teams has narrowed down the range of masses of an impactor to about the size of Pluto. The resultant debris field was initially far more extensive than the two moons left today:
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