Here’s a video of the spinning, courtesy of NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute:
Earth was born wet, a new study of moon rocks finds.
Although there is wide consensus on the theory that the moon formed through the collision of Earth and another object, the specifics of that theory are still not certain. And two new papers published in Science present two new significantly different takes on those specifics.
Saturn’s moon Enceladus has been known to have an underground ocean since 2005, and now astronomers are looking to Ariel, one of Uranus’ moons, as another possible locale with an underground oasis. From my Nature blog post, Could a moon of Uranus harbour an underground ocean?:
Saturn’s moon mix—different locations, different densities, some are ice, others rocky—begs the question how did they form. Current research by Erik Asphaug and Andreas Reufer provide a possible answer:
According to a model proposed by Erik Asphaug, a planetary scientist at the University of California, Santa Cruz, and his colleague Andreas Reufer of the University of Bern in Switzerland, Saturn and its satellites initially resembled a miniature version of the Jupiter system, with four large satellites similar in size to Jupiter’s Galilean moons. Saturn’s satellites then began to merge, eventually forming Titan, the planet’s largest moon, says Asphaug, who presented the model on 17 October at the annual meeting of the American Astronomical Society’s Division for Planetary Sciences in Reno, Nevada.
The mid-size satellites would have formed from the scraps left over from building Titan, with the mergers perhaps accounting for Titan’s surprisingly elongated orbit. The merging may have been triggered by an instability in the Solar System about 3.8 billion years ago, when theorists think that the orbits of Uranus and Neptune were migrating. Because of Jupiter’s bigger gravitational grip, its moons were relatively impervious to the disturbance, Asphaug speculates.
The model isn’t without its critics, though. For a video explaining the model, and details about some of the models’ issues, read my Nature article Moon-merge model could explain Saturnian system.
My latest article is about new research that adds to the uncertainty of how the Moon was formed by looking at the Moon’s isotopic composition:
Question over theory of lunar formation
A chemical analysis of lunar rocks may force scientists to revise the leading theory for the Moon’s formation: that the satellite was born when a Mars-sized body smacked into the infant Earth some 4.5 billion years ago.
If that were the case, the Moon ought to bear the chemical signature of both Earth and its proposed ‘second’ parent. But a study published today in Nature Geoscience1 suggests that the Moon’s isotopic composition reflects only Earth’s contribution.