Asteroid 87 Sylvia, known since 2001 to be part of a double system, has just gotten more interesting. A team of astronomers at the University of California at Berkeley and the Observatoire de Paris have now established that the asteroid is actually part of a triple system, the first ever discovered. Using data from the European Southern Observatory's Very Large Telescope array in Chile, the team found two small moons in nearly circular orbits. Astronomical names are always a challenge, but in this case naming comes easy. 87 Sylvia was named for Rhea Sylvia, the mother of the founders of Rome. Thus it made perfect sense for Berkeley's Franck Marchis to propose Romulus and Remus as the names of the moons. The suggestion has already been approved by the International Astronomical Union. Image: Artist's conception shows twin moonlets, Romulus and Remus, orbiting the large main-belt asteroid 87 Sylvia. Credit: European Southern Observatory. Calling them 'moons' should not obscure the fact...

The recent images from Cassini's flyby of Mimas remind us how violent the history of the early Solar System was. Now a study at the Australian National University shows that three huge asteroids -- between 20 and 50 kilometers across and traveling as a cluster -- collided with the Earth some 3.2 billion years ago. The result: volcanic eruptions, the creation of major fault lines, earthquakes and a variety of disruptive effects deep inside Earth's crust. This work grows out of evidence of extraterrestrial impact deposits from this era discovered in South Africa and extends the effects of those impacts to the Pilbara region of Western Australia. According to an ANU news release, the materials studied in the eastern Transvaal had indicated that impact craters several hundreds of kilometers in diameter had been created in oceanic parts of the Earth. In the Australian studies, the impacts coincide with the formation of fault escarpments and fault troughs and a major volcanic episode....

Can any other surface in the Solar System be this battered? The twin views below show Saturn's moon Mimas as imaged by Cassini on August 2. Note how the false-color brings out the variation across this tortured surface -- at left is an enhanced clear-filter image, at right a color composite of ultraviolet, infrared and clear-filter images. The most prominent feature in both is the 140-kilometer wide Herschel Crater, an ancient strike that is today filled with landslide material. Close study reveals numerous other craters and long grooves similar to those found on asteroids. Are these grooves related to the enormous impact that created the Herschel crater? No one knows, but study of this moon's turbulent history may help scientists understand how many impactors have moved through the Saturn system, a reminder of how dangerous a place the Solar System can be when you're in the crosshairs of an approaching piece of space debris. Mimas is a tiny place, measuring just 397 kilometers...

Over the weekend, more news came in about 2003 UB313, the soon to be renamed new planet discovered at Palomar Observatory. As discussed in astronomer Mike Brown's page on the discovery, 2003 UB313 is the largest object found orbiting the Sun since Neptune and its moon Triton in 1846. There seems to be no doubt that it is larger than Pluto and, like that planet, a member of the Kuiper Belt, a vast band of icy objects beyond Neptune. Remarkably, the 2003 UB313 team has found 80 bright Kuiper Belt objects since beginning its survey of the outer Solar System in 2001, but none so newsworthy as this one. Artist2003 UB313 takes twice as long to orbit the Sun as Pluto, and it is currently more than three times more distant, although it moves in an elliptical orbit that can bring it within Pluto's orbit and close to that of Neptune. Size limits can now be set ranging from 2210 to 3550 kilometers, depending on the nature of the surface and how it reflects light. Hubble measurements, already...