Vesta Is a Baby Planet, Not an Asteroid 107
astroengine writes "Vesta, the second largest object in the main asteroid belt, has an iron core, a varied surface, layers of rock and possibly a magnetic field — all signs of a planet in the making, not an asteroid (abstract). This is the conclusion of an international team of scientists treated to a virtual front row seat at Vesta for the past 10 months, courtesy of NASA's Dawn robotic probe. Their findings were presented during a NASA press conference on Thursday. As to why Vesta never made it to full planethood, scientists point to Jupiter. When the giant gas planet formed, nearby bodies such as Vesta found their orbits perturbed. 'Jupiter started to act like a spoon in a pot, stirring up the asteroid belt and the asteroids started bumping into one another,' said Dawn lead scientist Christopher Russell. 'If they're just out there gently orbiting and everything is going smoothly, then without Jupiter in the picture, they would gather mass and get bigger and bigger and bigger. But with Jupiter there, stirring the pot, then the asteroids start bumping into one another and breaking apart, so nothing grew in that region, but started to shrink.'"
Pluto? (Score:5, Interesting)
So Pluto was deemed just another large chunk of space debris orbiting the earth, and hence not a planet. Vesta *is* just a large asteroid amongst a whole bunch of others, but it is a planet?
I'm confused now.
Re:And it's a Good Thing (tm) (Score:5, Interesting)
Are you sure about that?
My astronomy is rusty, but I seem to recall that the inner planets are rocky because their proximity to the sun meant they were unable to build up the kind of atmosphere the gas giants did: their atmospheres boiled off before they could grow to the mammoth proportions of the gas giants.
Given the distance from the sun to Cerers, would Ceres ever have been able to form into a gas giant?
Anyway, who's to say Jupiter (or at least its moons) are lifeless? :|]
Re:Pluto? (Score:4, Interesting)
I'd rather see a definition of planet that includes Ceres and excludes Pluto than the reverse.
I don't see what would put Ceres and Pluto in different categories under any system. Neither has cleared its orbit (I too think this is a silly criterion.) Both have the hydrostatic equilibrium thing going. Both orbit the sun directly.
Well, there *is* one peculiarity about Pluto: the barycenter of the Pluto-Charon system is outside both. While I dislike the clear the neighbourhood criterion I think this system is actually the strongest proof of the current planet definition being temporary: Pluto-Charon is a binary (dwarf) planet, yet no one has bothered to even mention Charon. Instead one of our current dwarf planets orbits an empty piece of space.
Re:Pluto? (Score:5, Interesting)
No, what they have found, and what makes this newsworthy, is that Vesta's composition is much more like the terrestrials (Mercury, Venus, Earth, Luna, Mars) than what they believe Ceres' composition is. They now believe that Vesta belongs to the terrestrial family, having a silicate rock crust/mantle surrounding an iron core. Ceres, on the other hand, is probably made primarily of an ice crust/mantle with a rock core, putting it in the same family as the moons of the gas giants, and the Kuiper Belt objects like Pluto. So while Ceres and Vesta live in the same castle, they are adopted from different families.
They will know more when Dawn leaves Vesta and visits Ceres, though.