Pluto is going to be fucking heated, yo. Not
only has it been demoted to a dwarf planet, but now there’s talk of an asteroid being a planet. An asteroid! A fucking asteroid.
For years, scientists have been calling Vesta an asteroid. Granted, it’s a big asteroid – at 330 miles across, it’s the second biggest in the solar system – but NASA’s Dawn spacecraft recently got its closest look at Vesta yet, and according to Dawn’s principle investigator Christopher Russel, astronomers have been finding it hard not to refer to the asteroid as a planet.
Of course, the odds of the International Astronomical Union convening to name Vesta a planet (the same way they met in 2006 to reclassify Pluto as a dwarf planet) are basically zero. So instead, astronomers have taken to describing the massive asteroid as “transitional.” But what’s with all the confusion in the first place?
Long story short: Vesta resembles a planet. And not just any planet; Vesta is home to a lot of features typically associated with terrestrial bodies like Earth. The ratio between its topography (the elevation of its various surface characteristics) relative to its radius, for instance, is more like a rocky planet’s than an asteroid’s.
It also harbors something called impact melt, the remnants of at least one collision event so powerful, it actually liquified portions of Vesta’s surface – something never observed on an asteroid before. Researchers think that this impact melt, which would have flowed readily across Vesta’s face following an extraterrestrial collision, may explain why they’ve found no evidence of volcanic activity in the form of lava flows. Scientists are convinced that Vesta’s past was characterized by long periods of volcanism, but it’s possible that any sign of volcanic activity has been hidden by collisions and impact melt.
“[It's] because of all the impact processing over Solar System history,” explained Arizona State’s Dave Williams to BBC News. “It has destroyed all the evidence.”