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Could giant asteroid Vesta actually be a planet?
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.”
The Dawn spacecraft is scheduled to continue orbiting Vesta until July of this year, when it will set a course for Ceres, the largest asteroid in the Solar System. Ceres is significantly larger than Vesta; at close to 600 miles in diameter, it actually qualifies as the smallest of the dwarf planets. It’ll be very interesting to see if its surface features are as stereotypically “planet-like” as Vesta’s.
Read more about Dawn’s latest views of giant asteroid Vesta over on BBC News.
Top image via NASA](http://24.media.tumblr.com/tumblr_m1dd38lPjm1qbkzabo1_1280.jpg)
If you were to visit Earth at most points in its history, it wouldn’t look that different. The continents might be rearranged, but you would still recognize our planet as that familiar pale blue dot. But until about 2.45 billion years ago, Earth was locked in a constant cycle of flipping between clear skies and this hydrocarbon smog. Earth’s atmosphere would have looked much like that of Saturn’s moon Titan, which is also covered in a methane fog.
This theory of Earth’s atmospheric past has been around for a while, but it’s only now that an international team of researchers have been able to find definitive proof. By analyzing sediments found in South Africa dating back 2.5 to 2.65 billion years, the team were able to reconstruct the unique atmospheric cycle that then dominated the planet. Writing in Nature Geoscience, they explain the strange push-pull that governed the skies of the early Earth:
We find evidence for oxygen production in microbial mats and localized oxygenation of surface waters. Carbon and sulphur isotopes indicate that this oxygen production occurred under a reduced atmosphere that was periodically rich in methane, consistent with the prediction of a hydrocarbon haze. Our simulations predict transitions between two stable atmospheric states, one with organic haze and the other haze-free. The transitions are presumably governed by variations in the amount of biological methane production during the Archaean eon.
This cycle likely came to an end with the rise of cyanobacteria, which produced enough oxygen to overwhelm the methane-producing microbes and end the era of hydrocarbon hazes. Still, if you’re looking for a fresh spin on the post-apocalyptic story, how about finding a way to restart this cycle of thick, impenetrable methane smog? Of course, as an LA resident, that just sounds like Tuesday, but I bet others would find it terrifying.
Nature Geoscience via ScienceNOW.
