Is the Asteroid Vesta a Planet?

Since the dethronement of Pluto as a planet by the International Astronomical Union due to the planet being just like the countless other Kuiper Belt fragments seems somewhat disheartening. Must we clamor for another replacement?


By: Vanessa Uy


Ever since the search of planets far beyond Saturn i.e. far beyond what our naked eye can see had started a technological race to build a bigger - and therefore better – astronomical telescope towards the end of the 18th Century. Though it enabled William Herschel to discover the planet Uranus, this technological race allowed the discovery of a yet unknown region of our Solar System that’s much closer to home. A region that lies the orbit between the planet Mars and the planet Jupiter - namely the Asteroid Belt.

On the first night of the 19th Century, Giuseppe Piazzari discovered the largest of the known asteroids. He christened it Ceres after the ancient Roman goddess of agriculture. Later measurements have shown that the asteroid Ceres has a diameter of 440 miles or 710 kilometers with a surface area of 700,000 square miles or 1,810,000 square kilometers. Other asteroids were discovered in quick succession like Pallas – named after on what the Roman’s referred to as Athena – with a diameter of 300 miles or 480 kilometers. Then came Vesta – named after the Roman goddess of hearth fire – with a diameter of 240 miles or 385 kilometers. And then Juno – named after the queen of heaven in Roman mythology – with a diameter of 120 miles or 195 kilometers. Ceres, Pallas, Vesta, and Juno were often referred to as the “Big Four” of the asteroids because they are the only ones with substantial size. This title not only made these asteroids to assume a roughly spherical shape due to the substantial gravity created by their sheer mass concentration, but also those other asteroid bodies are very small in comparison to form a meaningful numerical ratio.

Though only the third largest of the “Big Four” asteroids, Vesta is the only one of them that can be seen on the Earth’s surface via the naked eye. To wonder why ancient “stargazers” who came scores of centuries before – even Renaissance era astronomers - failed to notice and observe the asteroid Vesta is a 250-page doctoral dissertation subject-in-itself. But the not so cut-and-dried scientific data that defines this asteroid only deepens its own mystery.

A number of people who do astronomy for a living have been intrigued by the subsequent scientific data that pertains to the somewhat quirky “geologic” history of the asteroid Vesta. Compared to other asteroids, the way Vesta evolved i.e. the history of how volcanic basalt migrated to Vesta’s surface and cooled is similar to how our planet Earth evolved through the eons. Ben Zellner, an astronomer at Georgia Southern University, is a proponent of the view that the asteroid Vesta should be considered as a planet in light of its geologic history. Zellner says that: “Early on, it (the asteroid Vesta) went through the same kind of history that the Earth and other rocky planets went through.” Zellner and his colleagues even utilized data from the Hubble Space Telescope back in March of 1995 to create a detailed and updated map of the surface of Vesta. Their Hubble data showed a type of basalt that cools below the surface being exposed by recent – geologically speaking – giant meteorite impacts. One such impact, in fact, is believed to have flung pieces of Vesta flying toward Earth. The different types of basalt that they have observed, says Zellner, only serve to confirm their suspicions that Vesta – though now frozen solid – must once have had a structure similar to the planet Earth, replete with a crust, mantle, and a molten liquid core.

Even if Vesta won’t be declared as a new planet, it doesn’t stand to loose brownie points - as one of the most interesting pieces of real estate in our Solar System. Asteroids are perfect spots for setting up laboratories to explore substances that date back to the formation of our Solar System. It is also a very good place to set up space based astronomical observatories, just think how our planet Earth will look when viewed by a 30 power telescope on Vesta’s surface. It also has a potential use as a future mining colony given that we are running out of profitable ores in which to mine our metals, or to provide as springboards for excursions deeper into the remote corners of the Solar System. The immediate future of mankind has always been part and parcel on our willingness to explore and develop the richest found in these asteroids.