The Last Remaining Protoplanet!

Vesta is believed to be the only remaining rocky protoplanet (with a differentiated interior that was once common in the early inner solar system) which likely coalesced to form the rocky terrestrial planets. It is the second-largest object in the main Asteroid Belt (after the dwarf planet Ceres), the brightest asteroid visible from Earth and accounts for around 9% of the mass of the main asteroid belt objects.


Fast Summary Facts About The Proto-Planet Vesta

  • Discovered: March 29th, 1807 by Heinrich Olbers
  • Name Origin: Named after the virgin goddess of home and hearth from Roman mythology
  • Size: Diameter of 525 km (326 miles)
  • Asteroid Rank: 2nd largest in the Asteroid Belt
  • Surface Gravity: Only 0.025g (about 2.5% of Earth’s gravity!)
  • Orbit Perihelion: 2.15 AU
  • Orbit Aphelion: 2.57 AU
  • Orbital Period: 3.63 years
  • Orbital Inclination: 7.14° to the ecliptic
  • Rotational period: 5.34 hours
  • Density: 3.46 g/cm3
  • Surface: Rocky material consistent with the HED meteorites
  • Surface Temperature: Between -188 °C and -3 °C

Learn More Fun Facts About The Asteroid Belt’s Vesta!

  • During the 18th and early 19th century, the search for the ‘missing planet’ between Mars and Jupiter continued. During this time several asteroids were discovered, Vesta being the forth, so a theory became popular (but ultimately incorrect) that these were remnants of a former planet that was blasted apart.
  • Unlike most asteroids, the interior of Vesta is differentiated with a crust of cooled lava, a rocky mantle and an iron-nickel core. The likely reason for this is that Vesta probably formed soon after the birth of the solar system permitting short-lived radioactive material to heat (and melt) the interior. This differentiation means Vesta is classed as a protoplanet rather than as an asteroid and on account of its nearly spherical shape almost a dwarf planet.
  • One of the unique surface features of Vesta is the extensive network of troughs that encircle Vesta's equatorial region. The largest is named Divalia Fossa and is bigger than Earth’s Grand Canyon and was likely formed as a result of a large impact!
  • Vesta is believed to have been involved in a massive collision which resulted in the Rheasilvia crater, which is about 500 km (310 miles) wide – almost as wide as Vesta itself! The Vesta family of asteroids is probably debris from this collision, several of which have fallen to Earth (known as the Howardite, Eucrite and Diogenite meteorite groups) allowing scientist to study pieces of Vesta itself!
  • Another popular surface feature is a group of three adjacent craters collectively known as the "snowman craters" which by chance forms the appearance of a snowman! How fun to see that on this frozen little world!
  • Vesta has one of the widest brightness ranges recorded of any rocky body in our solar system. This is believed to be due to the bright indigenous rocks and dark impact debris from impactors.
  • One spacecraft has visited Vesta, the NASA launched space probe called Dawn which entered orbit around Vesta on July 16th 2011 and after studying the protoplanet for a year began its journey to Ceres where it would enter orbit in March 2015 becoming the first spacecraft to orbit two objects in space.
  • The gravitational pull of Jupiter likely disrupted Vesta and Ceres formation, without which, the two may well have continued to evolve into a full-sized planet.
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