Vesta: Goddess of the hearth

Vesta, the second largest object in the asteroid belt, is one of the most scientifically important asteroids providing insights about our solar system. Vesta was discovered by Heinrich Wilhelm Olbers on March 29, 1807, in Bremen, Germany. It is a protoplanet, which formed about 4.56 billion years ago, just a few million years after the birth of the solar system. It is located in the main belt at a distance of 2.36 AU from the Sun and has a rotation period of 5.34 hours and an orbital period of 3.63 Earth years. Unlike Ceres, Vesta is not nearly spherical; it is somewhat oblate, possibly due to some past impacts with other bodies. But it is still well differentiated and large—about 530 km—to be called a protoplanet. When Vesta was still forming, Jupiter had already formed, and its strong gravitational force disrupted the other asteroids of the main belt, causing collisions with Vesta and inhibiting its growth into a planet. But while it was growing, it formed a metallic iron-nickel core, an olivine-rich mantle, and a basaltic crust, which makes it a unique asteroid with an internal structure like our terrestrial planets. Vesta weighs approximately 2.6 × 10²⁰ kg, which is about 9% of the total mass of the asteroid belt.

In 1997, the Hubble telescope captured the image of the Rheasilvia impact basin, which is believed to be the source of HED meteorites. A massive impact on Vesta created this basin, ejecting about 1 percent of Vesta into space as other small bodies of the Vesta family and HED meteorites. Some of these meteorites have reached Earth. This was confirmed during analysis, where the composition and spectrum of these meteorites and Vesta matched perfectly. Vesta’s surface is rich in basaltic rocks and pyroxene, confirmed by both spectroscopic analysis from Earth and during the Dawn mission’s survey of Vesta from 2011 to 2012. The Dawn mission further confirmed that Vesta is the parent body of HED meteorites, where both Vesta and the samples we have on Earth share similar geological features. Even before the Dawn mission, the composition of Vesta’s crust was analyzed. The Dawn mission revealed past geological activity on Vesta by observing craters, large troughs, and ridges on its surface. It also found traces of lava flow on its surface, confirming the existence of volcanic activity. Unlike Ceres, there is no known evidence of hydrated minerals on Vesta’s surface, suggesting that Vesta likely had little or no water content. All these features are similar to most rocky planets in the solar system. It also has no atmosphere or evidence of current geological activity, but its structured and layered interior is strong evidence for planetary formation since it formed a few million years after the birth of our solar system.

Even though Vesta is mostly considered a dry asteroid with no known hydrated minerals, in 2017 NASA announced that Vesta has organic-rich compounds near the Cranach crater, which most likely settled on Vesta during the impact of some carbonaceous asteroid, considering Vesta’s oxidizing and anhydrous environment. Vesta provides better understanding about planetary formation and how some planetesimals evolved into planets while others did not, giving insights into how the region of formation affects a planetesimal’s composition and evolution.