4 Vesta
4 Vesta is a significant asteroid located in the asteroid belt, which lies between the orbits of Mars and Jupiter, approximately 2 to 4 astronomical units from the Sun. With a diameter of 569 kilometers (359 miles), it is the second-largest asteroid in the solar system, surpassed only by 2 Pallas, and is the second most massive body in the asteroid belt after Ceres. Vesta has a complex internal structure, comprising an iron core, mantle, and crust, similar to terrestrial planets like Earth and Mars. This differentiation suggests it underwent significant geological processes, including melting and volcanic activity, resulting in a diverse surface marked by features such as mountains and impact craters, including the prominent Rheasilvia impact basin.
NASA's Dawn mission, which launched in 2007, aimed to explore Vesta and Ceres to uncover insights about their formation and evolution. The spacecraft arrived at Vesta in July 2011 and provided valuable data until September 2012, revealing its unique characteristics and confirming its role as a source of meteorites found on Earth. Vesta's study not only contributes to our understanding of asteroids but also offers clues about the early solar system and the processes that shaped it.
4 Vesta
FIELDS OF STUDY: Observational Astronomy; Cosmology; Sub-planetary Astronomy
ABSTRACT: 4 Vesta is the second-largest asteroid orbiting in the asteroid belt of the solar system. Though rocky, Vesta is unique in that it appears to have evolved more like a terrestrial planet. Vesta was studied at length in 2011 and 2012 as part of NASA’s Dawn mission.
A Massive Asteroid
4 Vesta is an asteroid. An asteroid is an irregularly shaped, rocky space object that orbits the sun. Vesta is found in the asteroid belt, an oval-shaped ring between the orbits of Mars and Jupiter, about 2 to 4 AU (186 to 370 million miles) from the sun.
Scientists believe that planets formed during the early stages of the solar system when space objects accreted, or came together to create single bodies. However, once the gas giant Jupiter formed, it began interfering with this process. Its size and gravitational force prevented a single planet from coming together from space debris in the outer parts of the solar system. Then, its gravity caused these smaller bodies to collide. These events produced the tens of thousands of rocky, orbiting space objects known as asteroids.
As space objects go, most asteroids are quite small. In fact, many of them are less than a kilometer across. However, Vesta is much larger and more massive. It is 569 kilometers (359 miles) in diameter at its widest point. This makes Vesta the second-largest asteroid in the solar system after 2 Pallas. It is also the second most massive body in the asteroid belt after Ceres. Ceres, once thought to be an asteroid, is large enough to be considered a dwarf planet. Dwarf planets, though nearly round, are not the same as regular planets. They are smaller and do not have the gravity to clear their orbits of other space objects.
Vesta’s Characteristics
Vesta’s cold, rocky surface at first appears similar to most asteroids in the asteroid belt. However, extensive study by NASA’s Dawn mission has revealed a unique object that is more like a planet than an asteroid. It is also one of the few large, intact space objects to have survived since the early days of the solar system.
The Dawn mission helped researchers to understand that Vesta most likely formed like the terrestrial planets Earth and Mars. Like them, Vesta has a separate crust, mantle, and iron core. Vesta’s core is large for its size, with a radius of 110 kilometers (approximately 68 miles). However, unlike Earth’s core, Vesta’s core melted early on. This produced basaltic rock, or solidified lava, over the surface.
Volcanic melting and collisions with other space objects resulted in Vesta’s varied surface features. These include mountains, boulders, and steep cliffs as well as deep craters and troughs. One of the most notable surface features of Vesta is the enormous impact basin Rheasilvia near the asteroid’s southern pole. Researchers believe this crater formed from an impact with a large space object about one billion years ago. This collision most likely launched a large number of rock fragments into space. Some of these objects are believed to have made impact with Earth in the form of meteorites. Meteorites are rocky space particles that survive the journey through the Earth’s atmosphere to land on Earth. The chemical makeup of these meteorites point to their origins on Vesta.
NASA Dawn Mission
The Dawn spacecraft launched from Cape Canaveral, Florida, in September 2007. The mission’s goal was to reach and orbit Vesta and Ceres to learn about their makeup, history, and evolution. These space objects are of particular interest because they are the largest relatively intact bodies remaining from the early days of the solar system.
The Dawn spacecraft reached Vesta in July 2011 and orbited around the asteroid until September 2012. Images and data sent back to Earth helped scientists to gain a deeper understanding of its unique nature. The mission revealed Vesta’s planet-like qualities and confirmed it as the origin of many meteorites found on Earth. The Dawn spacecraft reached Ceres’s orbit on March 6, 2015. This marked the first time a spacecraft had entered the orbit of two space bodies.
PRINCIPAL TERMS
- asteroid belt: an oval-shaped ring in which millions of asteroids orbit, located between the orbits of Mars and Jupiter, about 2 to 4 astronomical units (AU; 186 to 370 million miles) from the sun.
- Dawn mission (NASA): NASA-funded mission to study the asteroids Vesta and Ceres to learn more about their composition, history, and evolution. The mission launched in 2007 and reached Vesta in July 2011 and Ceres in March 2015.
- dwarf planet: a celestial body that has enough mass to attain a nearly round shape, lacks the gravity to keep its orbit free of other space objects, orbits the sun, and does not act as a satellite.
- meteorites: small particles that break off comets or asteroids and survive the journey through Earth’s atmosphere to reach the planet’s surface.
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