4Vesta...the bright asteroid
4 Vesta is the second asteroid relative to its mass discovered in the asteroid belt that occupies the distance between Mars and Jupiter. Its diameter is 530 kilometers, and its mass is about 9% of the total mass of asteroids in that belt.
It was discovered by the German astronomer Heinrich Olbers on March 29, 1807, and he gave it this name, which is due to the goddess of the house in Roman mythology, Vesta.
Sky police
In 1596, while determining the elliptical shape of planetary orbits, Johannes Kepler believed that a planet must exist in the gap between Mars and Jupiter. Mathematical calculations performed by Johann Daniel Titius and Johann Elert Bode in 1772 - later known as the Titius-Bode law - seem to support this prediction. In August 1798, a group known as The Celestial Police formed to search for this missing planet. Among these was the German astronomer Heinrich Olbers. Olerbus discovered the second asteroid known as Pallas. In a letter to a fellow astronomer, he put forward the first theory of the asteroid's origin.
Olbers explained that the fragments of such a planet would intersect at the point of explosion, and again in the directly opposite orbit. He observed these two regions at night, and on March 29, 1807, he discovered Vesta, becoming the first person to discover both asteroids. After measuring several observations over several nights, Olbers sent his calculations to mathematician Carl Friedrich Gauss, who amazingly calculated Pallas's orbit in just 10 hours. He also had the honor of naming the new body. So he chose the name Vesta - the goddess of the hearth and sister to the god Ceres.
NASA's Dawn spacecraft obtained this image with its camera on July 17, 2011. It was taken from a distance of about 9,500 miles (15,000 kilometers) from the protoplanet Vesta. Each pixel in the image corresponds to approximately 0.88 miles (1.4 km) (Image: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA)
Physical properties of Vista
When asteroid Vesta approached Earth in 1996, the Hubble Space Telescope mapped its surface and topographic features. This revealed a large crater in Antarctica that was divided into segments within it. The diameter of the crater is 460 km, Vesta itself is only 530 km away. It traverses an average of 13 km into the Earth's crust, and was most likely formed by a collision in the asteroid's early formative stages. The material ejected from this collision resulted in a number of smaller asteroids, orbiting close to the origin, as well as some meteorites that collided with Earth.
Unlike most asteroids, Vesta's interior is as different as the terrestrial planets. The asteroid contains a crust of cooled lava covering the rocky mantle and iron and nickel. This lends credence to the argument for naming Vesta a protoplanet, rather than an asteroid.
The inner core of asteroid Vesta grew rapidly within the first 10 million years after the formation of the solar system. Its basalt crust formed quickly, over a few million years. Volcanic eruptions at the surface originate from the mantle, and last anywhere from 8 to 60 hours. The lava itself flows from a few hundred meters to several kilometres, with thicknesses ranging from 5 to 20 metres. The lava cools quickly, only to be buried again by more lava until the crust is complete.
Asteroid Vesta shows a huge crater on its southern side. This image shows the asteroid as captured by the Hubble Space Telescope (top, left), as a reconstruction based on theoretical calculations (top, right), and as a topological map (bottom). (Image credit: Ben Zellner (Georgia Southern University) / Peter Thomas (Cornell University) / NASA)
Vesta is unique among asteroids in that it has dark and light spots on the surface, very similar to the Moon. Ground-based observations have determined that the asteroid contains areas of basalt, meaning that lava once flowed across its surface. It also has an irregular shape, close to an oblate spherical shape.
Diameter: 329 miles (530 km).
Mass: 5.886 x 10^20 lbs. (2.67 x 10^20 kilograms).
Temperature: 85 to 255 K (-306 to 0°F / -188 to <18°C)
Luminance: 0.4322
Rotation: 5.342 hours
Orbital period: 3.63 years
Eccentricity: 0886
Apogee: 2-57 African
Perigee: 2.15 astronomical units.
Closest point to Earth: 1.14 astronomical units.
Surface, structure and formation
In 1960, a flash of fireball streaking through the sky over Milipili, Australia, announced the arrival of a piece of the asteroid Vesta on Earth. The meteorite is composed almost entirely of pyroxene, a mineral found in lava flows, and carries the same spectral signals as Vesta.
NASA's Dawn spacecraft, which visited the asteroid in 2012, discovered that the rocky body contains a surprising amount of hydrogen on its surface. It also found bright, reflective areas that may have been left over from its creation.
There are several huge mountain towers on Antarctica Vesta. The massive mountain reaches more than 65,000 feet (20 km) tall, making it as tall as Olympus Mons, the largest mountain (and volcano) in the solar system. Mount Olympus rises about 15 miles (24 km) above the surface of Mars.
Liquid water once flowed across the asteroid. Images taken by the Dawn spacecraft revealed jagged grooves and fan-shaped deposits in eight different impact craters. All eight craters are believed to have formed within the last few hundred million years, which is relatively recent in the life of the 4.5 billion-year-old asteroid.
Scully and her team (she is a graduate researcher at UCLA) believed that features created by debris flows, as opposed to rivers or streams of pure water, carved Vesta's canyons. They suggested that meteorites that struck the asteroid helped melt ice beneath the surface, sending liquid water and small rock particles into flows through the crater walls. This activity suggests the presence of ice buried beneath the surface.
Ice could have been responsible for modifying Vesta's surface. In 2017, a study suggested that smooth patches of terrain on the asteroid often contain high concentrations of hydrogen, which is often seen when solar radiation breaks down water molecules.
A map of Vista's lower elevations has revealed rich geology. The steep slopes on the asteroid, combined with its high gravity, pave the way for it to rise from below and reveal other materials. Dawn also detected a variety of minerals, including some bright and dark materials that could be associated with possible buried snow.
Vestal visitors to Earth
In fact, Vesta's unique composition means it is responsible for a whole host of meteorites. HED meteorites – made up of Howardites, Eucrites and Diogenites – tell the story of Vesta's early life. Eucrites are composed of solidified lava, while diogenites come from beneath the surface. Howardites are a mixture of the two, and were formed when a large collision mixed the two parts together.
Vesta has been suspected of being the source of HED meteorites since 1970. The Dawn Mapping Spacecraft's spectrometers have verified this suggestion. The team believes that these meteorites came from an impact basin called Rheasilvia, which is approximately the same size as Vesta itself. It most likely formed from a collision that removed most of the crust of the southern hemisphere, revealing what was inside the asteroid.
"Vesta is likely close to breaking up," said Carol Raymond, Dawn's lead researcher, noting that these strikes left concentrated sets of troughs - rift lines - around Vesta's equator.
Asteroid exploration
In September 2007, NASA launched the Dawn mission, which is unique in that it was the first aircraft to enter orbit around an object in the solar system. Dawn entered orbit around Vesta in July 2011. After studying the asteroid for a year, it departed Vesta and headed for Ceres in March 2015.
NASA's Dawn mission is to study the properties of the early solar system by analyzing two very different asteroids. Ceres is humid, with seasonal polar caps, and a thin atmosphere. The Vista is dry and rocky. By studying the unique spectral signatures in the rocky crust, our knowledge of our planet, as well as Mars and Mercury, will expand.
Given their size, the two are actually considered protoplanets, or minor planets. Jupiter's gravitational pull disrupted its formation. Without the gas giant Jupiter, the two might still evolve into full-sized planets.
“We now know that Vesta is the only intact planetary mass to have survived from the early days of the solar system,” Carol Raymond, deputy principal investigator at NASA's Jet Propulsion Laboratory in Pasadena, California, told reporters in 2012.
Studying Dawn allowed Vesta to create the best map yet of the asteroid. In October 2010, the Hubble Space Telescope imaged Vesta again. The resulting data revealed that the asteroid was tilted about four degrees more than scientists originally thought. These results helped NASA place the spacecraft in a suitable polar orbit around the asteroid.
Source: Space.com