What Exactly Are Asteroids? And What Was the NEAR Shoemaker Mission About?
Key Highlights :
Asteroids are small, rocky bodies that orbit the Sun. They are also known as minor planets, and many of them can be found in the main asteroid belt between the orbits of Mars and Jupiter. These asteroids vary in size from 33 feet (10 meters) to several hundred kilometers, and they are believed to be the remains of planetesimals that formed between Mars and Jupiter.
The Near Earth Asteroid Rendezvous (NEAR) mission was a space exploration mission launched in February 1996. The mission was to study the asteroid 433 Eros, which is one of the largest asteroids in the solar system. The spacecraft orbited Eros for almost a year, passing as close as 4 miles (6 km) and as far as 300 miles (500 km) from the surface. During this time, it measured the asteroid's gravity, photographed the asteroid, and mapped and made chemical measurements of the surface.
On February 12, 2001, the NEAR spacecraft made a controlled descent to the surface of Eros, becoming the first spacecraft to land on an asteroid. After a year orbiting the asteroid, the spacecraft spent two weeks collecting and sending back data before the extreme cold destroyed its communication capabilities. The data gathered during the mission has helped us to understand the composition and structure of asteroids, as well as the origin of the solar system.
Credit with another milestone in space exploration: On February 12, 2001, a spacecraft landed on the surface of an asteroid for the first time in history. After a year orbiting the asteroid 433 Eros, the Near Earth Asteroid Rendezvous (NEAR) spacecraft made a controlled descent to the surface. But what exactly are asteroids? And what was the NEAR Shoemaker mission about?
Asteroids are small, rocky bodies that orbit the Sun. In 1772, a mathematician named Johann Titus and an astronomer named Johann Bode discovered a mathematical sequence that explained the distances from the sun of all the known planets — but there seemed to be one missing. Astronomers began to search for this missing planet, and in 1801, an Italian astronomer named Giuseppi Piazzi found a faint body at that distance that he called Ceres. However, Ceres was fainter than Mars or Jupiter, so Piazzi concluded it was much smaller. Astronomers later found other small bodies in this same vicinity. These objects were named asteroids (meaning star-like).
Most asteroids occupy the main asteroid belt between the orbits of Mars and Jupiter, which is anywhere from 2.1 AU (1.95 x 10 miles or 3.15 x 10 kilometers) to 3.2 AU (3.0 x 10 miles or 4.8 x 10 kilometers) from the sun. There are more than 1 million known asteroids. They are irregularly shaped and vary in size from a radius of 33 feet (10 meters) to several hundred kilometers (Vesta is the largest, with a radius of 329 miles or 530 kilometers). By measuring fluctuations in their brightness, we know that many asteroids rotate in periods of three to 30 days.
Scientists classify asteroids by their composition. Asteroids appear to be of two different origins: planetesimals that formed between Mars and Jupiter, and those that were pulled out of the main asteroid belt by Jupiter's immense gravitational force. Occasionally, Jupiter's gravity pulls an asteroid out of the main asteroid belt, sending it into the solar system. These stray asteroids may collide with planets or, in the case of what are called Trojan asteroids, share an orbit with a larger planet. NASA monitors asteroids that cross Earth's orbit to protect Earth from a possible asteroid impact.
The Near Earth Asteroid Rendezvous (NEAR) mission was a space exploration mission launched in February 1996. The mission was to study the asteroid 433 Eros, which is one of the largest asteroids in the solar system. The spacecraft orbited Eros for almost a year, passing as close as 4 miles (6 km) and as far as 300 miles (500 km) from the surface. During this time, it measured the asteroid's gravity, photographed the asteroid, and mapped and made chemical measurements of the surface.
On February 12, 2001, the NEAR spacecraft made a controlled descent to the surface of Eros, becoming the first spacecraft to land on an asteroid. After a year orbiting the asteroid, the spacecraft spent two weeks collecting and sending back data before the extreme cold destroyed its communication capabilities. The data gathered during the mission has helped us to understand the composition and structure of asteroids, as well as the origin of the solar system.
The NEAR Shoemaker mission was a milestone in space exploration, as it was the first spacecraft to land on an asteroid. It provided valuable data about asteroids and the solar system, which has helped us to better understand the universe around us.
