ASTEROIDS AND COMETS – HOW THEY FORMED, THEIR COMPOSITION AND SIGNIFICANCE

Asteroids and comets are rocky and icy remains of formation of our solar system formed around 4.6 billion years ago. The ice and dust particles came together due to gravity and slowly grew in size.

Asteroids are rocky or metallic bodies that are found in the inner solar system within the asteroid belt between Mars and Jupiter. They have shorter and more circular orbits. During their formation, their growth was continuously disrupted by the immense gravitational pull of Jupiter so they could never become full planets.

Comets originate from the outer, colder region of the solar system beyond Neptune. They are found in the kuiper belt and oort cloud. They are composed of ice, rocks and dust. They develop glowing tails of gas and dust near the sun due to vaporization of ice by solar heat. Their orbits are highly elliptical.

The size of asteroids and comets can vary from small dust particles to hundreds of kilometers in diameter.

EXPLORATION OF ASTEROIDS AND COMETS

Asteroids which are nearer to Earth can be imaged with Earth based radar. Spacecrafts have been sent to few asteroids, such as NASA’s Galileo to Gaspra and Ida and another probe on Eros. Hayabusa spacecraft of Japan became the first to successfully bring back samples from an asteroid. These samples revealed presence of water on an asteroid. Dawn spacecraft of NASA explored Vesta, one of the largest asteroids of solar system. Dawn revealed high amount of water bearing minerals on vesta’s surface. NASA’s mission Lucy is currently on a tour of eight different asteroids.

NASA’s ICE spacecraft in 1985 was the first to fly past a comet. European space agency’s Rosetta mission in 2004 orbited a comet and dropped a lander over it. NASA’s Stardust in 2006 took samples from a comet for the first time which found organic compounds including amino acids.

SIGNIFICANCE OF ASTEROIDS AND COMETS

• Comets and asteroids are most primitive objects of the solar system. They contain record of the physical and chemical processes that occurred during the early stages of evolution of solar system.
• They enable us to understand early planetary evolution.
• Asteroids and comets are rich in organic molecules, amino acids and water. Therefore, it is widely believed that these delivered a significant portion of water on Earth’s oceans. They are also believed to have seeded chemicals necessary for life on Earth.
• An asteroid impact 66 million years ago led to the extinction of dinosaurs on Earth.
• Asteroids are rich in rare metals, iron and water. These may be mined for minerals in future.

Impact by asteroids and comets are capable of ending life as well as flourishing it. Scientists are discovering asteroids and comets with unusual orbits that can pose hazard to Earth. NASA’s Near Earth Object Program was established in 1998 to detect potentially hazardous asteroids and comets that could approach the Earth.

METEOROIDS – Small fragmented debris from asteroids or comets.

METEORS – The streak of light produced when a meteoroid burns up in Earth’s atmosphere.

METEORITES – A meteoroid that survives the atmosphere and hits the ground.