What was the Hayabusa-2 mission?

• The Hayabusa-2 mission was launched in 2014 when the spacecraft was sent on a six-year voyage to study the asteroid Ryugu. It was launched by the Japan Aerospace Exploration Agency’s (JAXA). 
• The spacecraft arrived at the asteroid in mid-2018 after which it deployed two rovers and a small lander onto the surface. In 2019, the spacecraft fired an impactor into the asteroid’s surface to create an artificial crater with a diametre of a little more than 10 metres, which allowed it to collect the samples.
• In December 2020, Hayabusa-2 delivered a small capsule that contained the rock and dust samples when it was 220,000 km from the Earth’s atmosphere, which safely landed in the South Australian outback.
• Hayabusa-2’s predecessor, the Hayabusa mission, brought back samples from the asteroid Itokawa in 2010.

Why in News?

• Since the capsule landed on Earth, scientists have been studying the material — weighing merely a few grams, but approximately 4.6 billion years old — in order to explore the foundations of the solar system. Their analyses of the samples have helped us explore the origins of life on our planet.
• Recent findings suggest that water and organic materials might have been brought to our planet from the outer edges of the solar system. The scientists made the hypothesis after analysing samples from the asteroid Ryugu.
• While the composition of particles collected from Ryugu closely matches water on Earth, the study notes there were slight differences, leading scientists to hypothesise that our planet’s water might have also originated from places other than asteroids.

What is an asteroid?

• Asteroids are rocky objects that orbit the Sun, much smaller than planets. They are also called minor planets. According to NASA, there are 994,383 known asteroids, the remnants from the formation of the solar system over 4.6 billion years ago.
• Asteroids are divided into three classes. First are those found in the main asteroid belt between Mars and Jupiter, which is estimated to contain somewhere between 1.1-1.9 million asteroids.
• The second group is that of trojans, which are asteroids that share an orbit with a larger planet. NASA reports the presence of Jupiter, Neptune and Mars trojans. In 2011, they reported an Earth trojan as well.
• The third classification is Near-Earth Asteroids (NEA), which have orbits that pass close to the Earth. Those that cross the Earth’s orbit are called Earth-crossers. More than 10,000 such asteroids are known, out of which over 1,400 are classified as potentially hazardous asteroids (PHAs).
• Ryugu is also classified as a PHA and was discovered in 1999 and was given the name by the Minor Planet Center in 2015. It is 300 million kilometres from Earth and it took Hayabusa-2 over 42 months to reach it.

Why do scientists study asteroids?

• Since asteroids are one of the oldest celestial bodies in the Solar System, scientists study them to look for information about the formation and history of planets and the sun.
• Another reason for tracking them is to look for asteroids that could possibly crash into Earth, leading to potentially hazardous consequences.
• NASA’s OSIRIS-REX mission had collected samples from the asteroid Bennu in 2020, which will be brought to Earth in 2023. Scientists are interested in studying asteroids such as Bennu, because it hasn’t undergone drastic changes since its formation over billions of years ago and therefore it contains chemicals and rocks dating back to the birth of the solar system. It is also relatively close to the Earth.