Did you spend Asteroid Day this year (June 30) wondering about the formation of the asteroid belt? Or watching "Armageddon," wondering how realistic the scenes were of space rocks bouncing around on an asteroid surface? Even if you didn't, asteroids are difficult to avoid in the news. On June 27, the Japanese space agency JAXA reported that its probe arrived safely at asteroid 162173 Ryugu in the asteroid belt. JAXA plans to land the Hayabusa2 asteroid explorer, gather samples and return to Earth in December 2020.
So, apart from suspenseful script writing and potential doomsday scenarios, why is there so much interest in these space discoveries?
Where Is the Asteroid Belt?
The asteroid belt formed in the early days of our solar system and lies between the orbits of Mars and Jupiter. It's home to billions or possibly trillions of objects, some the size of boulders, others thousands of feet across or larger. Space.com describes them as mostly loose, irregular aggregations of rubble; only larger asteroids like Ceres, which is also classified as a dwarf planet, are close to being spherical.
What Caused the Formation of the Asteroid Belt?
According to Space.com, astronomers think asteroids are left over from the beginning of the solar system. Remnants of the protoplanetary disc of dust and rocks circling the sun after planetary formation gathered between Mars and Jupiter. Collisions brought some together and destroyed others, scattering the debris. Jupiter's massive gravity pull stopped larger planets from forming.
Supporting proof for this comes from other space discoveries; a dust belt circling young star Zeta Leporis as its new solar system develops suggests this is how our own asteroid belt formed, said Space.com.
Another theory proposes that asteroids are the result of planetary destruction, according to Space.com. NASA disagrees, pointing out that the combined weight of asteroids in the belt is much less than our own moon — not enough to form a whole planet.
A new theory suggests the asteroid belt's formation happened because of planets dumping debris into an empty gap. Phys.org reports that radial segregation of asteroid type points to them coming from the nearby planets. Researchers ran simulations to investigate their claim. They showed that the asteroid belt could indeed be a construction dump site, full of leftover planetary building materials.
Why Visit Space Rocks?
Without proof, it's difficult to support a theory. Hayabusa2 could help bring back materials and data to explore. The spacecraft will circle Ryugu, scanning the asteroid's surface with sensors to record surface temperature and mineral distribution. Hovering at medium altitude allows closer visualization, as shown in images from the expedition's Twitter feed.
A planned touchdown on Ryugu's surface this year then deploys surface landers and rovers to map, excavate and harvest samples from the asteroid. Hayabusa2 will blast off with the samples in December 2019 for the return trip back to Earth.
Asteroid Dust Holds the Secrets of the Solar System
Studying the composition of Ryugu samples could tell us not only how asteroids formed but also give clues as to how our solar system began. Composition similar to other planets, for example, could support the theory that planet debris formed the asteroid belt.
This research could also help resource development; asteroids are loaded with minerals and metals useful to us here on Earth. Currently, Asterank, a scientific and economic database of more than 600,000 asteroids, values Ryugu at $82.76 billion USD, with profits projected at around $30 billion. Confirming exact composition from samples would give a more exact valuation and help identify asteroids worth mining.
Rich in metals like platinum and palladium, asteroid mining could be the "gold rush" of the future.
