Between Mars and Jupiter lies a belt of asteroids, which are rocky space rocks. More than a million of them orbit the Sun in this main belt. The first asteroid found, Ceres, was discovered on New Year's Day 1801.
The Sun formed about 4.6 billion years ago from a giant spinning cloud of gas and dust. Planets grew from a spinning disk of gas and dust around the young Sun. Clumps smashed into one another and formed larger and larger objects.
The asteroid belt is made of bits and pieces left over from the early solar system. They never came together into a planet. Early on, the gravity of newly formed Jupiter stopped planet-building in the belt. Only small rocky bodies were left there. Jupiter is the largest planet in our solar system. It is more than twice as massive as all the other planets combined.
An asteroid can have large effects. About 65 to 66 million years ago, a large asteroid hit Earth and helped wipe out the dinosaurs. On 26 September 2022 NASA's DART spacecraft hit the asteroid Dimorphos. It measurably shifted the orbit of Dimorphos. This was the first test of asteroid deflection.
Other missions went to asteroids to collect pieces of them. Hayabusa2, a JAXA mission, made an artificial crater on the asteroid Ryugu. It did this so that it could collect a sample of material from beneath the surface.
NASA's OSIRIS-REx launched in September 2016. It collected a sample from the asteroid Bennu in October 2020 and returned it to Earth in September 2023.
Analysis of the samples that NASA's OSIRIS-REx brought back from asteroid Bennu found amino acids and nucleobases. These are key ingredients for life. The rocks that came back from space held some of the ingredients for life.
Words to know
- asteroid: rocky space rock
- deflection: change of path
- nucleobases: life's building blocks
- artificial: made by people
- orbit: path around something
