Space Rocks

What space rocks can teach us about the solar system

Asteroids and comets hold clues to Solar System formation, and even the evolution of life itself.


A billion asteroids twirl around the Solar System along with the planets and moons.

These space rocks can measure as much as 330 miles across (Vesta, the largest asteroid), or shorter than a school bus. And scientists are extremely interested in these airless, rocky objects.


But why? They don’t have ancient lake beds, like Mars, or thick atmospheres full of organic molecules, like Saturn’s moon Titan.


They don’t have internal oceans, like Jupiter’s moon Europa, and they certainly don’t carry life, like Earth.

Here are 5 top reasons why scientists study asteroids — and why you should be interested, too.

1. Asteroids are debris leftover from the early solar system.

To understand Solar System formation, we have to study asteroids. The stuff that makes up asteroids hasn’t changed in billions of years, so they offer insight into the state of the Solar System billions of years ago.

NASA/University of Arizona

This is why NASA’s OSIRIS-REx mission just swiped a sample of the asteroid Bennu to deliver to Earth for study in 2023.

2. Asteroids can tell us about planetary formation


Planets came together when a bunch of stuff smashed together billions of years ago — the leftover asteroids and their chemically unaltered material can tell us more details about how this happened.

NASA’s upcoming Psyche mission will study the asteroid also named Psyche, which scientists think is a leftover metallic planetary core.


3. Asteroids may have delivered Earth's water


For decades, scientists debated where our planet’s water could have come from, given its hot, molten beginnings. One theory is that some water was delivered by asteroids and comets.

The Japanese space agency JAXA also sampled an asteroid and found water molecules locked up in grains of the asteroid’s rock.


4. Asteroids might have delivered the ingredients for life


Molecules like amino acids and sugars essential to life have been found on asteroids, making scientists wonder whether asteroids and comets colliding with ancient Earth could have delivered the building blocks of life.

5. Asteroids can threaten Earth


Of the billion known asteroids, a small population — known as Near-Earth Objects — come close to Earth in their orbits.


Scientists keep an eye on the orbits of these asteroids to make sure we are safe from impacts.

Read more space stories here.


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