How old is Jupiter's moon Io?

Answer 1

Since the Big Bang is estimated to be about 13.7 billion years ago, Io or any moon or planet or star must be younger than that. The correct answer for the age of Io would be about 4.5 to 4.6 billion years old.

About 200 million years after the Big Bang (or about 13.5 billion years ago), stars began to coalesce, and around the stars were swirls of matter that are believed to later come together to be planets and asteroids and other objects. Early stars are thought to have produced only smaller atoms, beginning with hydrogen and helium. When these stars collapsed or exploded and then formed other stars, larger atoms were formed by nuclear fusion and eventually all the atoms in our Periodic Table were produced. Samples from our earth, moon, and other parts of the solar system contain these larger atoms, so we know that a long time has passed since early stars began to coalesce. Exactly when we can accept that a moon like Io was finally formed into a moon as the matter came together is a matter of debate and study. Also asteroids and other objects that crashed into Io would add to the mass of Io or any moon. The escape of debris, gas, liquid, and portions of the forming moon that broke away from Io's gravity after collisions would take mass away. A moon like Io can always change by future eruptions, collisions, and many other events.

The earth is estimated to be about 4.6 billion years old, and that may be a good estimate for the age of other bodies in our solar system.