Age of planets

Factual Questions
1

I was wondering, would each individual planet (counting Pluto, for the purposes of this GQ) have it’s own specific creation date? Which are the ‘oldest/youngest’ planets? Or were they all created at approximately the same date? I’ve looked on google, but my search terms must have been poor.

Thanks in advance for answers.

2

Don’t know about “specific,” but yes, planets weren’t “created” at the same time, methinks. I believe also that our Moon is older than Earth? Anywho. =D

Cheers!
BA

3

Depends on what you mean by “oldest” – and that’s not mere semantics.

The planets of the solar system formed at pretty close to the same time*, according to the standard theories of planetary formation. So in terms of blunt years in existence, they’re very close to identical.

But “age” also may mean two other things. In the sense of existence of the crust, Blackacre is right – the Lunar surface is, in general, older than the Earth’s surface, in general. And it’s fairly easy to identify specific instances where the reverse is true, but we’re talking average age, not extremes.

And in the sense of “how far along the time span from molten crust to utter heat-death-like rundown of the planetary heat engine is the planet?”, Mars, smaller and colder than Earth, is substantially “older,” even though they were created (in the sense of formed) at the same time.

  • Evidence seems to indicate that the Jovians began to coalesce first, and of course we know nothing of surface conditions on any of them to suggest when they finally took their present form. So have fun with trying to get a better answer than “approximately the same time” in geologic terms.
4

But the moon is actually younger than the planets. The solar system is thought to be about 4.6 billion years old. This is based on the ages of meteorites, as none of the rocks on Earth are that old. But that’s because plate tectonics and weathering keeps recycling and breaking down rocks.

However, the moon has neither plate tectonics nor weathering, so many of its rocks should date to its beginning. However, it turns out that the oldest ones we have are around 100 million years younger than the above figure.

5

Gee, thanks! You are carefully disproving what I specifically said I was not saying.

Please note that the average age of the crust of a given planetary body was the question at hand in that particular paragraph, and I explained just what you said in “disproving” me – that the typical portion of terrestrial crust was substantially younger than the typical portion of Lunar crust, despite their approximate identity in age as planetary bodies.

The “age of the solar system” is relevant to one of the other age issues, but not to that one. You are comparing an apple tree to the Orange Blossom Special in bringing them in.

6

In all fairness, though, you didn’t outright dispute BA’s assumption that the Moon, as a whole, was older than the Earth. It was sorta implied, kinda, but the point needed to be made, IMHO.