Why does the smaller terrestrial worlds have cooler interiors than the larger ones?

Answer 1

I hope the answer will shock you as much as it shocked me when I crunched the numbers.

You're not going to believe this:

-- Mars is larger than Mercury and has more mass, but has less surface gravity

-- Uranus is larger than Venus and has has more mass, but has less surface gravity.

-- Saturn and Uranus are both larger than Earth and have more mass, but both have less surface gravity.

-- Saturn is larger than Neptune and has more mass, but has less surface gravity.

-- Uranus is larger than Neptune, but has less surface gravity.

Yes. It did take a lot of number crunching.

Answer 2

The Solar System formed from a spinning disc of gas, dust and ice surrounding the young Sun (the solar nebula.) Close to the Sun, rings of dust orbited much faster than those further out. Therefore, closer to the Sun, rings of dust were spinning around very quickly and rubbed against each other, creating very high temperatures. Further out, things were moving much more slowly, and everything was far cooler.

At high temperatures close to the Sun the only solid grains of dust that survived were rocky and metallic, and clumped together to form small, rocky and metallic planets. These planets had weak gravity and could not hold onto the light gases in the solar nebula.

Further out, where things were cooler, water and other hydrogen compounds could freeze, forming solid icy dust. This meant that there was much more solid material to form planets out of, so solid clumps of rock, metal AND ice grew, much bigger than the inner planets. These solid objects grew so big, they began to pull in the lighter gases in the solar nebula, and grew into enormous balls of gas and liquid, with small solid centres (still larger than the inner planets!) This is why small, rocky planets orbit close to the Sun, while large, gassy planets orbit farther out.

This is, of course, according to our current theory of planet formation, and may not be right. The biggest challenge we've faced is to explain the fact that gas giants have been found orbiting very close to their parent stars in other solar systems (known as "hot Jupiters.") Hot Jupiters are the easiest kind of planet to find (the bigger a planet is and the closer it is to its star, the easier it is to detect) - so we've found a lot, but we believe they're comparatively rare. It's thought that Hot Jupiters somehow migrated from the outer parts of their systems to the inner parts - perhaps friction with gases in their nebulas slowed the forming planets down, making them lose energy and fall in closer to their star. Until we find more planetary systems, and find easier ways of detecting planets other than hot Jupiters, we won't know how typical our own solar system is - so stay tuned!

Answer 3

Most common reason is that the smaller body does not have as strong of a gravitational force which causes the moon to be stuck in orbit around it.

Answer 4

It may be that the pressure exerted on its mass by gravity in larger planets has the effect of causing greater friction resulting in greater heat.

Answer 5

I'm guessing because it takes shorter time to cool a smaller thing. It would probably take a longer time to cool down a large planet because there is more to cool down. Understand?

Answer 6

as they are smallar in mass their gases get vapourised fast when compared to larger bodies.

Answer 7

They are smaller the large obviously so it its heat get vaporized

Answer 8

pluto