# If the Earth would break apart, how likely would the large debris stay in orbit?

In the story I'm writing, Earth gets destroyed and the few million humans that survive go to live on another Earth-like planet.

Since the destruction of the planet, the humans do visit their star system every generation as part of their history and as a memorial to visit where their former home world would be. Almost every human knows about what happened and no one wants to forget the mass of lives that were lost.

What destroys Earth is an alien weapon, like a bomb, that is powerful enough to break into the crust and bury itself into the mantle before it detonates. Designed to warp the gravitic and magnetic fields outward, it causes the crust to crack along the tectonic plates, causing the side it impacted to effectively break away, leaving at least one large plate intact but with an exposed mantle and core (looking a lot like the image below)

I don't know if the planet's remains would still be there. I've seen plenty of things, like bits and pieces in fiction and films where planets remain in orbit like:

Copyright: ABC, Marvel, Mutant Enemy, Walt Disney Distributions 2017

I know that there might be a greater chance that the debris might be pulled back into its mass again but there's also the suggestion that the remains would float off into space since there might not be enough gravity to hold it in orbit or the force of the detonation might send things in all directions.

What I want to know is: how likely are the remains to stay in orbit of the Sun for future humans to visit?

• (1) Any kind of effect which breaks apart large piece of the Earth will liberate more than enough energy to melt the entire crust. (2) After the whatever caused those large pieces to fly away, gravitation will very quickly return the remainder of the Earth to a spherical shape. (3) Some pieces will remain in orbit for a very long time; for example, our very beautiful Moon. Commented May 29, 2020 at 8:58
• introducing Newton's first law... don't expect me to recite for you! Commented May 29, 2020 at 12:28
• SevenEves , writ large Commented May 29, 2020 at 14:25
• The crust is just that, a thin layer of cooled rock on top of the mantle. Plates get pushed around as the mantle convects, and squash up against each other, get pulled apart, and occasionally get pulled down into the mantle. They have basically no structural strength on the scale of the forces required to rip a planet apart. Rather than planetary puzzle-pieces left floating around, you can expect something more like an even more violent version of this: youtube.com/watch?v=3JNNKQrfXzk Commented May 29, 2020 at 16:37
• @elemtilas the Bomb would have buried itself to the lower mantle; just about reach probably the outer core. it's designed it large think the size of Eros but thin and but has three layers; an impact shell (almond-shaped) that burns away on crust impact, the inside shell that shaper in shape and is triggered to bury towards heat and the inside shell (sphere-shaped) is protecting the bomb until detonation at it's designed depth and heat-level. Commented May 29, 2020 at 17:22

Yes, it would probably stay close by unless the explosion was very powerful.

The gravitational binding energy of earth is pretty high. Some chunks might acquire enough energy to escape, but the planet in general would still be gravitationally bound, and the chunks would be a moon, a ring, or collide back into the Earth.

If you want something really weird to happen you can have that as well, since your bomb apparently messes with gravity, but generally, the earth has a lot of gravity, and it's a lot easier to crack it apart than send all the parts away.

It takes a lot of energy to change the altitude of an object's orbit (or to tilt the plane of its orbit). So, if the original explosion wasn't powerful enough to send the fragments flying into space immediately, then all the fragments will still be in pretty much the same orbit the Earth was, no matter how much later you return.

That doesn't mean, however, that they will be in the same position along that orbit. Without going into all the details, they will end up spread out like the asteroid belt – each going around the Sun every 365 days, but at very different positions.

Their collective gravitational field (equal to that of the former Earth) plays a role in how that happens, but it will not be enough to cause them to clump back together.

What would happen first is that when the Earth crust and mantle are broken up it would create a little ring around the rest of the planet. You also say that only the crust and mantle are broken up, and this would mean all the other pieces will come crashing down to Earth. This is because Earth's core and mantle are like 70 to 80 percent of Earth's mass so it will probably attract most of the debris. There is a tiny possibility that some of the debris escaped into orbit of the Sun and hits the other planets but this will not happen to most of the Earth as the mantle and core have a strong enough gravity to hold all the rocks that may have been flown out together.