Massive, but small planets

[NavajoEverclear]

well this might not have much application in real life, except adding credibility to a science fiction concept, but i was wondering----- would it be possible that if a small planet, say half the size of earth had a core (not the whole thing so dense so life couldn't develop(well i guess that doesn't matter a ton, but it would make the possibility more interesting)) of a certain mass dense enough that it could have gravity equal to earth (but the planet itself being significantly smaller). Or would such great masses (actually that would still be a lot less than something like a black whole) crunch down the matter around it to equal density, or something? What could possibly produce such an occurance naturally? What impact would this have on life?

----- then how important is gravity to the fromation of life (pretty important i know, but i wonder what the limits are), say a creature on a planet with a significantly greater gravity came to earth, it would probably have strength superior to anything here (having adapted in harsher condition), or does difference in gravity effect pressure enough that the creature would explode in our atmosphere, as we would implode (isn't that what would happen) in theirs?

 

Please answer the earlier questions first, though i'd like them all answered i know its a lot, and so my latter questions i can conclude myself with a basis of knowledge from the first ones.

[alt_f13]

Implosion/Explosion is caused by pressure from all sides. High gravity would crush us. Low gravity would allow us to jump far.

[NavajoEverclear]

so lower pressure within an atmosphere, we would still be able to live? ANYWAY though that wasn't my most important question darnit. No hard feelings though.

[Sayonara]

High gravity would result in a race of Captain Dylan Hunts.

[NavajoEverclear]

I dont know who that is, i looked him up on google, evidently something do with a tv episode or something, probably a dumb one (i dont know i've never seen it).

 

So could that occur, a planet with a dense core, but total only half size of earth(for example), to be of the same gravity? Or would it at least be possible and be able to sustain life? And if it could occur naturally, how would it have happened? Just wondering cuz it would be interesting to think about. Or would the increased density have some other effect that would not allow life to survive?

 

If there is no problem with this , could somehow, we in space create artificial gravity by severely compressing matter---- come to think of it that sounds dangerous, plus where'd you get all the matter from? So forget that last question. (requesting so may doom it to be the only question answered).

[YT2095]

We have a mostly Iron core here on Earth, but a planet with a Lead core would certain have the effect you mention and still be perfectly possible. the inhabitants would be alot shorter than us I would imagine though.

[Janus]

First off, It would be extremely difficult to naturally get a world 1/2 the size of Earth with the same surface gravity.

 

For this to happen the world would have to have an average density 2 times that of the Earth's (5520 kg/m³).

 

We have an iron core now and iron has a density of 7874 kg/m³, about 42% greater than Earth average. (at the core this density increases due to pressure)

 

The planet would have to have a average density of about 11040 kg/m³

 

This is only slighty less than that of Lead at 11340 kg/m³, So unless you have a planet that is mostly core, lead won't do it.

 

Mercury, at 13456 kg/m³ is about 22% percent denser than the needed average density, so you would still need a somewhat larger core.

 

Tungsten has a density if 19300 kg/m³, 75% more than the average density needed, which means you could get away with a somewhat smaller core.

 

Osmium, at 22610 kg/m³ is a little over twice the needed density, so you could get away with even a smaller core.

 

The problem is that one is unlikely to find these heavy metals in high enough concentrations to produce the cores of planets.

 

 

Also, having an heavy metal core would lead to the fact of the planet being rich in heavy metals in its crust. Heavy metals tend to be toxic, which would most likely prevent life from forming.

 

Another thing to consider:

 

While the surface gravity would be the same, the Escape velocity wouldn't.

 

The volume of the planet would be 1/8 of Earth's, and even with 2 times the density, its mass would be 1/4. its radius would be 1/2, so using the formula for escape velocity:

 

v=sqrt(2GM/r)

 

It turns out that the escape velocity would be about only 70% that of Earth's.

 

This, in turn, effects how well the planet can hold on to its atmosphere. So, all other things being equal, it should also have a thinner atmosphere.

[aman]

Would the core matter if there was an aggregate surface of balanced Earthlike elements? I imagine intelligent life may not arise but life should be able to evolve. Twin planets might share a deeper atmosphere if they were close together, maybe?

Just aman