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Is it possible to create an Earthlike planet, that is smaller than the Earth , like for example the size of Mars, by altering the core composition like for example making it:

  • Iron (Piron ): 75.6%
  • Nickel (Pnickel ): 22.0%
  • Other Heavy Materials (Pother ): 2.4%

Is it possible to have a planet with a gravity similar (but not equal) to Earth's gravity, with a similar atmosphere and biosphere as well?

My idea is to have a desert world, so if there are features that make that more likely, that's even better.

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    $\begingroup$ Isn't this what you posted before worldbuilding.stackexchange.com/q/254082/30492 as a closed question? You should edit that post and have it reopened, not repost it. $\endgroup$
    – L.Dutch ♦
    Commented Feb 3 at 21:54
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    $\begingroup$ Does this answer your question? Smaller planet Gravity and similarity to Earth one $\endgroup$
    – Escaped dental patient.
    Commented Feb 4 at 3:56
  • $\begingroup$ How DO I open it ? Sorry but I thoguth now one wanted to answer so I thought to open a new one mostly concerning manipulation of core density. $\endgroup$
    – Naima
    Commented Feb 4 at 9:01
  • $\begingroup$ The moment you say desert world, the same biosphere as earth is impossible. $\endgroup$
    – Zautech
    Commented Mar 8 at 20:38
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    $\begingroup$ @Naima - the answer to the previous question was pretty comprehensive. What wasn't covered? $\endgroup$
    – jdunlop
    Commented Mar 19 at 1:46

1 Answer 1

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The equation for surface gravity is $F=\frac{G\times M1 \times M2}{D^2}$ (The gravitation constant G multiplied by the mass of object 1 multiplied by the mass of object 2. That is then divided by the square of the distance from the center of mass of object 1 to the center of mass of object 2).

You asked,

Is it possible to have a planet with a gravity similar (but not equal) to Earth's gravity, with a similar atmospherr and biosphere as well?

Yes.

Since you guys want to be picky about it, if the smaller world had an extremely dense mass that was not at the geometric center of that world, and if that smaller world had a much less dense mountain geometrically opposite to that mass. Add a moon for adjusting the atmosphere. As long as it satisfied the equation, then that would work. It might have some extreme variation of surface gravity and surface conditions, but in at least part of it the conditions could match those of Earth. It might make for an interesting game world.

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    $\begingroup$ This is not true. You can have a tiny planet with Earth's gravity but only a fraction of Earth's mass. Surface gravity is a function of radius as well as mass. $\endgroup$
    – jdunlop
    Commented Mar 18 at 21:54
  • $\begingroup$ @jdunlop, I missed that. f=gm1m2/r2. OK. I adjusted my answer for that. $\endgroup$
    – Line Item
    Commented Mar 21 at 1:16
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    $\begingroup$ Surface gravity isn't typically expressed as a force, but as an acceleration, since that holds constant for all objects on the surface of a body. I also edited the answer to use mathjax so the formula is legible. $\endgroup$
    – jdunlop
    Commented Mar 21 at 8:45
  • $\begingroup$ @jdunlop, thank you for the edit. I expect it to give you points. But your equation is wrong. It is not GxM. It is GxM1xM2. The gravitation constant G multiplied by the mass of object 1 multiplied by the mass of object 2. That is then divided by the square of the distance from the center of mass of object 1 to the center of mass of object 2. Since you guys want to be picky about it, if the smaller world had an extremely dense mass that was not at the geometric center of that world, and if that smaller world had a much less dense mountain geometrically opposite to that mass $\endgroup$
    – Line Item
    Commented Mar 31 at 1:55
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    $\begingroup$ Sorry, yes. Should've changed the f to a. Will do. $\endgroup$
    – jdunlop
    Commented Mar 31 at 9:35

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