In article ,
"Jarvi" wrote:

4. The moons, asteroids, comets and kuiper belt objects(KBO) are clearly
smaller in size. The smallest planet Mercury is 4,5 times more massive than
biggest of them, our Moon.

Our Moon is not the biggest of these, by mass or by radius. Sorting by
radius:

Name Orbits Dist(km) Rad(km) Mass(kg)
---- ------ -------- ------- --------
Mars Sun 227940 3398 6.42e23
Ganymede Jupiter 1070 2631 1.48e23
Titan Saturn 1222 2575 1.35e23
Mercury Sun 57910 2439 3.30e23
Callisto Jupiter 1883 2400 1.08e23
Io Jupiter 422 1815 8.93e22
Moon Earth 384 1738 7.35e22
Europa Jupiter 671 1569 4.80e22

.....and sorting by mass, we have:

Name Orbits Dist(km) Rad(km) Mass(kg)
---- ------ -------- ------- --------
Mars Sun 227940 3398 6.42e23
Mercury Sun 57910 2439 3.30e23
Ganymede Jupiter 1070 2631 1.48e23
Titan Saturn 1222 2575 1.35e23
Callisto Jupiter 1883 2400 1.08e23
Io Jupiter 422 1815 8.93e22
Moon Earth 384 1738 7.35e22
Europa Jupiter 671 1569 4.80e22

So, not to pick a nit, but our Moon is smaller than Ganymede, Titan,
Callisto, and Io no matter how you look at them.

Also, Mercury is smaller than Ganymede and Titan by radius, and only
about a factor of 2 larger than Ganymede by mass -- about the same as
the difference between Mercury and Mars. So I don't see a clear
distinction between planets and moons here.

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