Joe Strout is right below. Thank you Joe, for correcting my error. I had
forgotten the biggest moons: Ganymede, Titan callisto and Io.

The right conclusion is: All planets, moons, asteroids, Kuiper belt objects,
comets (and other Oort cloud objects) orbiting our Sun form by mass a
continuous serie where are no major gaps in relative mass between two
following objects smaller than Earth untill microscopic dust particles.

However There is major gap in mass 43:1 between the smallest terrestial
planet Mars and Pluto. So we should not call Pluto a planet, if we do not
call all Kuiper belt objects planets as they all form another continous
series by mass with no major gaps by mass.

Antti Järvi





"Joe Strout" kirjoitti viestissä
...
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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