Tuesday, January 22, 2008

Rocky Planet Pie

Here is the inner solar system, with radii normalized and slices cut according to mass. The Sun is obviously not included. The moons of Mars and the asteroids combined would be less than a pixel wide, so they are omitted. The planets go in from Mars as you go clockwise from 12 o'clock; the Moon is between Earth and Venus. One thing I never realized until it was mentioned in seminar last year is that the Earth is just a little bit bigger than all the rest of the inner solar system put together.

All images are from NASA, taken between 1972 and 2008.

edit- ugly white border problem fixed.


ScienceWoman said...

Pretty diagram.

Old Bogus said...

I never realized how fluffy Mars was before!

Sam Wise said...

Nice diagram, but to pick a "nit," your seminar should have defined "bigger" a bit better. Using numbers from Wikipedia (yeah, I know, but it's the handiest source right now...):

Mercury + Venus + Mars total up to about 0.977 Earth masses.

But things tilt the other way if you look at volume. The total volume of Mercury + Venus + Mars = 1.07 times the volume of the Earth.

So, if you totaled up the rest of the inner solar system (neglecting the asteroids and compression effects for simplicity), you'd wind up with something slightly bigger but slightly lighter than the Earth.

As "old bogus" put it, Mars is fluffy -- and it's got yummy white frosting, too!

C W Magee said...

"(neglecting the asteroids and compression effects for simplicity)"

You can't ignore compression. Mass is conserved. volume is not. if you crashed the Moon, Mercury, and Mars into Venus, the resulting planet would have a smaller volume than Earth. The whole reason that Earth is 6% denser than Venus is solely due to gravitational self-compression.

And if you read the big blue title embedded in the figure, it says, "Inner solar system relative mass"

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