Ganymede Enhanced (APOD 2009 September 20)

[neufer]

• ----------------------------------------------
  . As You Like It > Act I, scene III
  ...........................................................
  CELIA: What shall I call thee when thou art a man?
  
  ROSALIND: I'll have no worse a name than Jove's own page;
  . And therefore look you call me Ganymede.
  . But what will you be call'd?
  
  CELIA: Something that hath a reference to my state
  . No longer Celia, but Aliena.
  ----------------------------------------------

http://antwrp.gsfc.nasa.gov/apod/ap001218.html
http://antwrp.gsfc.nasa.gov/apod/ap090106.html
http://antwrp.gsfc.nasa.gov/apod/ap070824.html
http://antwrp.gsfc.nasa.gov/apod/ap070329.html
http://antwrp.gsfc.nasa.gov/apod/ap041209.html
http://antwrp.gsfc.nasa.gov/apod/ap041111.html
http://antwrp.gsfc.nasa.gov/apod/ap011215.html

[orin stepanek]

I take it that the rayed craters are the younger ones. Some of the craters look as though they be bulged upwards; rather than indented. Could this be a possibility?

Planet sized-- 8) Two moons in our solar system are larger than Mercury; Ganymede and Titan. How big does a moon have to be to be called planet sized?

Orin

[neufer]

I take it that the rayed craters are the younger ones.

That sounds about right.

Some of the craters look as though they be bulged upwards; rather than indented. Could this be a possibility?

Certainly not the floor of a crater if that's what you mean. (E.g., our own moon:)

Planet sized-- 8)
Two moons in our solar system are larger than Mercury; Ganymede and Titan.
How big does a moon have to be to be called planet sized?

Actually a planet is more defined by its mass than its volume:

• A planet must have sufficient mass:
  
  1) for self-gravity to overcome rigid body forces such that
  it assumes a hydrostatic equilibrium (nearly round) shape, and
  
  2) that it is able to clear the neighborhood around its orbit.

If it were my decision I would make the cutoff at 10^23 kilograms
such that Ganymede, Titan & Callisto are "planet sized"

Code: Select all

Mass in
10^22 kilograms

33.022   Mercury 	
--------------------
14.82    Ganymede 	
13.45    Titan
10.76    Callisto
..................
8.932    Io
7.348    Moon
4.80     Europa
2.14     Triton 
--------------------
1.67     Eris  

[/b]