why don't moons have moon of their own?

I've always been puzzled that even 'planet-sized' moons such as Titan
don't have any satellites going round them.

Is there a particular reason?

dave black wrote:
I've always been puzzled that even 'planet-sized' moons such as Titan
don't have any satellites going round them.

Is there a particular reason?

A moon orbiting a moon is going to have a chaotic orbit. It
will be tugged at by the planet and other moons, changing the
orbit constantly. The orbit would become more and more
eccentric until it either crashed or escaped.

Clear Skies

Chuck Taylor
Do you observe the moon? If so, try
http://groups.yahoo.com/group/lunar-observing/

If you enjoy optics, try
http://groups.yahoo.com/group/ATM_Optics_Software/
*********************************************

Chuck Taylor wrote:
dave black wrote:
I've always been puzzled that even 'planet-sized' moons such as Titan
don't have any satellites going round them.

Is there a particular reason?

A moon orbiting a moon is going to have a chaotic orbit. It
will be tugged at by the planet and other moons, changing the
orbit constantly. The orbit would become more and more
eccentric until it either crashed or escaped.

And by virtue of similar facts, no moon shall ever possess a stable
ring system around it either.

dave black wrote:

I've always been puzzled that even 'planet-sized' moons such as Titan
don't have any satellites going round them.

Is there a particular reason?

If there are several moons in the system then it will be virtually
impossible to find any stable orbits that do not suffer from resonance
coupling with the other moons leading to instability.

However, for the case of the Earth-Moon system mass ratio 82.3:1 there
are huge families of periodic orbits available for a small test
particle. They were investigated extensively during the race to put a
man on the moon. Low energy ones that get close to both Earth and Moon
being of particular interest. These orbits are mostly very strange
shaped - the more exotic they are the more marginal their stability.

ISTR there are potentially stable orbits around the L4 L5 points for the
Earth Moon system - much complicated by the influence of the Sun.

Regards,
Martin Brown

While it is true that there are not moons of moons, there are looser
associations between moons, not unlike those in which some minor planets are
associated with Jupiter or Neptune. For example, there is a resonance
between Ganymede, Io, and Europa such that each has twice the month length
of the next in. In each of Ganymede's months the three align with Jupiter
once in the order EJIG and once in the order IJEG. Saturn's moons feature
two overlapping resonances. Dione and Tethys each have a moon with half the
month and dimensions (Enceladus and Mimas respectively) as well as tiny
moons at their leading and trailing Lagrangian points.

"dave black" wrote in message
oups.com...

I've always been puzzled that even 'planet-sized' moons such as Titan
don't have any satellites going round them.

Is there a particular reason?

From the Suns point of view, could everything that is in orbit around it
(including Earth,Luna,etc) be regarded as its(the sun) moons? If so, then
shouldn't we be part of a Lunar system rather than a Solar system? And if
not, isn't time we were? But seriously, could we all be regarded as
moons of the Sun?
Mike


"dave black" wrote in message
oups.com...

I've always been puzzled that even 'planet-sized' moons such as Titan
don't have any satellites going round them.

Is there a particular reason?

Originally Posted by dave black

I've always been puzzled that even 'planet-sized' moons such as Titan
don't have any satellites going round them.

Is there a particular reason?

Natural moons of moons have probably occured briefly but their orbits tend to be unstable due to the infuence of the adjacent planet. However artificial satellites of a moon are possible - I think our moon has [had] them Like Apollo manned-craft and Clementine for example.

Nytecam