Phobos and Deimos Once a Single Moon?

blamanj writes "Phobos (fear) and Diemos (panic), the twin moons of Mars have caused astronomers grief for years, as conventional hypotheses about the moons either violate physical laws or have difficulty accounting for their observed orbits. Now a new hypothesis conjectures that they were once a single moon, that broke apart in an ancient catastrophe."

Comments

Re:FUD

[Anonymous Coward]

Metus, Ambiguitas, and Dubium are latin; whereas Phobos and Deimos are Greek... If my math is correct, of course.

Re:Non-Linear Dynamics

[quinkin]

I agree that that is the situation in a classical two body system.

Unfortunately, classical physics cannot calculate a three-body system (it can be approximated quite closely by using iterative two-body calculations and restricted three-body techniques etc.).

The Earth/Moon orbit, is not periodic but is in fact quasi-periodic (so it has an near periodic cycle - or time to return "near" to origin).

I'll leave calculation of the three body integral as a readers exercise (bad physicist joke).

Q.

Re:FUD

[Antisthenes]

They are, and it goes without saying that Greek is the superior tongue. ;-) Uncertainty would be amphisbetesis, "dispute, controversy" (those e's are eta's, by the way, not epsilon's) and doubt would be apistia, "unbelief, distrust".

S.C. Woodhouse, English-Greek Dictionary
Henry George Liddell, Robert Scott, A Greek-English Lexicon

Re:Doubtful

[Alsee]

Good explanation, thanx. That's sort of been itching at me but I never asked/checked why it works in that direction.

an exercise to the reader to work out what retrograde (backward orbiting) moons do

The bulge would lag even more and the moon would spiral in even faster no matter where it is.

I don't happen to be an expert on Triton, but I would therefore conclude that it is a young moon and started with a much larger orbit.

-

Re:Doubtful

[WolfWithoutAClause]

Do you know how hard it is to land in that kind of gravity?

Yes. It's trivial.

It took a lot of careful effort to manuver NEAR/Shoemaker around Eros.

I wasn't born yesterday. That was because the speed of light made it really difficult to remote control the vehicle at that distance. Stick a man onboard and it's really, really easy.

Asteroids formed inside the "frost-line" in the protoplanetary disk.

True, kinda. But so did the Earth. The frost-line doesn't form until the protoplanetary disk gets blown away when the Sun lit up. The Earth lost most of its water because the Earth got very hot due to volcanic activity after forming, not because of its distance from the Sun. A smaller body wouldn't suffer then same fate (although the surface ice sublimes away within the radius of the asteroid belt.)

And, no, the densities do NOT tell you that they're made of ice. Who told you this?

See this (among many, many other places): Deimos and more particularly check out Phobos

(Or are you making this up as you go?) They're densities are low because they are probably fairly porous.

Really? Where did you get porosity from?

It's a not a very dense rock, so driving in an anchor (how would you do that, anyway?)

Explosives, blow a tubular hole and screw in a crampon. You don't need much strength anyway. Deimos is tidally locked, so using a tether out towards L1 or L2 is pretty simple. Alternatively, just using a free floating station at Deimos' general orbital radius works pretty well too.