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Hoth is an arctic world where the whole planet is covered in ice. There are some other very cold planets like MZB's Darkover but it is not covered in ice.
I know that Lucas probably just stated that an Ice Planet woudl be cool but I am wondering about possible explanations how a planet could be ice covered yet have both life and a life supporting atmosphere?

Hoth was probably a lot more temperate planet in the distant past. It would have had to have liquid oceans and dry land in order for its current flora and fauna to evolve. For whatever reason, it gradually became cooler until the entire planet became locked in a super ice age. Note that Hoth is not made of ice, but rather is a rocky planet covered in ice and snow. The current plants and animals have adapted to the current state of the planet, although life is still sparce.

Lazy Raptor wrote:Hoth was probably a lot more temperate planet in the distant past. It would have had to have liquid oceans and dry land in order for its current flora and fauna to evolve. For whatever reason, it gradually became cooler until the entire planet became locked in a super ice age. Note that Hoth is not made of ice, but rather is a rocky planet covered in ice and snow. The current plants and animals have adapted to the current state of the planet, although life is still sparce.

It is true, there is geologic eveidence that Earth in the Earth had Ice almost to the equator in the Precambrium ice age. I had forgotten about that. Hmm, Hoth could then be close to Earths orbit assuming a Sol like star.

We don't get many good looks at Hoth's primary. Maybe it's an old star that's getting smaller and cooler, like what happened to Coruscant. The fact that Hoth is the sixth planet in the system doesn't really mean much. While most habitable planets tend to be the third or fourth planet the Hoth system's first five planets could be really close. Either that, or something caused Hoth's orbit to take it farther away fromt the star. I doubt this is the case however, because that would have been too drastic a change to adapt to.

Maybe it was a change in the rotational axis of the planet?

Everything I remember indicates that stars get hotter as time goes on.

Then it's either the oribit or axis change theories. Acutally this does make some sense, because it would explain the low density of life forms on the planet. If it was a gradual cooling, most of the world's life would have adapted. However, Hoth only supports a few species. Maybe they're the survivors of the freezing catastrophe that wiped everything else out. They would have been the plants and animals already adapted to extreme cold, probably polar forms that moved South after the disaster.

Tribun wrote:Maybe it was a change in the rotational axis of the planet?

I think a reduction in greenhouse gas is the most likely solution. Could have had a huge amount of organisms reducing the amount of CO2 in the atmosphere.

That asks the question, are there grasers on hoth which those creatures whihc got Luke eat and what do they eat. Are there some sort of arctic moss like plant on the planet?

The tauntauns used as pack animals by the Rebels are indeed herbivores. They feed on moss and lichen that grow in caves. The tauntauns, in turn, are preyed upon by the wampa ice monsters.

Lazy Raptor wrote:The tauntauns used as pack animals by the Rebels are indeed herbivores. They feed on moss and lichen that grow in caves. The tauntauns, in turn, are preyed upon by the wampa ice monsters.

Tauntauns are native then...I always thought they were brought on the planet by the rebels. I guess that they usually burrow into the ground or find cabves at night since the movie indicates that temperature drops alot at night.

I actually did an undergraduate thesis about the snowball earth hypothesis. Here's a summary:

1. When stars are young, they aren't as hot.
2. A planet's orbit varies over tens of thousands of years, varying the amount of solar radiation it receives.
3. At a certain point during severe glaciation of a planet, you can pass an albedo threshold and then the ice of the planet reflects more heat than it absorbs.
4. Ice spreads quickly after this, and total freezing can occur, which shuts down the carbon cycle.

Now in the case of Precambrian earth, this lasted for several million years until volcanic outgassing raised the CO2 levels to the point where the ice could melt. On earth, temperatures were at about -50 Farenheit for the global average.

In the case of Hoth, it could be the planet is simply in the middle of a 10-million year superglaciation, or it could be that if it was a small planet, it had no volcanism and the lichen-tauntaun-wampa ecosystem was enough to maintain a tenuous atmosphere.

Moral of the story? Proximity to a star is not the main factor in planetary temperature.

Everything has to find a cave at night. That's the only place vegetation grows, so the only reason the tauntauns have to cross the plains in the first place is to get from one known cave system to another. The wampas have their own caves, some of which are likely adjacent to tauntaun habitats. They can either hunt this way or ambush them in transit (like what happened to Luke). IIRC the Rebels carved out Echo Base with high power laser tunneling equipment. After they got so deep they ran into a network of native caves and then had trouble with wampas entering the base since.

CaptainChewbacca wrote:<snip>

Excellent hypothesis! That explains everything rather nicely.

I doubt that Hoth could be an usually small or unusually large planet. Gravity is Earth standard after all.

A planet doesn't have to be small to be volcanically dormant does it?

Here is a question, would the atmopshere the precambrium earth ive age have allowed a human to breath?

Kitsune wrote:Here is a question, would the atmopshere the precambrium earth ive age have allowed a human to breath?

No.

Lazy Raptor wrote:

Kitsune wrote:Here is a question, would the atmopshere the precambrium earth ive age have allowed a human to breath?

No.

Thats what I was afraid of, Earths atmosphere was still pretty primitive at that time. Well, maybe the Permian Ice Age, which seem pretty bad, would be a better example.

It was probably a combination of factors. I don't think Hoth's history is directly analogous to Earth's history anywhere. I basically agree with CaptainChewbacca that it's an ice age out of control. The Permian ice age was bad, but it wasn't that bad, so it really isn't a good example.

Under all the glaciers, Hoth is a rocky planet with continents and oceans. This all has to freeze over. Life would have originally evolved in the oceans near the equator, then moved onto land and followed on par with Earth history. That is until whatever disaster transformed Hoth's most recent ice age into the ugly monster it is. All but the hardiest life forms died out, and the only large plant and animal species alive today are those from the polar regions that were already adapted to the cold. Admittedly, the physics of it all isn't my strong point so I'll leave the details of the ice age to people more learned than I. But really there's a lot about Hoth we can infer from its life forms alone. They really say a lot.

It would be inetsring if we have fish like creatures surviving under frozen over oceans, maybe surviving from volcanic vents

The ecology of Hoth

Kitsune wrote:It would be inetsring if we have fish like creatures surviving under frozen over oceans, maybe surviving from volcanic vents

The ecology of Hoth

We have that on earth, in Antarctica. Lakes that havn't seen the sun for 50 million years and are under a kilometer of ice.

As far as the re-readiation of Hoth's polar creatures following hte onset of an ice age, that seems likely. In the "Star Wars Zoological Field Guide" there are several different species of TaunTaun adapted to the ice-age niches, including the glacier Tauntaun and the climbing tauntaun.

And no, you can't breathe precambrian atmospehres.