Starship Asterisk*

http://apod.nasa.gov/apod/ap081013.html

I know this photo talks about Phoenix passing through Ice plumes but I noticed in the upper right hand corner there seems to be a lack of fissures and the scene seems to have more craters. I'm wondering if this is probably a land mass. Could it be that if this moon was to thaw out that it would be very Earth-like? I know Enceladus it thought to have liquid oceans; but maybe there are continents as well.

Orin

orin stepanek wrote:http://apod.nasa.gov/apod/ap081013.html

I know this photo talks about Phoenix passing through Ice plumes but I noticed in the upper right hand corner there seems to be a lack of fissures and the scene seems to have more craters. I'm wondering if this is probably a land mass. Could it be that if this moon was to thaw out that it would be very Earth-like? I know Enceladus it thought to have liquid oceans; but maybe there are continents as well.

Orin

(That should be Cassini, not Phoenix.)

I don't see how anything about Enceladus could be considered "Earth-like". It's only 500 km across (Colorado, where I live, is bigger than that!) I doubt there are any lithic masses near the present surface. The moon is very low density- 1.6 compared with 5.5 for Earth- so a good deal of its volume consists of water. Beneath all that water, there's a silicate core, possibly not even differentiated, but low iron in any case. Assuming the moon is anywhere near hydrostatic equilibrium, there's no way a section of the core could extend 100 km or more up through the ice to the surface.

If Enceladus were to thaw, it would simply go from an icy world to an ocean world, with no dry land.

Thanks Chris! I corrected the title! I don't know why I was thinking about Phoenix. Would a body have to be Earth size to be Earth-like? They are finding planets that are larger than Earth around other planets that are being referred to as Earth-like. What would explain the difference in topography where there isn't any cracks and fissures If not some sort of solid surface such as a land mass?
Orin

To answer part of your question, ALL planets beind termed as Earth Like only refers to the belief that they are rocky worlds as opposed to gaseous worlds. I would also likely imagine that the planet needs to be roughly earth massed to support a dynamic atmosphere with a water cycle. When the mass gets too small, atmospheric pressure forces loss to space. If the mass is too large, atmospheric pressure would in turn increase making it less hospitable (to us). I can't think of an explanation as to the cause for a smooth(er) surface in one area.

orin stepanek wrote:Would a body have to be Earth size to be Earth-like?

The only way to answer that would be to start with a definition for "Earth-like". But I think a body as small as Enceladus would probably fail on most counts: iron poor, low ratio of silicates to water, not massive enough to hold a significant atmosphere.

Chris Peterson wrote:

orin stepanek wrote:Would a body have to be Earth size to be Earth-like?

The only way to answer that would be to start with a definition for "Earth-like". But I think a body as small as Enceladus would probably fail on most counts: iron poor, low ratio of silicates to water, not massive enough to hold a significant atmosphere.

I guess as Earth-like; it would have to have the elements needed to support some type of life. Not being large enough to hold an atmosphere seems to negate this; however underwater organisms would seem possible. Thanks for all your input. I like to dream a little and get carried away once in a while!

Orin

Chris Peterson wrote:If Enceladus were to thaw, it would simply go from an icy world to an ocean world, with no dry land.

orin stepanek wrote:I like to dream a little and get carried away once in a while!

Visualize this. A few billion years from now the Sun expands. Venus and Earth are stripped of all water. One by one, the small icy worlds of the Solar System lose their surface features (take your photos before it's too late), turn to ocean worlds, and end up as bare rocky cores (for those that have one) after all the water is vaporized and blown off into space.

So how far out from the Sun will the melt zone extend? How far out from the Sun will the vaporization zone extend? Will the moons of Jupiter escape the heat? Saturn and beyond? Anyone have a time-lapse movie?

apodman wrote:Visualize this. A few billion years from now the Sun expands. Venus and Earth are stripped of all water. One by one, the small icy worlds of the Solar System lose their surface features (take your photos before it's too late), turn to ocean worlds, and end up as bare rocky cores (for those that have one) after all the water is vaporized and blown off into space.

Actually, I don't think most of the outer moons (with the exception of a few very large one; not Enceladus) could exist as ocean worlds. If they don't have enough mass to hold an atmosphere, they aren't going to be able to sustain liquid water. The surface will boil away, and eventually (but a short while in geological terms) they will be dry to the core, all their water lost to space.

Chris Peterson wrote:The surface will boil away ... all their water lost to space.

http://www.space.com/scienceastronomy/a ... 10412.html

New observations of selected regions of our Milky Way Galaxy show that water is more abundant than expected. The new measurements show that water is the third most common molecule in the regions studied, giving researchers useful information about the abundance of elements available when new planetary systems are formed.

apodman wrote:

Chris Peterson wrote:The surface will boil away ... all their water lost to space.

http://www.space.com/scienceastronomy/a ... 10412.html

New observations of selected regions of our Milky Way Galaxy show that water is more abundant than expected. The new measurements show that water is the third most common molecule in the regions studied, giving researchers useful information about the abundance of elements available when new planetary systems are formed.

If that's the case than life may be fairly abundant in the universe. The trick will be to find it.

Orin

orin stepanek wrote:If that's the case than life may be fairly abundant in the universe. The trick will be to find it.

Lack of water has never been an argument against life in the Universe. Water is a simple compound, long known to be abundant. The exploration of our own system, and even of parts of the Earth, suggests that places capable of harboring life may be common. But really, we know so little about other star systems that this remains highly speculative- particularly given our lack of knowledge about the conditions necessary for life to develop in the first place. It is possible that those conditions are much harder to satisfy than simply being able to support life once it exists.

Just from their simplicity (and light weight), I would expect methane, ammonia, and water to be among the most common molecules in the universe, along with molecular hydrogen, nitrogen and oxygen.

I think most of the conditions for life in the universe are there. http://www.lifeinuniverse.org/Conditions-04-02.html Because of distances involved we may never know. There is the chance that we may discover some simple forms of life; or maybe never. I hope I'm still around if and when we do. To think we are alone in the universe is a big ego trip. Once man thought that the Earth was the center of the universe.

Orin