A habitable Planet...

[Robittybob1]

 

.....

 

There would've been an earlier atmosphere before the impact. And Moon probably is pretty important for development of life, but we can't say for sure, because we don't know any other places with life other than Earth.

How do you know that there was no atmosphere?

[pavelcherepan]

How do you know that there was no atmosphere?

 

There had to be an atmosphere made up from gases captured during accretion and as Ophiolite has mentioned even before the collision with Theia Earth would've been massive enough to hold atmosphere.

 

https://en.wikipedia.org/wiki/Atmosphere_of_Earth#Earliest_atmosphere

[Robittybob1]

 

There had to be an atmosphere made up from gases captured during accretion and as Ophiolite has mentioned even before the collision with Theia Earth would've been massive enough to hold atmosphere.

 

https://en.wikipedia.org/wiki/Atmosphere_of_Earth#Earliest_atmosphere

@Pavelcherepan: Please accept my apology for I had read your words incorrectly I read "would've" as "wouldn't have". Sorry.

 

So what does that reference say?

"The first atmosphere would have consisted of gases in the solar nebula, primarily hydrogen. In addition, there would probably have been simple hydrides such as those now found in the gas giants (Jupiter and Saturn), notably water vapor, methane and ammonia. As the solar nebula dissipated, these gases would have escaped, partly driven off by the solar wind."

Have you ever attempted to calculate how much matter there was in the Earth region of the solar nebula?

If the Earth existed in some form prior to the solar wind how much gas would be in the atmosphere then?

For even the reference you quote alludes to this: "these gases would have escaped, partly driven off by the solar wind".

PS: I suppose it is not fully clear from where they are saying this gas is escaping from, was it the early atmosphere or just to another part of the solar nebula. Or are they meaning out of our solar system altogether? Has that ever been proven to happen, that the solar wind drives gases out into deep space?

 

I thought Ophiolite said in one of the threads that the collision with Theia did not add much extra mass to the Earth.

 

@Pavelcherepan: So you still don't answer how much atmosphere there would've been.

 

[i'm not sure how to cross reference part way through a post so I'll edit this once I find it]

It is referenced in a post by Ptolemy

http://www.scienceforums.net/topic/27298-a-habitable-planet/page-3#entry903520

 

I don't follow your logic here. The proto-Earth had a mass not dissimilar to that of today's Earth. The gain in mass following the collision with Theia was minimal. Had the proto-Earth remained with its mass that would have been entirely sufficient to retain an atmosphere.

Edited February 7, 2016 by Robittybob1

[pavelcherepan]

 

 

For even the reference you quote alludes to this: "these gases would have escaped, partly driven off by the solar wind".

 

Well, it was probably not the best reference that I could use, but you see it says there that in addition to hydrogen and helium, which indeed must have escaped largely, there were some simple hydrides like water, ammonia and methane. Even in the absence of greenhouse effect the temperature on the Earth is not low enough to get all ammonia and methane frozen (-78 and -182^oC freezing points) and Earth's gravity would've been sufficient to retain these gases. So atmosphere will still be there, although it would be very minor compared to the modern one.

Edited February 7, 2016 by pavelcherepan

[Robittybob1]

 

Well, it was probably not the best reference that I could use, but you see it says there that in addition to hydrogen and helium, which indeed must have escaped largely, there were some simple hydrides like water, ammonia and methane. Even in the absence of greenhouse effect the temperature on the Earth is not low enough to get all ammonia and methane frozen (-78 and -182^oC freezing points) and Earth's gravity would've been sufficient to retain these gases. So atmosphere will still be there, although it would be very minor compared to the modern one.

I don't think that is right. Methane and ammonia are heavy gases compared to hydrogen and helium, so they will be held by gravity IMO ( Please: we should look into this and see what others have found. I have heard that methane in the atmosphere is susceptible to being broken down by UV light so once the Sun fires up the methane will disappear. Do you know what it broke down to? Is it just "methane breaks down to carbon dioxide and water." That would need a supply of oxygen.)

Edited February 7, 2016 by Robittybob1

[pavelcherepan]

 

 

Methane and ammonia are heavy gases compared to hydrogen and helium, so they will be held by gravity IMO

 

Yeah, that's just what I said.

 

 

 

I have heard that methane in the atmosphere is susceptible to being broken down by UV light so once the Sun fires up the methane will disappear. Do you know what it broke down to?

 

Methane breaks down to CH_3, which is still too heavy to escape gravity of proto-Earth.

[Robittybob1]

 

Yeah, that's just what I said.

 

 

Methane breaks down to CH_3, which is still too heavy to escape gravity of proto-Earth.

That is frustrating. That's the second time I read "would've" as would not have. So you agree that these gasses (water methane and ammonia) would be held in the primordial atmosphere. So how much of these gases was there?

CH3 what is that? Did you just know it or did you look it up?

CH3 is the methyl group; so are you saying the methane retained by forming more complex molecules?

Edited February 8, 2016 by Robittybob1

[pavelcherepan]

That is frustrating. That's the second time I read "would've" as would not have. So you agree that these gasses (water methane and ammonia) would be held in the primordial atmosphere. So how much of these gases was there?

 

It's hard to say how much of it there as geological evidence from those times is very sporadic. I'd say that probably not a lot, the atmosphere would've been pretty thin, but as I said, I can't prove it.

 

 

CH3 what is that? Did you just know it or did you look it up?

CH3 is the methyl group; so are you saying the methane retained by forming more complex molecules?

 

I did look it up. CH₃ is a free radical and normally would quickly find a partner to pair up with. I'm not sure if it's retained by forming complex molecules, it's you who implied it. CH₃ can potentially react with another CH₃ molecule and form C₂H₆.

[Robittybob1]

Thanks - Chemistry is definitely not my best subject. If it formed C2H6??? Wikipedia says

"While the methyl group is usually part of a larger molecule, it can be found on its own in either of three forms: anion, cation or radical."

That is about all I can cope with on CH3.

But I have never heard that the Earth's methane was converted to methyl groups .... I'll put that on the back burner for a while.

[Ophiolite]

Latest research analysing the moon and earth suggests the impact was head on and earth and the moon formed with theia being equally dispersed into both bodies.

This is not accurate. The details of the Giant Impact hypothesis continue to be actively debated. I am currently reviewing some 100 papers on the subject, most from the last ten years. My initial scan does not confirm your statement. Your statement reflects one viewpoint among others that are at least equally well supported.

 

My view of the paper presented in the OP is the same. This is simply another perspective and another piece of the puzzle. It should not be taken in any way as definitive.

 

What I find interesting is that after the concept was proposed, first by Hartmann and Davis in 1975 and then, in modified form, by Cameron and Ward in 1976, it was then almost entirely ignored until the Hawaii meeting of 1984, at which it emerged as the strong consensus winner among potential hypotheses. Debate on the details has grown over the years rather than diminished: exciting times.

[Airbrush]

What do you think the odds are of a Planet being habitable, and how did you reach that conclusion?

 

Here is another of my pet peeves about planet habitability. An open ended question like this is meaningless and not of interest. What has meaning and interest is odds of a planet habitable [to us] that is nearby. I don't care about habitable planets in other galaxies, do you? I'm not even interested in habitable planets over 1000 light years away. Only those within striking distance within the next few hundred years.

Edited March 11, 2016 by Airbrush