Formation of fictional planet

[phrgarek]

Hy! I was wondering could form a fictional rocky planet, with no water on the surface, but with breathable air(atmosphere) for humans? (i'm not asking could be life there just could this hypothetical planet exist?) ... than, there is of course a logical question, from where could oxygen come into atmosphere and other gases in atmosphere, i know there can be many factors and possibilities, i dunno, water evaporates, but not to form a venus-like atmosphere, or a planet that orbits two suns and get too much of heat, i dunno, for example a 'Tatooine' from 'Star wars'.... nevermind, but as i ask, could this planet exist?

 

[3488]

Welcome to SDC.

I am afraid not. The reason why Earth's atmosphere is as it is is due to life, life that photosyntesises CO2 into O2. No life, no O2 (not to be confused with Atomic Oxygen O that is formed inside stars).

If the Earth suddenly lost all photosynthesising lifeforms, the O2 in out atmosphere would reduce very quickly comparitively over a geological time scale, as it would react with rocks & some would disscociate to form O under solar UV, some would form Ozone O3, which in turn would break down over a relatively short period.

So no, such a planet could not exist.

Andrew Brown.

 

[phrgarek]

ok, thanks, but im still a little bit confused....hmm, i have so many to ask, why if why that, bla bla, but, 'in short way', explain me than this please, because i cannot find the detailed answer nowhere.... Planet Venus, new studies say that once had oceans, rivers, just like earth.... and if we say that this was so, tell me, in period, while water evaporated from Venus surface to create a hellish atmosphere, which create with time such hot envivorment, but just before Venus starts to be so hot, could then exists conditions on Venus, when Venus had no oceans, just desert land, but breathable athmosphere, or, the air was toxic just while oceans start to evaporate, i'm interested in that, so please tell me or explain me that, 'cause, i ask myself and i thought about that so long, but i couldn't ask noone who could explain me that detailed..... ??
thnx

 

[3488]

Well, Venus MAY have had hot water oceans very early on.

Assuming the orbit of Venus has not changed much since formation, Venus recieves approximately twice the amount of solar insolance than Earth does.

The infant Sun was approx 70% as powerful as now, so even in youth, Venus was getting 40% more solar insolance than Earth does NOW.

Evaporation of ealry cytherean oceans did not cause the hellish conditions of today. It was the brightening sun & volcanoes that has caused it.

The vast majority of the ancient H2O on Venus has since dissociated, i.e has been broken down into the constituent Hydrogen & Oxygen atoms due to the solar UV.

Also Venus is thought to resurface itself once every 500 million years or so in fresh lava in planet wide lava flooding events, so there would be no ancient surface exposed today. Venus lacks plate tectonics, so internal heat 'bottles up' then is released in massive volcanism that resurfaces the planet.

Venus certainly, or at least almost certainly periodic hot spot volcanism, the Cytherean equivalent of Yellowstone, Hawaii & The Galapagos Islands. Venis has many shield volcanoes in mainly nine clusters, also suggestive of hot spot volcanism. There is no evidence of rifting volcanoes or subduction zones, so at present appears to be hot spot volcanism. However the hot spot vocalnies known are not enough on their own to release the entire biuld up of internal heat, hense the periodic mass lava floodings.

There is some H2O in the clouds of Venus, some speculation of there even being life in those clouds, though I think with experience on Earth, life needs more than just a few clouds, Earth does not have specific cloud dwelling organisms.

Andrew Brown.

 

[kg]

....The vast majority of the ancient H2O on Venus has since dissociated, i.e has been broken down into the constituent Hydrogen & Oxygen atoms due to the solar UV. ...
Andrew Brown.

I guess free oxygen doesn't stick around for very long but is there any way this process could produce O2 faster than it was removed from an atmosphere? How about a planet with alot of water, an atmosphere of helium (or maybe neon?) around a hot star??