Could this hypothetical xoplanet support life?

KTevolved

Sorry about bringing this up again but something confuses me. I get that the water vapor would only last several billion years but what about the liquid ocean on the surface? The planet would get about 92% solar luminousity the earth does and the reason its heated is the greenhouse gases.
The atmosphere is 1.5 bar which would make the boiling point higher. Plus the atmosphere is denser than earths so wouldnt the oceans stay until its star becomes a red giant or will the oceans dissapear before then? Im just confused how liquid water on the surface can seep, but i fully understand water seeping in the exosphere.

willstaruss22

Yes your star will reach red giant stage well before all the surface water on your planet seeps into space on its own.

KTevolved

How long will the red giant take to evaporate all the surface water? Could life survive after that?

Czcibor

As long as you have liquid water some amount of it would evaporate.

Out of that water that evaporated, some, in upper layers of atmosphere would either be directly lost, or got smashed by UV and some of the hydrogen atoms will be lost. The process would keep an equilibrium by repeating itself. In long run the share of harder to loose deuterium would increase in relation to normal hydrogen.

Actually if the planet was colder with loosing water you might reach an intermediate solution - partially stripped atmosphere -> poor heat transfer -> remaining water mostly frozen in glaciers at the pools.



You have a planet that at the start of your scenario is already at the hotter verge of HZ, right? And it's going to become hotter?

When the conditions are finally right to tip the point the process should be rather fast from geological perspective.

If you include extermofiles that live a few kilometers below the ground I'd give them a chance. As long as the atmosphere is quickly stripped without reaching serious sterilizing everything greenhouse phase, the system might allow some remnants of simple life in some cold oasis.

EDIT:
One factor that I think was missed:

High temperature quickens weathering of silicate materials and helps capturing carbon dioxide.

http://en.wikipedia.org/wiki/Future_...Climate_impact

KTevolved

Yes its in the warmer part of the habitable zone. The temperature over the last hundreds of millions of years have ranged from 285-312 K. Right now its in a warm period. So its only water in the upper part of the atmosphere that gets lost and not water from the surface just reaching escape velocity? There are ups and downs in temperature. Its not in a phasew where the temperature will keep rising up rapidly.

Czcibor

Right. But in long run this process would remove water from surface anyway, just in less direct method.

If you want to have a semi-livable planet after oceans evaporation I have an idea for you:

http://www.astro.washington.edu/cour...DRY_PLANET.pdf

Executive summary: poor heat transfer, dry hell near equator, but at pools liquid water possible

JohnRC

Adding a few points that seem to have been overlooked:

(1) The oxygen-rich atmosphere on Earth has been created by living things. An oxygen-rich atmosphere is a high chemical energy atmosphere, far from chemical equilibrium with the planetary surface. It is something that can only arise on a planet as the result of insolation of photosynthesizing organisms. The carbon dioxide/oxygen system is a dynamic system that needs to be constantly replenished. On Earth the turnover time is 5000 years.

(2) Water vapour is not lost from the Earth's atmosphere. Water is lost in very small quantities as the result of photochemical reaction with solar radiation at high levels in the atmosphere to make hydrogen which is lost, and atomic oxygen which is not. The very low temperatures at the tropopause (~8-15 km altitude) and the mesopause (~80-95 km altitude) are particularly effective at trapping water in the lower part of the atmosphere and minimizing the escape to the outer regions where this photochemistry can occur. Meteoric inputs of water, the most common compound in the solar system, are also significant as a balancing factor for water loss, though we have no accurate way of quantifying these.

(3) An oxygen content of at least around 2% is necessary to maintain an ozone layer (also a dynamic phenomenon), and an ozone layer is the only factor that allows life to flourish on the land surface of a planet. The ozone layer is also a dynamic phenomenon, dependant on chemical processes to regenerate it as it is destroyed by the UV radiation it is shielding.

(4) The Earth's hemispheric symmetry is not nearly as marked as has been suggested in previous posts. The climates in North and South of the Earth are affected by 3 main differentiating influences:
a) 50/50 land to water in the North as against 10/90 in the South.
b) shallow sea ice at the north pole as against huge and high ice cap at south pole. This is in association with mostly land with a few high mountains in the immediate sub-Arctic, as opposed to 99% ocean in the sub-Antarctic.
c) perihelion occurs at summer solstice in the South, meaning a shorter summer season in the South than in the North.

5) On any planet with a large amount of ocean, the atmospheric content of carbon dioxide cannot be higher than about 2% because of immediate equilibrium with bicarbonate and dissolved carbon dioxide in the oceans, and ultimate equilibrium with formation and weathering of carbonate minerals in surface layers.