Venus may have once been habitable

[Jokodo]

There is a recent study that claims Venus may have been habitable until "recently", 700 million years ago. It's long been known that essentially all of Venus's surface is young in astronomical timescales, about that age. The reason appears to be that due to a lack of plate tectonics, pressure in the mantle could build up until magma will eventually break out and flood the world. The idea if this new study seems to be that that might also be when most today's thick atmosphere gassed out, that it could have had a much thinner atmosphere until then: https://www.google.com/amp/s/www.sc...terious-catastrophe-millions-of-years-ago/amp

This got me wondering: wouldn't a lack of plate tectonics impede actual livability even under a favourable temperature regime? Wouldn't it mean that essential elements get locked away in sediments never to resurface? And isn't it also symptomatic if a lack of water? I thought one of the reasons earth does have plate tectonics is exactly that water acts as a lubricant?

On longer timescales, it seems more plausible, as in this article from a few years back:

https://www.nasa.gov/feature/goddar...deling-suggests-venus-may-have-been-habitable

"Venus may have had a shallow liquid-water ocean and habitable surface temperatures for up to 2 billion years of its early history, according to computer modeling of the planet’s ancient climate by scientists at NASA’s Goddard Institute for Space Studies (GISS) in New York.

...

Way and his GISS colleagues simulated conditions of a hypothetical early Venus with an atmosphere similar to Earth’s, a day as long as Venus’ current day, and a shallow ocean consistent with early data from the Pioneer spacecraft. The researchers added information about Venus’ topography from radar measurements taken by NASA’s Magellan mission in the 1990s, and filled the lowlands with water, leaving the highlands exposed as Venusian continents. The study also factored in an ancient sun that was up to 30 percent dimmer. Even so, ancient Venus still received about 40 percent more sunlight than Earth does today.

“In the GISS model’s simulation, Venus’ slow spin exposes its dayside to the sun for almost two months at a time,” co-author and fellow GISS scientist Anthony Del Genio said. “This warms the surface and produces rain that creates a thick layer of clouds, which acts like an umbrella to shield the surface from much of the solar heating. The result is mean climate temperatures that are actually a few degrees cooler than Earth’s today.”"

 

[repoman]

If Venus ever had earth like life, could it have survived im the upper atmosphere?

 

[Jokodo]

If Venus ever had earth like life, could it have survived im the upper atmosphere?

I guess, but I'm guessing, that depends on hope it lost its habitability - and how fast.

One problem I see for exclusively airborne life more generally is trace elements. There are layers in venusian atmosphere with comfortable temperature and pressure and sufficient water and carbon, but at least on earth, al live additionally requires phosphorus and other elements.

 

[DBT]

If, as it appears, Venus was habitable for something like 2 billion years, what could have caused it to tip from habitable into its current hellish condition...and that it happened relatively quickly in geological terms? I mean, 2 billion years of equilibrium is a long time.

 

[bilby]

If, as it appears, Venus was habitable for something like 2 billion years, what could have caused it to tip from habitable into its current hellish condition...and that it happened relatively quickly in geological terms? I mean, 2 billion years of equilibrium is a long time.

It sounds from the OP as though it dried up. Lack of water leads to a cessation of tectonic plate drift, which in turn leads to an un-relieved build up of pressure in the mantle, ultimately producing a catastrophic planet-wide volcanic episode.

Earth has more water, and is further from the sun, so it's less prone to this issue. I am wondering (as a complete ignoramus about Venusian formation) whether her slow rotation and lack of water might both be caused by the Earth capturing the lion's share of the water and angular momentum imported from the outer solar system during the late heavy bombardment. Perhaps someone who knows about this subject can tell me if I am crazy.

 

[Jokodo]

If, as it appears, Venus was habitable for something like 2 billion years, what could have caused it to tip from habitable into its current hellish condition...and that it happened relatively quickly in geological terms? I mean, 2 billion years of equilibrium is a long time.

It sounds from the OP as though it dried up. Lack of water leads to a cessation of tectonic plate drift, which in turn leads to an un-relieved build up of pressure in the mantle, ultimately producing a catastrophic planet-wide volcanic episode.

Earth has more water, and is further from the sun, so it's less prone to this issue. I am wondering (as a complete ignoramus about Venusian formation) whether her slow rotation and lack of water might both be caused by the Earth capturing the lion's share of the water and angular momentum imported from the outer solar system during the late heavy bombardment. Perhaps someone who knows about this subject can tell me if I am crazy.

My think a more or less earth-like rotation period is the norm rather than the exception - rather than Earth having gained momentum, Venus (and Mercury) have lost it due to tidal effects, being as they are much closer to the sun (and in the case of Venus, potentially amplified by its atmosphere which increases tidal friction).

 

[Speakpigeon]

If, as it appears, Venus was habitable for something like 2 billion years, what could have caused it to tip from habitable into its current hellish condition...and that it happened relatively quickly in geological terms? I mean, 2 billion years of equilibrium is a long time.

We were there. We caused the global warming there. A few lucky survivors escaped to planet bis, the Earth.

And now we're back to square one with no spare planet to escape to.

The CIA is hiding the obvious truth, as always.
EB

 

[T.G.G. Moogly]

As I understand it, there was a significant "resurfacing event" in which tremendous amounts of carbon were volcanically released into the atmosphere, much like our decca traps. This interrupted the carbon cycle and enough carbon could not reenter through the surface fast enough to prevent the extreme warming. The surface of Venus is relatively young, 700 million years.

 

[Fentoine Lum]

If, as it appears, Venus was habitable for something like 2 billion years, what could have caused it to tip from habitable into its current hellish condition...and that it happened relatively quickly in geological terms? I mean, 2 billion years of equilibrium is a long time.

Oh hey, just stick around, watch what we do to this planet.

 

[skepticalbip]

If, as it appears, Venus was habitable for something like 2 billion years, what could have caused it to tip from habitable into its current hellish condition...and that it happened relatively quickly in geological terms? I mean, 2 billion years of equilibrium is a long time.

It sounds from the OP as though it dried up. Lack of water leads to a cessation of tectonic plate drift, which in turn leads to an un-relieved build up of pressure in the mantle, ultimately producing a catastrophic planet-wide volcanic episode.

Earth has more water, and is further from the sun, so it's less prone to this issue. I am wondering (as a complete ignoramus about Venusian formation) whether her slow rotation and lack of water might both be caused by the Earth capturing the lion's share of the water and angular momentum imported from the outer solar system during the late heavy bombardment. Perhaps someone who knows about this subject can tell me if I am crazy.

My think a more or less earth-like rotation period is the norm rather than the exception - rather than Earth having gained momentum, Venus (and Mercury) have lost it due to tidal effects, being as they are much closer to the sun (and in the case of Venus, potentially amplified by its atmosphere which increases tidal friction).

What we see as a current norm rotation period does not necessarily tell us anything about what should be expected when the planets first formed. A current model for the formation of our Moon depict the Earth as having a quite slow rotation period until there was a grazing impact with a massive planetoid. This collision threw off a hell of a lot of crustal material that formed the Moon and imparted a lot of angular momentum to the Earth (a fast rotation period of about 5 or 6 hours/revolution). Since then, the tidal drag of the Moon has slowed Earth's rotation and forced the Moon further away. That drag is still slowing the Earth's rotation and forcing the Moon further away by about four centimeters/year.

Mercury and Venus do not have massive moons to slow their rotation by tidal forces. Mercury is close enough to the Sun for tidal forces between it and the Sun to be significant but Venus is too distant for the Sun/Venus tidal force to have much of an effect.