Sun - Increasing in Luminosity

  • #1
I am currently researching how the sun's steady increase in luminosity is affecting the four inner planets. It's a fascinating subject.

I haven't done any of the calculations yet (mostly because I am not that advanced in math yet), but I was watching a show called, "The Universe." On this particular episode, the subject was the death of stars. The scientists were explaining what conditions would be like on Earth nearer to our sun's demise. The description sounded extremely familiar: the conditions resembled those on Venus.

This set my mind to "runaway mode," and I started thinking about the suspicion that Venus was once like Earth. I combine that with the postulation that the sun is 40% brighter than it was at birth.

Is it possible that Venus' runaway greenhouse effect was the result of an increase in solar luminosity? I know that they have already debunked the whole "global warming resultant from increasing solar luminosity," but is it possible that Earth will eventually resemble Venus?
 

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  • #2
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Interesting questions which require speculations, however, well beyond the tolerance of this establishment.
 
  • #3
Oh, sorry. Sometimes, it is difficult to shut my mind down. I'll try harder to filter my content. :smile:
 
  • #4
Simfish
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This set my mind to "runaway mode," and I started thinking about the suspicion that Venus was once like Earth. I combine that with the postulation that the sun is 40% brighter than it was at birth.

Is it possible that Venus' runaway greenhouse effect was the result of an increase in solar luminosity? I know that they have already debunked the whole "global warming resultant from increasing solar luminosity," but is it possible that Earth will eventually resemble Venus?
Yes, Venus' runaway greenhouse effect was probably the result of a solar luminosity increase that boiled away all its hydrogen (Venus used to have lots of water, and when the hydrogen escaped [when the surface temperature is above the boiling point, all the water vapor will be in a position to photochemically dissociate, and then the hydrogen atoms escpae], the oxygen atoms combined with carbon on the surface to form CO2).

Also, without water, carbon dioxide could not dissolve and form limestone (limestone sequesters carbon) [this might just be a biological process irrelevant to Venus though].[1]

And it will happen to earth too, in as little as 1 billion years. Earth's temperature was warmer in the past primarily because its interior was more active in the past.

[1] Or it might not be. See
In the oceans, dissolved carbonate can combine with dissolved calcium to precipitate solid calcium carbonate, CaCO3, mostly as the shells of microscopic organisms. When these organisms die, their shells sink and accumulate on the ocean floor. Over time these carbonate sediments form limestone which is the largest reservoir of carbon in the carbon cycle. The dissolved calcium in the oceans comes from the chemical weathering of calcium-silicate rocks, during which carbonic and other acids in groundwater react with calcium-bearing minerals liberating calcium ions to solution and leaving behind a residue of newly formed aluminium-rich clay minerals and insoluble minerals such as quartz.
Another thing: plate tectonics died early on in the lifetime on Venus. That also may have affected things (I'm not sure about direction though - it helped subduct carbon, but it also released carbon dioxide into the atmosphere through volcanoes). Here's another quote:

The carbonate-silicate geochemical cycle[1][2] is the naturally occurring reversible chemical reaction with summary equation CaSiO3+CO2<=>CaCO3+SiO2.

Equilibrium of the carbonate-silicate reaction is generally shifted in the favor of carbonate formation under near surface temperature and pressure conditions, but shifts to silicate formation at temperatures above 300 °C. Therefore, at the Earth's surface silicates are converted to carbonate sediments, but these sediments are converted back to silicates during the subduction process.[3] This process is far from being a closed loop, in Earth history generally the formation of carbonates significantly outpaces formation of silicates, effectively dissipating primordial carbon dioxide rich atmosphere. The situation is opposite for Venus due to higher temperatures, so Venus now has a high-density carbon dioxide atmosphere.

The carbonate-silicate cycle is suspected as a reason for the ice ages, because it can create negative feedback on the global temperature with a typical time scale of a few million years, which effectively counters water vapor and carbon dioxide short-term positive feedback.
 
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  • #5
Yes, Venus' runaway greenhouse effect was probably the result of a solar luminosity increase that boiled away all its hydrogen (Venus used to have lots of water, and when the hydrogen escaped [when the surface temperature is above the boiling point, all the water vapor will be in a position to photochemically dissociate, and then the hydrogen atoms escpae], the oxygen atoms combined with carbon on the surface to form CO2).

Also, without water, carbon dioxide could not dissolve and form limestone (limestone sequesters carbon) [this might just be a biological process irrelevant to Venus though].[1]

And it will happen to earth too, in as little as 1 billion years. Earth's temperature was warmer in the past primarily because its interior was more active in the past.

[1] Or it might not be. See

Another thing: plate tectonics died early on in the lifetime on Venus. That also may have affected things (I'm not sure about direction though - it helped subduct carbon, but it also released carbon dioxide into the atmosphere through volcanoes). Here's another quote:
Thanks! That is some interesting information.

If Venus does not have tectonics, then what drives the volcanic activity?
 
  • #6
Simfish
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If Venus does not have tectonics, then what drives the volcanic activity?
Well, magma could still find ways to rise up in a way similar to shield volcanoes. Also, without plate tectonics, magma takes longer to "accumulate pressure", so the mantle pressure all gets released in an entire global resurfacing event. This is all debated and we don't have a firm conclusion yet though.

Anyways, from Wiki

=>

Venus shows no evidence of active plate tectonics. There is debatable evidence of active tectonics in the planet's distant past; however, events taking place since then (such as the plausible and generally accepted hypothesis that the Venusian lithosphere has thickened greatly over the course of several hundred million years) has made constraining the course of its geologic record difficult. However, the numerous well-preserved impact craters have been utilized as a dating method to approximately date the Venusian surface (since there are thus far no known samples of Venusian rock to be dated by more reliable methods). Dates derived are dominantly in the range c. 500 to 750 Ma, although ages of up to c. 1.2 Ga have been calculated. This research has led to the fairly well accepted hypothesis that Venus has undergone an essentially complete volcanic resurfacing at least once in its distant past, with the last event taking place approximately within the range of estimated surface ages. While the mechanism of such an impressive thermal event remains a debated issue in Venusian geosciences, some scientists are advocates of processes involving plate motion to some extent.

One explanation for Venus' lack of plate tectonics is that on Venus temperatures are too high for significant water to be present (Kasting 1988)[72]. [73] The Earth's crust is soaked with water, and water plays an important role in the development of shear zones. Plate tectonics requires weak surfaces in the crust along which crustal slices can move, and it may well be that such weakening never took place on Venus because of the absence of water. However, some researchers remain convinced that plate tectonics is or was once active on this planet.
==

Anyways, I know some famous planetary scientists in my department, so I can ask them too.
 
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  • #10
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The book by Jeffrey Kargel "Mars A warmer wetter planet" has a long description of what's expected for earth in the future, climate and evolution of life. And for Mars.
I doubt the part about what will happen to life in the future is very accurate because it's based on the past adaptations to heat. But life would have billions of years to adapt. Maybe animals could evolve refrigeration. We sure have :)
It goes through the red giant phase, when earth might not be swallowed, and to the bitter cold end.
There would be less CO2 in the atmosphere because it gets absorbed when temperatures go up. That would decrease the total amount of life.
Laura
 
  • #11
davenn
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Thanks! That is some interesting information.

If Venus does not have tectonics, then what drives the volcanic activity?
you dont need plate tectonics to produce volcanoes, hotspots are enough :)
think of Hawaii and Yellowstone as 2 major examples

Dave
 
  • #12
Dotini
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I am currently researching how the sun's steady increase in luminosity is affecting the four inner planets. It's a fascinating subject.
Luminosity may be the wrong question. Try looking instead at the sun's increase in magnetism over the last 8000 years - and especially the last 110.

Respectfully submitted,
Dotini
 
  • #13
Simfish
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^sounds like someone who believes in crackpot theories.
 
  • #14
Dotini
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^sounds like someone who believes in crackpot theories.
Nope. I'll leave the crackpot theories to you. I'm a music major with minors in sex, booze and fast cars. I was was just trying to help out the OP who wanted to know about the inner (really more) planets acting up. I've found observatating to be a good first step in learning more. I actually have a telescope. Do you?

I'll let you think about how this might affect your calculations: http://www.sciencedaily.com/releases/2011/03/110331114935.htm

http://www.sciencedaily.com/releases/2009/10/091016112630.htm
 
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