<p>Venus, currently is not in the habitable/Goldilocks zone. However once it had <a href="https://www.nasa.gov/feature/goddard/2016/nasa-climate-modeling-suggests-venus-may-have-been-habitable/" rel="nofollow noreferrer">deep oceans of water, millions of years ago.</a> based on computer modellings of the climate of the ancient Venus by scientists at NASA’s Goddard Institute for Space Studies (GISS).</p>
<p>This was because at that time Venus actually was in the habitable zone. This shift was because Goldilock's zone radius from the central body, depends upon it's thermodynamic temperature, as more heat is more black body radiation. The temperature is lower in ZAM age, or medium, because the helium fused would have sank down to the core, providing gravitational contraction, which would in turn heat it up.</p>
<p>The solar irradiance was low that time, because the temperature was low therefore the black-body radiation emitted that time was comparatively less. Because of this the Venus was actually in the habitable zone, until, the Sun brightened and made the oceans photocatalyze due to UV rays producing electronegative oxygen readily reacting with the carbon (maybe the comet deposits or solar wind?) making it's  CO2 rich atmosphere (96%!).</p>
<p>But, if we somehow manage to deplete the CO2 level, by capturing the 90 bars in carbonates or other techniques, we probably may in fact be able to terraform Venus. Although it is practically possible only for Type II civilisations, theoretically, if we remove the CO2 and replace it with gases with higher albedo, we can cool down Venus. According to the inverse square law, the solar constant for Venus would be approximately 2800 watts per square meter. If somehow we manage to absorb only 50% of that solar energy and reflect the rest 50%, the temperature of Venus would be roughly be comparable to that of Earth with polar ice caps.</p>
<p><a href="https://i.sstatic.net/F7ZPD.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/F7ZPD.jpg" alt="enter image description here" /></a></p>
<p>Image licensed by <a href="https://en.wikipedia.org/wiki/User:Ittiz" rel="nofollow noreferrer">Ittiz</a> under the <a href="https://en.wikipedia.org/wiki/en:Creative_Commons" rel="nofollow noreferrer">Creative Commons</a> <a href="https://creativecommons.org/licenses/by-sa/3.0/deed.en" rel="nofollow noreferrer">Attribution-Share Alike 3.0 Unported</a> license.</p>

CC BY-SA 4.0
2023-09-22T15:32:45.513Z
Great answer! Also where did you find this image?
Shubhankar Dixit
CC BY-SA 4.0
2023-09-22T16:21:58.160Z
It seems to be this one https://commons.wikimedia.org/wiki/File:TerraformedVenus.jpg and it needs to be properly credited.
Pere
CC BY-SA 4.0
2023-09-23T03:37:41.883Z
@ShubhankarDixit Thank you!. I found it in Wikipedia under Creative Common License since it most likely resembles an ocean.
Arjun
CC BY-SA 4.0
2023-09-23T17:56:15.153Z
I think you'll need to cite something to support the claim that we know Venus had oceans; that seems far from certain.
HDE 226868
CC BY-SA 4.0
2023-09-24T06:39:53.783Z
@HDE226868 Sure! Thank you for telling me that!
Arjun
CC BY-SA 4.0
2023-09-26T08:41:21.250Z
I have issue with the second paragraph. As written, I get the impression CO2 was created by the Sun's UV rays breaking the water molecules from Venus' ancient oceans. If so, what source of carbon reacted with the liberated oxygen? My understanding is Venus' CO2 was released by volcanic activity.
Fred
CC BY-SA 4.0
2023-09-28T05:14:15.413Z
@Fred Interesting. oxygen is an electronegative compound reacting to almost all elements,  even carbon. The source of carbon is largely unknown,  According to my understanding I think from asteroid and comet deposits and ejecta, I am not sure about volcanic plume because I think volcanjsm probably started 2.5 million years. thanks!
Arjun
CC BY-SA 4.0
2023-09-28T09:07:08.140Z
The resurfacing of Venus may have resulted from volcanic activity that commenced 2.5 Ma ago, but that does not mean volcanic activity did not exist on Venus prior to that. Venus & Earth are similar in size & density. Volcanic activity on Earth started billions of years ago. Volcanic activity on Venus could have had a similar history. If so, billions of years of volcanoes emitting CO2 could easily have resulted in the atmosphere that Venus has.
Fred
CC BY-SA 4.0
2023-09-22T11:48:46.260Z
2023-09-28T05:16:42.473Z
2023-09-28T05:16:42.473Z
Arjun
<p>What are the inner and outer edges of the Sun's circumstellar habitable zone or Goldilocks zone?</p>
<p>Here is a link to a list of about a dozen estimates made in the last 60 years, some using complex computer modeling.</p>
<p><a href="https://en.wikipedia.org/wiki/Circumstellar_habitable_zone#Solar_System_estimates" rel="noreferrer">https://en.wikipedia.org/wiki/Circumstellar_habitable_zone#Solar_System_estimates</a></p>
<p>Note that many of them disagree a lot with others.</p>
<p>The semi major axis of he orbit of Venus is 0.723 Astronomical Units (AU) from the Sun, and most of the estimates make the inner edge of the habitable zone farther than that from the Sun.</p>
<p>Only the first estimate is for worlds habitable for humans and life forms with similar requirements.  The rest are for liquid water using life forms in general. On Earth there are many environments where humans would swiftly die which have lifeforms  suited to those environments.  So a planet habitable for some forms of liquid water using life is not necessarily habitable for humans.</p>
<p>So some of the estimates which extend the inner or outer edges of the habitable zone more than others do, do so by assuming specific atmospheric compositions which moderate the temperatures.  And there is no requirement for such compositions to be breathable for humans or for humans to survive longer than seconds on the surfaces of worlds with those hypothetical atmospheres.</p>
<p>Anyway, most estimates of the present habitable zone of the Sun put Venus too close to the sun to be habitable.</p>

CC BY-SA 4.0
2023-09-23T04:26:40.423Z
2023-09-23T04:26:40.423Z
M. A. Golding
<p>I know that Venus is closer to the sun than Earth and if an article I read is to be believed, Venus is hotter than Mercury even though the latter is closer to the Sun. The explanation for this odd phenomenon is, per some scientists, <em>runaway greenhouse effect</em> (the CO2 content of Venus' atmosphere is very high).</p>
<p>It's safe to say that Venus would've been cooler without so much CO2 in its atmosphere. Question is would it be as cool as Earth to allow liquid water to exist if only there wasn't so much CO2 in its atmosphere? Is Venus in our sun's habitable/Goldilocks zone?</p>

<the-sun><venus><habitable-zone><water>
Is Venus in our sun's habitable zone?
Hudjefa
# Is Venus in our sun's habitable zone?

(Asked by: username_0 on 2023-09-22)

I know that Venus is closer to the sun than Earth and if an article I read is to be believed, Venus is hotter than Mercury even though the latter is closer to the Sun. The explanation for this odd phenomenon is, per some scientists, *runaway greenhouse effect* (the CO2 content of Venus' atmosphere is very high).

It's safe to say that Venus would've been cooler without so much CO2 in its atmosphere. Question is would it be as cool as Earth to allow liquid water to exist if only there wasn't so much CO2 in its atmosphere? Is Venus in our sun's habitable/Goldilocks zone?

**Tags:** the-sun, venus, habitable-zone, water

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## 2 answers

### Answer by username_1 on 2023-09-22. Score: 3 | Accepted answer

Venus, currently is not in the habitable/Goldilocks zone. However once it had [deep oceans of water, millions of years ago.](https://www.nasa.gov/feature/goddard/2016/nasa-climate-modeling-suggests-venus-may-have-been-habitable/) based on computer modellings of the climate of the ancient Venus by scientists at NASA’s Goddard Institute for Space Studies (GISS).

This was because at that time Venus actually was in the habitable zone. This shift was because Goldilock's zone radius from the central body, depends upon it's thermodynamic temperature, as more heat is more black body radiation. The temperature is lower in ZAM age, or medium, because the helium fused would have sank down to the core, providing gravitational contraction, which would in turn heat it up.

The solar irradiance was low that time, because the temperature was low therefore the black-body radiation emitted that time was comparatively less. Because of this the Venus was actually in the habitable zone, until, the Sun brightened and made the oceans photocatalyze due to UV rays producing electronegative oxygen readily reacting with the carbon (maybe the comet deposits or solar wind?) making it's CO2 rich atmosphere (96%!).

But, if we somehow manage to deplete the CO2 level, by capturing the 90 bars in carbonates or other techniques, we probably may in fact be able to terraform Venus. Although it is practically possible only for Type II civilisations, theoretically, if we remove the CO2 and replace it with gases with higher albedo, we can cool down Venus. According to the inverse square law, the solar constant for Venus would be approximately 2800 watts per square meter. If somehow we manage to absorb only 50% of that solar energy and reflect the rest 50%, the temperature of Venus would be roughly be comparable to that of Earth with polar ice caps.

[![enter image description here](https://i.sstatic.net/F7ZPD.jpg)](https://i.sstatic.net/F7ZPD.jpg)

Image licensed by [Ittiz](https://en.wikipedia.org/wiki/User:Ittiz) under the [Creative Commons](https://en.wikipedia.org/wiki/en:Creative_Commons) [Attribution-Share Alike 3.0 Unported](https://creativecommons.org/licenses/by-sa/3.0/deed.en) license.

> **Comments:**
> **username_2**: Great answer! Also where did you find this image?  
> **username_3**: It seems to be this one https://commons.wikimedia.org/wiki/File:TerraformedVenus.jpg and it needs to be properly credited.  
> **username_1**: @ShubhankarDixit Thank you!. I found it in Wikipedia under Creative Common License since it most likely resembles an ocean.  
> **username_4**: I think you'll need to cite something to support the claim that we know Venus had oceans; that seems far from certain.  
> **username_1**: @HDE226868 Sure! Thank you for telling me that!  
> **username_5**: I have issue with the second paragraph. As written, I get the impression CO2 was created by the Sun's UV rays breaking the water molecules from Venus' ancient oceans. If so, what source of carbon reacted with the liberated oxygen? My understanding is Venus' CO2 was released by volcanic activity.  
> **username_1**: @Fred Interesting. oxygen is an electronegative compound reacting to almost all elements,  even carbon. The source of carbon is largely unknown,  According to my understanding I think from asteroid and comet deposits and ejecta, I am not sure about volcanic plume because I think volcanjsm probably started 2.5 million years. thanks!  
> **username_5**: The resurfacing of Venus may have resulted from volcanic activity that commenced 2.5 Ma ago, but that does not mean volcanic activity did not exist on Venus prior to that. Venus & Earth are similar in size & density. Volcanic activity on Earth started billions of years ago. Volcanic activity on Venus could have had a similar history. If so, billions of years of volcanoes emitting CO2 could easily have resulted in the atmosphere that Venus has.  

---

### Answer by username_6 on 2023-09-23. Score: 6

What are the inner and outer edges of the Sun's circumstellar habitable zone or Goldilocks zone?

Here is a link to a list of about a dozen estimates made in the last 60 years, some using complex computer modeling.

<https://en.wikipedia.org/wiki/Circumstellar_habitable_zone#Solar_System_estimates>

Note that many of them disagree a lot with others.

The semi major axis of he orbit of Venus is 0.723 Astronomical Units (AU) from the Sun, and most of the estimates make the inner edge of the habitable zone farther than that from the Sun.

Only the first estimate is for worlds habitable for humans and life forms with similar requirements. The rest are for liquid water using life forms in general. On Earth there are many environments where humans would swiftly die which have lifeforms suited to those environments. So a planet habitable for some forms of liquid water using life is not necessarily habitable for humans.

So some of the estimates which extend the inner or outer edges of the habitable zone more than others do, do so by assuming specific atmospheric compositions which moderate the temperatures. And there is no requirement for such compositions to be breathable for humans or for humans to survive longer than seconds on the surfaces of worlds with those hypothetical atmospheres.

Anyway, most estimates of the present habitable zone of the Sun put Venus too close to the sun to be habitable.


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