The Return to Venus and What It Means for Earth



Venus hides a wealth of information that could help us better understand Earth and exoplanets. NASA’s JPL is designing mission concepts to survive the planet’s extreme temperatures and atmospheric pressure. This image is a composite of data from NASA’s Magellan spacecraft and Pioneer Venus Orbiter.

Credits: NASA/JPL-Caltech

Take a minute and meditate on the hellish surface of Venus with this interactive 3D model.

NASA and Russia work together to explore Venus science objectives.

Check out the steampunk rover concept created with Venus in mind.

Sue Smrekar really wants to go back to Venus. In her office at NASA’s Jet Propulsion Laboratory in Pasadena, California, the planetary scientist displays a 30-year-old image of Venus’ surface taken by the Magellan spacecraft, a reminder of how much time has passed since an American mission orbited the planet. The image reveals a hellish landscape: a young surface with more volcanoes than any other body in the solar system, gigantic rifts, towering mountain belts and temperatures hot enough to melt lead.

Now superheated by greenhouse gases, Venus’ climate was once more similar to Earth’s, with a shallow ocean’s worth of water. It may even have subduction zones like Earth, areas where the planet’s crust sinks back into rock closer to the core of the planet.

“Venus is like the control case for Earth,” said Smrekar. “We believe they started out with the same composition, the same water and carbon dioxide. And they’ve gone down two completely different paths. So why? What are the key forces responsible for the differences?”

Smrekar works with the Venus Exploration Analysis Group (VEXAG), a coalition of scientists and engineers investigating ways to revisit the planet that Magellan mapped so many decades ago. Though their approaches vary, the group agrees that Venus could tell us something vitally important about our planet: what happened to the superheated climate of our planetary twin, and what does it mean for life on Earth?


Venus isn’t the closest planet to the Sun, but it is the hottest in our solar system. Between the intense heat (900 degrees Fahrenheit heat, or 480 degrees Celsius), the corrosive sulfuric clouds and a crushing atmosphere that is 90 times denser than Earth’s, landing a spacecraft there is incredibly challenging. Of the nine Soviet probes that achieved the feat, none lasted longer than 127 minutes.

By studying this mysterious planet, scientists could learn a great deal more about exoplanets, as well as the past, present, and possible future of our own. This video unveils this world and calls on current and future scientists to explore its many features.

Credits: NASA’s Goddard Space Flight Center/David Ladd

From the relative safety of space, an orbiter could use radar and near-infrared spectroscopy to peer beneath the cloud layers, measure landscape changes over time, and determine whether or not the ground moves. It could look for indicators of past water as well as volcanic activity and other forces that may have shaped the planet.

Smrekar, who is working on an orbiter proposal called VERITAS, doesn’t think that Venus has plate tectonics the way Earth does. But she sees possible hints of subduction — what happens when two plates converge and one slides beneath the other. More data would help.

“We know very little about the composition of the surface of Venus,” she said. “We think that there are continents, like on Earth, which could have formed via past subduction. But we don’t have the information to really say that.”    

The answers wouldn’t only deepen our understanding of why Venus and Earth are now so different; they could narrow down the conditions scientists would need in order to find an Earth-like planet elsewhere. 

Hot Air Balloons

Orbiters aren’t the only means of studying Venus from above. JPL engineers Attila Komjathy and Siddharth Krishnamoorthy imagine an armada of hot air balloons that ride the gale-force winds in the upper levels of the Venusian atmosphere, where the temperatures are close to Earth’s.     

“There is no commissioned mission for a balloon at Venus yet, but balloons are a great way to explore Venus because the atmosphere is so thick and the surface is so harsh,” said Krishnamoorthy. “The balloon is like the sweet spot, where you’re close enough to get a lot of important stuff out but you’re also in a much more benign environment where your sensors can actually last long enough to give you something meaningful.”

A team of JPL engineers tests whether a large balloon can measure earthquakes from the air

A team of JPL engineers tests whether a large balloon can measure earthquakes from the air. The team proposes to measure “venusqakes” from the temperate upper atmosphere of Venus, using an armada of balloons.

Credits: NASA/JPL-Caltech

The team would equip the balloons with seismometers sensitive enough to detect quakes on the planet below. On Earth, when the ground shakes, that motion ripples into the atmosphere as waves of infrasound (the opposite of ultrasound). Krishnamoorthy and Komjathy have demonstrated the technique is feasible using silver hot-air balloons, which measured weak signals above areas on Earth with tremors. And that’s not even with the benefit of Venus’s dense atmosphere, where the experiment would likely return even stronger results.

“If the ground moves a little bit, it shakes the air a lot more on Venus than it does on Earth,” Krishnamoorthy explained.

To get that seismic data, though, a balloon mission would need to contend with Venus’ hurricane-force winds. The ideal balloon, as determined by Venus Exploration Analysis Group, could control its movements in at least one direction. Krishnamoorthy and Komjathy’s team hasn’t gotten that far, but they have proposed a middle ground: having the balloons essentially ride the wind around the planet at a steady speed, sending their results back to an orbiter. It’s a start.

Landing Probes

Among the many challenges facing a Venus lander are those Sun-blocking clouds: Without sunlight, solar-power would be severely limited. But the planet is too hot for other power sources to survive. “Temperature-wise, it’s like being in your kitchen oven set to self-cleaning mode,” said JPL engineer Jeff Hall, who has worked on balloon and lander prototypes for Venus. “There really is nowhere else like that surface environment in the solar system.”

By default, a landing mission’s lifespan will be cut short by the spacecraft’s electronics starting to fail after a few hours. Hall says the amount of power required to run a refrigerator capable of protecting a spacecraft would require more batteries than a lander could carry. 

Sue Smrekar, seen here at the 2018 media briefing before the landing of NASA's Mars InSight

Sue Smrekar, seen here at the 2018 media briefing before the landing of NASA’s Mars InSight, is a planetary scientist at NASA’s Jet Propulsion Laboratory. She believes exploring Venus will reveal important details about how rocky planets form and whether other planets are capable of supporting life.

Credits: NASA/JPL-Caltech

“There is no hope of refrigerating a lander to keep it cool,” he added. “All you can do is slow down the rate at which is destroys itself.”

NASA is interested in developing “hot technology” that can survive days, or even weeks, in extreme environments. Although Hall’s Venus lander concept didn’t make it to the next stage of the approval process, it did lead to his current Venus-related work: a heat-resistant drilling and sampling system that could take Venusian soil samples for analysis. Hall works with Honeybee Robotics to develop the next-generation electric motors that power drills in extreme conditions, while JPL engineer Joe Melko designs the pneumatic sampling system.

Together, they work with the prototypes in JPL’s steel-walled Large Venus Test Chamber, which mimics the conditions of the planet right down to an atmosphere that’s a suffocating 100% carbon dioxide. With each successful test, the teams bring humanity one step closer to pushing the boundaries of exploration on this most inhospitable planet.

For more information about Venus, visit:

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Rick K
December 12, 2019 2:52 am

So who “destroyed” Venus’ atmosphere by flying in aircraft to far-off climate conferences and driving cars with internal combustion engines and lordy! Who knew there used to be cows on Venus??

Reply to  Rick K
December 12, 2019 12:13 pm

““Venus is like the control case for Earth,” said Smrekar. “We believe they started out with the same composition, the same water and carbon dioxide. And they’ve gone down two completely different paths. So why? ”

Well just a wild guess would be that Venus is a lot closer to the sun?

One may believe that Venus was in a similar orbit to us, if one reads Immanuel Velikovsky but the “paths” mentioned above need some more scientific research in my view.



Reply to  Roger
December 12, 2019 1:06 pm

Roger – your’s is just a wild guess (“closer to the sun”). Climate Science is real, as it relies on computer models, which are more trustworthy than observation.

Who would believe that being nearer to a heat source might make an object hotter? That only seems obvious to a Boomer, not a Doomer. What do Boomers know?

Reply to  Roger
December 12, 2019 6:36 pm

How close planet is to the sun has very little to do with how hot it is. Solar energy is needed for photosynthesis which is why Earth’s orbit is referred to as the “green zone”. Venus is covered by an umbrella that no light can pass through of sulfur dioxide making the upper atmosphere cold enough to turn carbon dioxide frozen. No heat from the sun can penetrate by the fact of its existence.
If you list the planets from hottest to coldest, it starts with Jupiter (which is so hot it has a atmospheric layer of ionized plasma creating its giant magnetic field)
Then Saturn, Neptune, Uranus (all of which are warmer under their atmosphere than the photosphere surface of the sun). Then Venus, mercury, Earth, (The average temperature of earths moon is 100° colder than earth!) then Mars.
Large solar influence on a planet is determined mostly by it’s atmosphere. (or lack there of) Day and night temperature swings are greatest on Mercury, our moon, Mars then Earth. The rest of the planets are hard to measure because they emit more energy than they receive from the sun.

John Tillman
Reply to  Max
December 14, 2019 1:51 pm

Heat is also probably transfered from the lit to dark side through the lithosphere as well as atmosphere, given such slow rotation:

But, as Mercury shows, the hot, heavy atmosphere also plays a role.

Ron Long
Reply to  Rick K
December 12, 2019 1:11 pm

Rick K, you’re close to getting yourself in trouble. I am sure I read once that women are from Venus, and it looks like you are referring to them as “cows”.

December 12, 2019 2:56 am

Venus’ climate was once more similar to Earth’s, with a shallow ocean’s worth of water.

Yeah, right.

Reply to  fretslider
December 12, 2019 4:07 am

Is there any evidence for this? Seems like a bold assumption to make!

John Tillman
Reply to  Edmundo
December 14, 2019 2:18 pm

No evidence. But NASA and other alarmists have been promoting this scenario, based entirely upon GIGO computer gaming. As noted, the conjecture fails if young Venus spun even a fraction as slowly as its present stately pace of once every 243 Earth days. Here’s the latest version of the modeling:

“A caveat to this scenario is that its primordial rotation rate needs to be slower than a 16-day long Earth sidereal day.”

Alarmists have always spun Venus as a warning about possible runaway warming on Earth. But the alleged threat is just CACA spin.

John Tillman
Reply to  John Tillman
December 14, 2019 2:19 pm

When and if NASA goes there and finds granite, then there’d be some evidence of ancient liquid water on the surface.

Charles Higley
Reply to  fretslider
December 12, 2019 5:10 am

“Now superheated by greenhouse gases, Venus’ climate”

That just plain wrong. It’s gravitational compression that makes Venus’s atmosphere so hot. It also is not a greenhouse in any way as sunlight does not reach the surface and heat it. It has a permanent cloud deck and the clouds absorb the insolation.

Reply to  Charles Higley
December 12, 2019 5:48 am

Yep. Nikolov and Zeller and Conolly and Conolly. No water, either.

Steve Keppel-Jones
Reply to  Charles Higley
December 12, 2019 6:04 am

Glad you pointed that out, Charles. I was going to say “are you sure it’s the greenhouse gases that make the surface hot, and not, for example, the 90-bar atmospheric pressure???”

Mars has an almost entirely CO2-based atmosphere too, but for some reason it’s not quite as hot as the surface of Venus.

And apparently, at the altitude where Venus’s atmosphere is only 1 bar, its temperature is the same as Earth’s would be if we were at the same distance from the Sun.

Robert W Turner
Reply to  Steve Keppel-Jones
December 12, 2019 7:19 am

Mars has a higher partial pressure of CO2 than Earth does. It’s 8X higher iirc.

Reply to  Steve Keppel-Jones
December 12, 2019 8:24 am

Yes, runaway GHG as an explanation for Venus is a red herring and is one of the consequences of misapplying feedback analysis. In no way shape or form is Venus any kind of analog for Earth as the two atmospheres play significantly different roles relative to the planets thermal equilibrium with the Sun.

The role played by the Venusian atmosphere is more like that of Earth’s oceans, both of which have about the same mass. The Venusian solid surface is decoupled from the Sun in the same way that Earth’s solid surface at the bottom of the deep ocean is. Both exhibit a constant temperature with no diurnal or seasonal variability and the temperature of both is dictated by the properties of the matter between it and the surface in DIRECT equilibrium with the Sun.

Earth is basically a water world where the Sun heats the top of the oceans which then heats the atmosphere. On Venus the Sun heats the cloud tops which heat the top of the CO2 ocean whose PVT profile then dictates the surface temperature below. The Venusian clouds are thermodynamically decoupled from the solid surface below, unlike Earth clouds which are tightly coupled to the oceans by the hydro cycle. Absorption and emissions by Earth clouds relative to averages over periods of time longer than the hydro cycle can be considered a proxy for energy absorbed and emitted by the oceans. The fact that this is not true for Venus is why Venus is so different.

John Tillman
Reply to  co2isnotevil
December 12, 2019 9:19 am

Total mass of Earth’s oceans is an estimated 1.35 x 10^18 metric tonnes; that of Venus’ atmosphere “only” 4.8×10^17 tonnes.

Venusian surface pressure is comparable to about 3000 feet deep, but average ocean depth is around 12,000 feet.

Reply to  co2isnotevil
December 12, 2019 5:04 pm

That is really interesting, John. I never knew Venus’s atmosphere was about half the mass of all the Earth’s oceans. That is insane.

John Tillman
Reply to  co2isnotevil
December 12, 2019 6:14 pm

Yup. Trippy.

But then CO2 is heavier than H2O.

When an atmosphere is like an ocean.

Reply to  co2isnotevil
December 12, 2019 7:01 pm

Isn’t the CO2 a supercritical fluid at the surface? In which case it can be properly considered a liquid ocean.

Reply to  co2isnotevil
December 13, 2019 3:26 am

It should be noted that there is no protective magnetic field to prevent atmosphere loss. The astounding amount of CO2 on Venus is due to the rapid loss of hydrogen, as it was stripped off of water molecules. Then oxygen does as oxygen does, and oxydized whatever carbon and sulfur that was available. Four billion years later, this is what you get.

Reply to  co2isnotevil
December 13, 2019 10:20 am


This doesn’t explain why Venus has at least an order of more carbon than Earth. Given that they supposedly formed in the same place, this shouldn’t be the case.

My guess is that it was a small gas giant that wandered too close to the Sun and all the lighter gases were stripped away. One of those lighter gases was water vapor some of which was scavenged by Earth.

Reply to  Steve Keppel-Jones
December 12, 2019 6:17 pm

Actually, a trifle warmer – somewhere between 4 and 6 degrees (Celsius), calculating from NASA data.

However, the 1 bar level is either right below or just inside the bottom edge of the sulfuric cloud layer – more concentrated than any but the nastiest volcanic outflows on Earth. That accounts for at least the majority of the additional temperature.

John Tillman
Reply to  Charles Higley
December 12, 2019 6:18 am

Around ten percent of ToA sunlight reaches the surface, which is still a lot, equivalent in power to about 20% on Earth, as opposed to the actual 65 to 70%. Earth also reflects a lot from its icy and watery surface.

Venus is hot because of its slow rotation rate, aided by an atmosphere which keeps the night side hot as well as the day hemisphere.

Reply to  John Tillman
December 12, 2019 5:45 pm

The combination of a long day and little to no diurnal variability in the Venusian surface temperature is an indication that the Sun has very little direct effect on the Venusian surface temperature. Like Earth oceans, the Venusian atmosphere is the primary repository of its stored energy, a thin sliver of which near the clouds has an effect on the temperature of the virtual surface of Venus in direct thermal equilibrium with the Sun.

On Earth, only a thin layer on top of the oceans has any effect on the temperature of the virtual surface in direct thermal equilibrium with the Sun.

John Tillman
Reply to  co2isnotevil
December 14, 2019 8:58 am

The surface of Venus recieves directly and indirectly about 10% of ToA irradiation, equivalent to ~20% of Earth’s surface insolation. Another ~14% is absorbed in the atmosphere, and 76% reflected away.

But the long day makes a huge difference, plus the low axial tilt and circular orbit. Sunshine, however attenuated, hits the surface for 257 times as long as on Earth. The hotter air also helps slow the loss of absorbed heat, and keeps the night side as blistering as the day side.

So the Sun does indeed cause Venus’ heat. The lit side of also slowly rotating Mercury gets hot as well, but its dark side cools off.

If Mercury turned as slowly as Venus, it would get even hotter than it is and more so than Venus, even with cooling off during its long night. But Mercury rotates 1.68 times more rapidly than Venus.

Farmer Ch E retired
Reply to  Charles Higley
December 12, 2019 7:18 am

If you were to compress earths atmosphere to that of Venus, Earth would become about twice as hot as Venus due to the adiabatic heat of compression (absolute temperature scale). This, of course, would not reflect a steady-state Earth temperature.

Reply to  Farmer Ch E retired
December 12, 2019 7:58 am

Correct. Heat gained by atmospheric compression would eventually be lost to space, and compression would no longer give the continual energy source to keep the atmosphere hot. The energy source has to be continual, and atmospheric compression is not. Only retention efficiency of solar energy can supply that.

John Tillman
Reply to  donb
December 12, 2019 9:40 am

Compression stays the same as long as the mass of the atmosphere remains the same. Adding a fourth CO2 molecule per 10,000 dry air molecules would ever so slightly increase the mass of our air, since CO2 weighs more than major constituents N2 and O2.

gommers jjm
Reply to  donb
December 12, 2019 1:22 pm

The temperature of the surface is defined by the inner heat of the Venus core. the high density of the atmosphere combined with the resistance of radiation to space limits the surface temperature to 480 oC

Reply to  Charles Higley
December 12, 2019 10:15 am

Nope, planets achieve balance between incoming solar radiation and outgoing IR, with minuscule addition of geothermal and nuclear decay heat added.

Convection, evaporation, and clouds, are the mechanisms by which those phenomena form, and end up controlling the surface temperature, whether on Earth, Venus, Titan, etc. The only thing gravity has to do with it is the density of the atmosphere at different altitudes and the temperature change with altitude (lapse rate for meteorologists) due to adiabatic temperature change as parcels of atmosphere convectively ascend or descend doing or receiving expansion or compression work from surrounding parcels.

High gravity, cloud cover, and lack of something resembling “rain” inhibit surface cooling on Venus. The concept of gravity being the cause of the surface temperature is bogus.

Reply to  DMacKenzie
December 12, 2019 5:16 pm

So why is mars, with its 90% CO2 atmosphere, so cold if atmospheric density does not play a role? More atmosphere means more heat capacity, sure, but gravity does play a role in that PV = nRT. Gravity containing an atmosphere makes pressure, 90 bar’s worth on Venus, so temperature T and/or the number of molecules n must rise. There is only so much n can rise, so that leaves T as the only degree of freedom left (as V is mostly fixed too). So P drives T and T drives P. Doesn’t help the entire planet is in a mega hurricane which also makes some heating from friction, though I would doubt it is much. There is one thing we know for certain: thicker the atmosphere hotter the planet at a given distance from the sun, and vice versa.

Reply to  DMacKenzie
December 12, 2019 7:45 pm

My home is in a valley surrounded by snow capped mountains. No snow at my house. What is the difference? Atmospheric pressure. Whenever a low pressure storm passes over, the Mercury/air pressure drops, so does the temperature. Always. The Chinook winds heat up 5.4° for every thousand feet it drops over a mountain range. No solar influence. Only the increase in barometric pressure. The temperature difference between the north pole and the south pole is considerable, one is at sea level, the other one at 10,000 feet with less air pressure.
Mount Everest receives more energy from the sun due to its altitude. Death Valley is below sea level. Which do you think is hotter? The one with more air pressure? No, that’s got to be bogus.

Original Mike M
Reply to  DMacKenzie
December 12, 2019 8:55 pm

I suggest a centrifuge experiment to create an artificial pressure gradient within a thermally insulated chamber. Some say that although a temperature gradient ought to initially develop upon spin-up, temperature will equalize over time. Others say the gradient will develop and persist.

I cannot think of a better way to put this question to rest?

Jim Whelan
Reply to  DMacKenzie
December 13, 2019 9:55 am

If the compression was static you would be right. However the constant input of solar energy warms gases which rise moving the energy from the surface to upper levels. The gases lose their energy and drop back into the denser levels (replacing the rising hot gases and warm adiabatically in the process. As a result you have a steady state of a warmer surface and cooler gases at the higher altitudes. The result is that the radiative cooling occurs, on the average, higher in the atmosphere. The denser the atmosphere, the more significant the temperature differential between the radiative average surface and the actual surface.

David Blenkinsop
Reply to  Jim Whelan
December 15, 2019 1:18 am

Yes, this is how I understand the more-or-less conventional general theory of compression and “greenhouse” effects too. So, it those terms, it is almost undeniable that the “temperature differential” from lots of pressure would naturally tend to make the surface a lot hotter, other things being equal! Even in conventional theory or “Arrhenius-like” theory terms, how then can these NASA people claim that Venus surface was cold ages ago but now is so hot because it is “Now superheated by greenhouse gases”?

I mean, for the surface to have been much cooler in the past, Venus would have to have had much less atmosphere overall (given that the adiabatic mixing and the lapse rate as such shouldn’t vary a lot with the IR activity in the gas mixture).

Paul Penrose
Reply to  Charles Higley
December 12, 2019 10:21 am

Exactly right. But, just for fun, can anybody explain in simple terms why the higher pressure equates to higher temperature? Hint: you have to first define just what “temperature” is a measurement of – and if you say “heat energy” then you get the buzzer and the big red-X across your face.

Reply to  Paul Penrose
December 17, 2019 9:59 am

More gas molcules means more collisions imparting energy to a temperature sensor.

Reply to  fretslider
December 12, 2019 5:46 am

Almost certainly untrue. Gigo.

Robert W Turner
Reply to  fretslider
December 12, 2019 7:18 am

That’s how far I read. I’m not bothering with reading pseudoscience.

Now who is eager to join manned missions with pseudoscience believers designing the missions?

Curious George
Reply to  fretslider
December 12, 2019 11:15 am

Isn’t it a beautiful scientific speculation?

John Tillman
December 12, 2019 3:03 am

The computer model which derived a once habitable Venus assumed a rotation rate no slower than once every 16 Earth days. Venus presently orbits backwards at once every 243 days.

If anything close to this axial spin rate obtained when its surface first cooled over four billion years ago, then Venus never had an ocean. Given Mercury’s also slow rotation, it’s likely that moon-free Venus has always spun slowly.

Mercury’s orbit is highly eccentric, while Venus’ is nearly circular. It also has very little axial tilt, so practically no seasons.

Its atmosphere does help account for surface heat, but not mainly because Venusian air is 96% CO2. Virtually airless Mercury’s night side cools off, but Venus’ doesn’t, because of its dense atmosphere, with high winds. Less than 10% of incident sunlight reaches the surface, and all but three percent of that indirectly, by scattering in the air. Surface pressure (93 bar) is comparable to 3000 feet deep in Earth’s oceans.

John Tillman
December 12, 2019 3:06 am

On Earth, subduction requires water. Would be a surprise if today’s dry Venus has tectonics.

December 12, 2019 3:47 am

Science fiction. Dang, I thought I was on a science site……Maybe I need to up my game and find a REAL science site.

December 12, 2019 4:01 am

Venus may have had a moon in the past. Mercury might have been that moon, but the Sun grabbed it. But Venus has no moon now, and it’s logical to ask if that has anything to do with what has happened since Venus formed.

Maybe the answer is that if Venus had a moon, it wouldn’t be in its current state.

John Tillman
Reply to  Sara
December 12, 2019 5:01 am

Might depend upon how the moon formed. If, as hypothesized for Earth, by impact with a planetesimal, then Venus would probably spin faster, so be cooler.

A large moon might also have kept Venus’ dynamo going, inducing an internal magnetosphere, which would have helped to retain water vapor.

Venus is so hot primarily because it turns 243 times more slowly than Earth. That it does so in the opposite direcction as well doesn’t make much difference.

John Tillman
Reply to  John Tillman
December 12, 2019 5:13 am

Actually 257 times, since Earth is a little bigger than its evil (near) twin.

December 12, 2019 4:14 am

The “hot technology” sounds very useful. Could mean also NASA becomes useful again.

Chris G
December 12, 2019 4:50 am

All five planets with deep atmospheres are commonly described as having a greenhouse effect or internal heat. However this depends on what depth is assumed as the “surface”.

The energy balance of Venus requires only a small additional fix at the top of its atmosphere. The other four worlds with deep atmospheres are also closer to balancing at their tropopauses than at the arbitrary 1 bar usually assumed as the “surface”. Allowing for variations in Bond Albedo or emissivity it could be that all deep atmosphere worlds balance at their tropopauses.

Considering that worlds with no atmosphere must radiate from their surfaces where would you expect worlds between “no atmosphere” and “deep atmosphere” to be? Both Earth and Titan have a temperature balance half way up the atmosphere.

We now have:
Deep atmosphere = balance at tropopause
No atmosphere = balance at surface
moderate atmosphere = balance between surface and tropopause

Consequently it is possible that there is minimal (possibly none at all) greenhouse effect or internal heating on any world, it all depends on the location in the atmosphere you use.

John Tillman
Reply to  Chris G
December 12, 2019 5:19 am

The greenhouse gas hypothesis (arguably an observation, not just an hypothesis) posits (or observes) that the effective emission height in the atmosphere changes with varying GHG concentrations:

Reply to  John Tillman
December 12, 2019 5:27 am

The model that Philip Mulholland built for me shows that one gets a raised surface temperature with no greenhouse gases at all.
Convection creates both the lapse rate slope and the raised surface temperature and, critically, the convective circulation adapts to neutralise any potentially destabilising influence from the radiative characteristics of atmospheric constituents.

John Tillman
Reply to  Stephen Wilde
December 12, 2019 5:37 am

In the case of water vapor at least, the GHE is palpable. It’s why humid nights are warmer than clear ones. Atmospheric H2O of course also makes air locally denser, but not by much, given that it’s lighter than N2 and O2, and at most in a concentration of 40,000 ppm in the moist tropics.

Reply to  John Tillman
December 12, 2019 5:50 am

That is a local effect only which generally requires humidity to be held near the surface by an inversion aloft which usually requires descending (and thus warming) air aloft. As soon as the inversion dissipates you get accelerated convection to neutralise any local surface warming effect from the humidity.
If one takes a planet as a whole there is no need for any radiative gases to be present to produce a surface warming effect once convective overturning is fully in place.
One can never prevent convective overturning above a spherical body lit by a point source of light which is why the concept of an isothermal atmosphere is physically impossible.
The AGW theory relies upon a radiatively transparent atmosphere becoming isothermal but that concept is fatally flawed.
Some have posited an experiment involving a column with vertical sides as proof that an isothermal atmosphere can be achieved but the presence of vertical sides removes the exponential increase in volume with height that leads to the linear lapse rate slope which in turn causes convection, inevitably, to develop.
So that alleged ‘proof’ is fatally flawed.

John Tillman
Reply to  John Tillman
December 12, 2019 6:35 am

I said nothing about “proof”. Science doesn’t do proof. That’s for math. Science does confirmation and falsification.

The moderating effect of atmospheric H2O isn’t just local. It’s observable across the entire planet. It both warms and cools, depending upon whether the main effect is shading, convective and evaporative cooling or retarding cooling.

Robert W Turner
Reply to  John Tillman
December 12, 2019 7:24 am

Water vapor has a relatively high heat capacity and that is why humid nights are warmer than dry nights. Radiative emissions from gases are minuscule and have little to do with temperature.

John Tillman
Reply to  John Tillman
December 12, 2019 7:57 am


Thanks for the link.

But I find experimental laboratory results and field observations to support a GHE from radiative physics. I’d be happy to be disabused of that conclusion, but in any case, the effect of adding a fourth, fifth or sixth CO2 molecule per 10,000 dry air molecules is negligible.

The lab figure of about 1.1 degree C per doubling is probably close to the effect in the complex climate system, since net feedback effects are liable to be slightly positive, or even negative, on a homeostatic water world.

Hence, rather than IPCC’s (and Charney’s 1979 range) band of 1.5 to 4.5 degrees C per doubling, with a central estimate above 3.0, the actual global range is liable to be ~0.6 to 1.6 K.

I emphasize global, since, for instance, no warming has been observed at the South Pole, despite the increase in CO2. And that’s where the GHE should be most evident.

Lewis and Crok’s best ECS estimate was 1.75 degree C, in a range of of about 1.3–2.4°C. Lindzen, the world’s top atmospheric physicist, and Choy (revised) found, based upon evidence from satellite measurements, that ECS is likely to center on 0.7ºC, well below IPCC’s band. I’m with them, ie net negative feedbacks, hence no worries, let alone no climate “emergency”.

Reply to  Chris G
December 12, 2019 5:25 pm

On top of its cloud layer, at the photosphere if you will, Venus has about 330K. That is just about the temperature a perfect black body would have at Venus’ position. Venus receives some 654W/m2, so..

(654/5,67e-8)^0.25 = 327K

The rest is due to the adiabatic lapse rate, which exists totally independent of GHGs. What constitutes the “GHE” on Venus is the cloud layer, not GHGs. And yes, it is quite the same on Earth.

Mark Broderick
December 12, 2019 4:53 am

“Now superheated by greenhouse gases, Venus’ climate was once more similar to Earth’s, with a shallow ocean’s worth of water. ” ?

I stopped reading after that !

December 12, 2019 4:56 am

“Now superheated by greenhouse gases”

I stopped reading after that. Venus’s heat has nothing to do with “greenhouse gases”, but everything with atmospheric density and pressure.

John Tillman
December 12, 2019 4:56 am

Smrekar states as fact what is only the result of a question-begging computer game, ie a model designed to show what its programmers wanted to find.

We’ll have to go there to discover the truth, but it’s unlikely that Venus ever had an ocean. And if it did, it probably wouldn’t have lasted long.

Venus has been the poster child for alarmists like Jim “Venus Express” Hansen, aka “Boiling Oceans”, but its heat owes more to a leisurely spin rate than to a 96% CO2 atmosphere.

Its SO2 clouds reflect about 76% of ToA solar irradiation. This high Bond albedo makes the planet appear very bright. More than another 15% is absorbed in the atmosphere, leaving less than ten percent to reach the surface. So the Venusian atmosphere actually offers shade.

As noted above, however, the thick air keeps the dark side as hot as the lit half of the planet. Here are figures for equatorial rotation speed, day and night side temperatures and surface pressure of the three innermost planets and the Moon:

Datum: Rotation Rate; Day Side T; Night Side T; Surface Pressure

Mercury: 10.892 km/h; 450 °C; -275 °C; ≲ 0.5 nPa
Venus: 6.52 km/h; 462 °C; 462 °C; 9.2 MPa (91 atm)
Earth: 1674.4 km/h; 17 °C*; 11 °C*; 101.325 kPa (1.0 atm)
Moon: 16.655 km/h; 106 °C; -183 °C; Negligible and variable**.

*Assuming 14 °C mean T (possibly too low) and average of 6 °C difference between day and night (WAG). Close enough for nongovernmental work.

**Lucey et al. (2006) give 107 particles cm−3 by day and 105 particles cm−3 by night. With equatorial surface temperatures of 390 K by day and 100 K by night, the ideal gas law yields pressures (rounded to the nearest order of magnitude) of: 10−7 Pa by day (one picobar) and 10−10 Pa by night (one femtobar).

John Tillman
Reply to  John Tillman
December 12, 2019 5:32 am

Here is Way and Del Genio’s 2019 computer exercise, building upon their 2016 game reported here then:

What’s new is that the duo now argue that Venus might have had an ocean all the way up until the 200 to 800 million year-ago resurfacing event (previously estimated at 300 to 500 Ma). They speculate that before this time, Venus’ atmosphere had less CO2, but that volcanism associated with the upheaval released so much GHG that the formerly wet planet lost its water. Previous hypotheses of an ocean imagined that surface water lasted only briefly after Venus’ formation.

Among the problems with their Way and Del Genio’s latest speculation is that we don’t know if the apparent resurfacing was a one-off event, or if it happens periodically, in lieu of terrestrial-style plate tectonics. It might even happen more or less continuously, with areas of the planet erupting at different times, replacing all of the surface on the timescale of hundreds of millions of years, except possibly for two seeming “continental” elevated masses.

If heat, pressure and corrosion-resistant probes do manage to survive long enough at or near the surface to find out, discovery of granite would support the hypothesis of a once watery surface.

December 12, 2019 5:06 am

It is all about atmospheric mass:

Venus simply held on to more mass in its atmosphere than Earth or Mars did.

Robert W Turner
Reply to  Stephen Wilde
December 12, 2019 7:27 am

Or more of Venus’ mass became a part of the volatile fraction in the first place.

On the outer Barcoo
December 12, 2019 5:17 am

Now superheated by greenhouse gases, Venus’ climate …..”. Since the atmosphere on Mars also has a similar carbon dioxide concentration, how come it is so much colder?

Reply to  On the outer Barcoo
December 12, 2019 5:35 am


Low atmospheric mass.
Mars doesn’t have the same CO2 concentration as Venus but it does have a similar proportion of CO2 in the atmosphere.

Reply to  On the outer Barcoo
December 12, 2019 5:51 am

Shhhhh! Heretic!

Ed Zuiderwijk
Reply to  On the outer Barcoo
December 12, 2019 6:07 am

Martian atmosphere is thin, only 1% of the Earth’s. Even at 100% CO2 it is practically transparant, incapable of trapping radiant heat. Venus’ atmosphere is thick, both physically at 100 times Earth’s, and optically, which makes it trapping radiant heat very efficiently.

One could wonder why Earth, apparently, has a Goldilocks atmosphere, not too thin and not too thick, to give a temperature right at the value where water is in all three phases, which, arguably makes life possible. As far as I know not a single climatologist has ever asked that question, probably because they have been too busy with their beloved models.

John Tillman
Reply to  Ed Zuiderwijk
December 12, 2019 7:09 am

Real climatologists aren’t busy with models. That would be so-called “climate scientists”, ie computer gamers who often aren’t scientists at all, but like Gavin, mathematicians.

Scientists do study the origin and evolution of Earth’s atmosphere, but there isn’t as much evidence as they’d like.


First atmosphere:

Atmospheric N2 evolution on Earth and Venus:

Importance of CO to atmospheric evolution:

Fossil raindrops from 2.7 Ga:

Biological regulation before oxydation:


Biological limit on O2 increase during the “Boring Billion”, which really wasn’t dull:

Could post more, but am probably already going to be even further delayed by moderation.

John Tillman
Reply to  Ed Zuiderwijk
December 12, 2019 7:35 am

Early atmosphere was once thought to have been highly reducing, but now is generally considered to have been more weakly reducing, ie with oxygen-containing compounds as substantial components. So, instead of dominated by CH4, NH3, N2, H2, etc, the best evidence suggests Hadean airconsisted mostly of carbon dioxide, with smaller amounts of methane, ammonia, nitrogen, sulfur dioxide and water vapor. The upper atmosphere might have contained ozone, produced by the then higher UV flux breaking up water molecules.

The light H2 was lost to space.

Basically, early air was made up of volcanic gas emissions.

Zig Zag Wanderer
Reply to  Ed Zuiderwijk
December 12, 2019 9:45 pm

Martian atmosphere is thin, only 1% of the Earth’s. Even at 100% CO2 it is practically transparant, incapable of trapping radiant heat.

The CO2 in our atmosphere is only 0.04%.

Mars’ CO2 is 95% of its atmosphere.

For CO2 content, Mars has the equivalent of 0.95% of our atmosphere, ie nearly 24 times the absolute quantity of CO2 as we do (per unit of area).

Therefore if what you say is true, our CO2 is 24x less able to trap heat. 24x less than “incapable”.

Obviously there is something else causing our planet to be warmer. How about being closer to the sun and having water in our atmosphere?

Tom Abbott
December 12, 2019 5:25 am

Why does Venus have such a large amount of CO2?

Reply to  Tom Abbott
December 12, 2019 5:32 am

One possibility is that it was never sequestered into limestone rocks and carbon deposits as on Earth.

John Tillman
Reply to  Tom Abbott
December 12, 2019 5:45 am

Way and Del Genio argue that it’s because of the resurfacing event some hundreds of millions of years ago. But Mars has a 95% CO2 atmosphere, while Earth also had a high CO2 concentration early in its history.

Part of the story on both Mars and Venus is the loss of water. Earth, by contrast has held onto its water and produced O2, while life processes and carbonate rock formation have drawn down CO2. Our planet also maintains CO2 in its seas rather than just in the air.

Despite its 96% CO2 concentration, Venus’ air also has over three times as much nitrogen as Earth’s (about 3.5% of Venusian atmosphere).

Tom Abbott
Reply to  John Tillman
December 12, 2019 1:52 pm

Thanks for the explanations and all those links, John. Very helpful.

John Tillman
Reply to  Tom Abbott
December 12, 2019 3:12 pm

Glad you found them helpful.

I gathered a lot of links for an intended post on the reasons for Venus’ heat. But comments on this post pretty much cover most of what I was going to argue.

John Tillman
Reply to  John Tillman
December 14, 2019 1:53 pm

Hard to compare N2 content of Earth’s and Venus’ air early in their histories, obviously.

But Venus’ higher concentration could result from mantle oxidation after atmospheric water loss.

Ed Zuiderwijk
Reply to  Tom Abbott
December 12, 2019 5:56 am

The surface temperature is such that carbonates dissociate into their oxides and CO2. Where on Earth enormous quantities of CO2 are sequestred as carbonates CaCO3 (limestone) and MgCO3, on Venus these compounds are unstable. Hence the carbondioxide remains unbound in the atmosphere.

Reply to  Tom Abbott
December 12, 2019 6:21 am

I presume you are asking as compared to Earth. There are two reasons.

First, Venus also has 4 times more nitrogen than Earth. Assuming both planets started out at roughly the same size and chemical makeup, this implies that Earth lost around 3/4 of it’s atmosphere in the collision that formed the moon.

Secondly, almost all of Earth’s remaining primordial CO2 combined with oxides in the oceans to form carbonates. Most of the rest was removed biologically. Any oceans originally on Venus did not survive long enough to chemically remove the CO2.

John Tillman
Reply to  ScarletMacaw
December 12, 2019 6:41 am

A quibble, but it’s actually closer to three times as much N2, ie 0.035 X 91 = 3.2 times as much nitrogen, where Venus’ atmospheric pressure is some 91 times Earth’s, with 3.5% N2 in Venusian air. The planets are close enough to the same size to neglect that factor.

Tom in Florida
Reply to  ScarletMacaw
December 12, 2019 7:19 am

Thirdly, Venus does not have any magnetic fields to shield if from the solar wind.

Robert W Turner
Reply to  ScarletMacaw
December 12, 2019 7:29 am

Gases are dissolved into Earth’s oceans.

Tom Abbott
Reply to  ScarletMacaw
December 12, 2019 1:56 pm

Ok, I didn’t take into account the partial loss of Earth’s atmosphere from the early collision. Thanks.

Reply to  ScarletMacaw
December 12, 2019 6:56 pm

Another factor, as though one is needed – thanks to the collision, Earth’s crust is between 25% and 50% thinner than the Venusian crust. (Estimates vary widely; and I hope that the idea of “balloon seismometers” pans out – we certainly aren’t going to see a Mohole project on Venus!)

Thinner crust, higher tidal stresses, more tectonic activity, including subduction of carbon compounds into sequestration in the deep crust. (I can’t find much on the CO2 removal effect of chemical weathering of upthrust – new mountains – by interaction with the carbonic acid in rainfall – but I don’t think that removes all that much CO2 on Earth, and obviously none is removed in that manner on Venus.)

December 12, 2019 6:09 am

“Now superheated by greenhouse gases”

Sort of. The surface is primarily heated by adiabatic compression… the surface of Venus receives no light and therefore cannot have a “greenhouse effect,” that all happens way up in the atmosphere, plus note Venus has a much higher albedo than Earth anyway.

At the Venusian surface, it’s the adiabatic lapse rate that is far different than Earth’s, not the greenhouse effect.

December 12, 2019 6:09 am

“Now superheated by greenhouse gases”

Sort of. The surface is primarily heated by adiabatic compression… the surface of Venus receives no light and therefore cannot have a “greenhouse effect,” that all happens way up in the atmosphere, plus note Venus has a much higher albedo than Earth anyway.

At the Venusian surface, it’s the adiabatic lapse rate that is far different than Earth’s, not the greenhouse effect.

See Venus Envy here on WUWT.

Bloke down the pub
December 12, 2019 6:28 am

If they’re trying to power balloons but can’t use solar pv because of the thick cloud, why not take advantage of the strong winds to power turbines?
On a separate thought, geo-engineers have suggested using orbital mirrors to control the temperature on Earth. Wouldn’t they work better on Venus?

Robert W Turner
Reply to  Bloke down the pub
December 12, 2019 7:33 am

It’s too hot for wind turbines at the surface. It would be interesting to see the math on it though – at 93 bar and 460 C the frictional heating on those blades would be enormous.

Bloke down the pub
Reply to  Robert W Turner
December 13, 2019 9:28 am

They’d be on balloons, flying at an altitude more conducive to the equipment surviving.

Reply to  Bloke down the pub
December 12, 2019 7:09 pm

Your free flight balloons would be moving with the wind. Wind velocity would therefore be very close to zero (not quite zero, due to friction, but useless for turbines).

On terraforming Venus. Paraphrasing Robert Heinlein, all you need to do is move the planet into Earth’s orbit (please make sure you allow a very large windage on that), strip it of just about all of it’s atmosphere, dump a few thousand ice cubes (comets) onto it, seed it with high temperature algae, and let it marinate for somewhere between ten and one hundred million years.

Then you open up your real estate office to sell Texas sized lots to the distant descendants and inheritors of Gates, Turner, Bloomberg, etc.

Reply to  Writing Observer
December 13, 2019 6:37 am

You don’t want to strip the atmosphere, you’ll need it for the carbon cycle.

Shading would be step 1. As temperatures (very slowly, remember that adiabatic lapse rate!) drop, in go the comets. Now that you have a bit of hydrogen, we can start to lock all that carbon into rocks, hopefully with genetically-engineered microbes or something else that scales well and quickly and doesn’t require much hydrogen.

Surface might even be human-survivable (in high-altitude habitats, in conditions similar to a fairly shallow basin in an Earth ocean — 90 bars is about 3000 feet of ocean, avg depth is 14000) in a mere few thousand years, if energy use was no object. Depends how fast it cools, I guess.

Good wiki

Bloke down the pub
Reply to  Writing Observer
December 13, 2019 9:33 am

I’d expect wind speed to vary with altitude, so suspend the turbine from a tether and the difference in wind speed should be similar to the range utilized by Earthbound turbines.

Nicholas Schroeder
December 12, 2019 7:43 am

Venus, we are told, has an atmosphere that is almost pure carbon dioxide and an extremely high surface temperature, 750 K, and this is allegedly due to the radiative greenhouse effect, RGHE. But the only apparent defense is, “Well, WHAT else could it BE?!”

Well, what follows is the else it could be. (Q = U * A * ΔT)

Venus is 70% of the Earth’s distance to the sun, its average solar constant/irradiance is about twice as intense as that of earth, 2,602 W/m^2 as opposed to 1,361 W/m^2.

But the albedo of Venus is 0.77 compared to 0.31 for the Earth – or – Venus 601.5 W/m^2 net ASR (absorbed solar radiation) compared to Earth 943.9 W/m^2 net ASR.

The Venusian atmosphere is 250 km thick as opposed to Earth’s at 100 km. Picture how hot you would get stacking 1.5 more blankets on your bed. RGHE’s got jack to do with it, it’s all Q = U * A * ΔT.

The thermal conductivity of carbon dioxide is about half that of air, 0.0146 W/m-K as opposed to 0.0240 W/m-K so it takes twice the ΔT/m to move the same kJ from surface to ToA.

Put the higher irradiance & albedo (lower Q = lower ΔT), thickness (greater thickness increases ΔT) and conductivity (lower conductivity raises ΔT) all together: 601.5/943.9 * 250/100 * 0.0240/0.0146 = 2.61.

So, Q = U * A * ΔT suggests that the Venusian ΔT would be 2.61 times greater than that of Earth. If the surface of the Earth is 15C/288K and ToA is effectively 0K then Earth ΔT = 288K. Venus ΔT would be 2.61 * 288 K = 748.8 K surface temperature.

All explained, no need for any S-B BB LWIR RGHE hocus pocus.

Simplest explanation for the observation.

John Tillman
Reply to  Nicholas Schroeder
December 12, 2019 8:55 am

The formula doesn’t work for Mercury, whose atmosphere is so negligible as to be ignored.

Mercury’s average solar irradiance is 9082.7 W/m^2, with Bond albedo of 0.068, for effective insolation of 8465.1 W/m^2. Earth’s average irradiance is 1361.0 W/m^2, with Bond albedo of 0.306, for effective insolation of 944.5 W/m^2. Thus, Mercury should be 8.96 times hotter than Earth. But it isn’t.

Mercury’s mean surface temperature is 440 K, ie hotter than Earth’s alleged 288 K. However, its highest surface temperature is about 740 K, while its lowest is around 90 K. But even at its hottest, Mercury is far from nine times Earth’s average temperature.

Did I leave something out of the equation?

John Tillman
Reply to  Nicholas Schroeder
December 12, 2019 9:47 am

Simplest explanation is also likely the main reason, ie that Venus turns 257 times more slowly than Earth, and that thick atmosphere keeps the night side warm during its 243 days of darkness.

December 12, 2019 8:42 am

“Now superheated by greenhouse gases …”

I call BS. Venus has always been hot and not as a result of the GHG effect. Earth never had a 90 bar CO2 atmosphere. If we took all the carbon on Earth and turned it back into CO2, the atmosphere would be far less than 2 bar, most of which would still be N2. If Earth was like Venus in the past, where did all the carbon go and how did life ever arise?

John Tillman
Reply to  co2isnotevil
December 12, 2019 2:01 pm

I agree with BS that Venus is hot because of CO2, but putting all the carbon dissolved in water, bound in organisms, carbonate rock and fossil fuels, back into Earth’s air, combined with oxygen, would far more than double atmospheric pressure.

Estimates of CO2 in Earth’s first atmosphere range from ten to 200 times more than now, but those estimates are suspect, as relying on GHGs to solve the supposed Faint Young Sun paradox. However, estimates based upon the actual amount of bound carbon reach similar or even higher levels.

December 12, 2019 8:44 am

Reflective mirrors in space? Most of our planet is covered in reflective clouds and 3/4 of it is covered in reflective water… If this much reflective surface isn’t enough, nothing imagined by mankind could ever do better. The infrastructure of covering the earth from space would take a considerable amount of mass of the moon with more surface area than all the continents on earth. Look at Saturn, the rings have a considerable amount of mass and yet reflect or block very little sunlight from the planet surface.
Strong winds spinning turbine on Venus? The surface air is more like a liquid then a gas. A very slow wind would move boulders tossing and crushing any windmill like a toy. A vaned balloon, free floating in the air, can spin with a pendulum inside generating a small amount of power. Far better to have a floating city above the winds for sunlight for photosynthesis to convert the carbon dioxide into food releasing oxygen to terraform the planet.

“Venus isn’t the closest planet to the Sun, but it is the hottest in our solar system.”

Venus is the fifth hottest planet in our solar system.
Jupiter by far is the hottest. In the transition layer, where the atmosphere turns from a gas to a liquid, it’s near 18,000°F. It is lectrified plasma twice as hot as the surface of the sun. Friction from pressure generates more heat the deeper you go, 64,000°F near the core.
Saturn is also hot broadcasting 2 1/2 times more heat than a receives from the sun.
Next is Neptune, the furthest from the sun. Then Uranus with temperatures near 9000°F about the same as the Sun’s photosphere.
The suns heat on the upper atmosphere of Venus is near 400°F and yet just under the sulfuric clouds, the temperature has been measured at -200°F, colder than anywhere on earth. Venus surface averages 860°F (900° F in the deepest Canyons due to more pressure) this extreme temperature variation is difficult to explain without violating the laws of thermodynamics.

10% of the crust of the earth is lime stone, calcium carbonate. Fossilized bones of ancient life that ate our once carbon dioxide atmosphere and sequestered it in stone. Life is the reason our planet is not like Venus. It is also the reason for our oxygen which when combined with hydrogen from the sun makes water. Every time you see the aurora borealis, you’re witnessing gases from the sun combining with oxygen creating millions of tons of water slowly making our ocean level rise. This also explains the O-Zone hole every September as the polar stratospheric clouds from space burn off with the first rays of sunlight in an arctic spring causing the ice cap to be thicker at the same time. Cause-and-effect will trump theories and models every day of the year.

John Tillman
Reply to  Max
December 12, 2019 9:10 am

James “Venus Express” Hansen once thought that the sulfuric acid clouds would enhance the warming greenhouse effect, whereas in fact they shade the surface. So well do they reflect sunlight that directly underneath them, it’s remarkably cold. The temperature differential might help drive the fast Venusian winds.

The clouds also mask a gigantic, planet-spanning gravity wave.

Keith Rowe
December 12, 2019 8:51 am

I have a problem with “Now superheated by greenhouse gases, Venus’ climate was once more similar to Earth’s, with a shallow ocean’s worth of water.”

My thoughts on this are that it never had a chance to cool. With a blanket of 90 bar of CO2 it just had a blanket wrapped around it for billions of years and finally cooled enough to have a good skin about 600 million years ago. There is no evidence of water on Venus, the hypothesis is based on no evidence other than the thinking that the Earth and Venus were the same start. But Venus has almost no rotation, no moon, has little ability to shed energy but through radiation which is severely limited by the 90bar blanket of CO2. The hypothesis should be easily shaken by almost zero rotation, almost no heat variation on the planet except at the upper atmosphere, and 70% light reflection provided by the Sulphuric Acid in it’s clouds making it appear super bright white. None of this is coherent with the idea Venus was Earthlike in any way we currently know it.

I always found it odd the way they describe in scientific journals that Venus is the hottest planet in the Solar System. Venus is 480 degrees C at surface but is 73 degrees at 1 bar. 1 bar – Earth atmospheric pressure at sea level is what the measure Jupiter and Uranus and all the other gas planets to determine which is the hottest and coldest.

John Tillman
Reply to  Keith Rowe
December 12, 2019 10:48 am

I agree that Venus has always been too hot for surface water, regardless of when its crust cooled enough to form solid rock.

The highest temperature eruptions on Earth today reach about 1500 K (2240 degrees F), but hotter lava erupted billions of years ago. It’s possible that Venus’ primordial lava surface could have reached 2000 K, depending upon chemical composition of the molten rock. Assuming a 91 bar atmosphere then as now, its cooling to a crust could have indeed taken a long time, but maybe not three billion years or more.

Interesting thought, though.

December 12, 2019 9:23 am

Interesting thing about the Venusian atmosphere at the surface. At 91 bar and 450C, it is a supercritical fluid, meaning that at the surface, it might be more of an ocean than an atmosphere. Cheers –

Roger welsh
December 12, 2019 9:46 am

Please will this writer define “greenhouse gas” and use the accurate word “difficult” when following fashion for ” challenging”!

Scientists do exist somewhere!

December 12, 2019 10:04 am

Question – Venus is described as “volcanically active”, how much heat can be released by that? I would guess that solar tidal effects would be causing some of that, but not sure of other things that could. Any help from the geologists? thanks!

Joel O'Bryan
December 12, 2019 11:34 am

Venus is not a runaway Green House in any sense of how the GHE operates on Earth wavelength dependent transparency. Very sunlight reaches the surface or the last few km above it.
Plus there is Venus’s very slow retrograde rotation (243 days) to further complicate energy dispersal unlike the rapid dirunal heating-cooling cycles as they occur on Earth, Mars.

Trying to see Venus as a runaway GH analog to Earth is so absolutely wrong, to claim that it is, is pure deception with an agenda.

Mayor of Venus
December 12, 2019 12:30 pm

A proposal to float balloons in Venus’ atmosphere as if that were a new idea? Has NASA forgotten it’s own history along with everyone else? It’s been done….the Vega 1 and Vega 2 missions….a joint effort of NASA and the Soviets, arrived at Venus June 1985 (almost 35 years ago). A lander and a helium balloon each, the balloons floated at 34 miles above the surface, where the temperature is near room temperature, and survived about 4 earth days.

December 12, 2019 12:36 pm

Venus has negligible magnetic field intensity and super hot climate. Earth has moderate magnetic field and a moderate climate. As the Earth’s magnetic field gets weaker climate warms and vice versa, i.e. there is a strong negative correlation as shown here

Steve Z
December 12, 2019 1:02 pm

“Venus is like the control case for Earth,” said Smrekar. “We believe they started out with the same composition, the same water and carbon dioxide. And they’ve gone down two completely different paths. So why? What are the key forces responsible for the differences?”

Venus and Earth have nearly similar diameters, masses, and gravity, but that’s where the similarity ends. Venus also receives twice the solar radiation of Earth, so that it would be hotter than Earth even if its primordial atmosphere was similar to that of Earth.

I don’t believe that Venus “started out” with the same amount of water as on Earth. If the surface atmospheric pressure on Venus is 90 atmospheres (about 1323 psi), liquid water could exist at up to 580 F in equilibrium at that pressure, but if there was much less liquid water available on Venus than on Earth when Venus formed, it would have all evaporated if the surface temperature was above 580 F.

Water vapor is also a greenhouse gas (more so than CO2), so if the primordial high-pressure Venusian atmosphere contained a lot of water vapor, it could have trapped enough heat so that the Venusian atmosphere was too hot to condense water, even at high pressure. Without any rain to replenish it, a Venusian ocean could have evaporated away.

It is also a stretch to believe that Venus “started out with the same carbon dioxide” as Earth–it probably had much more carbon dioxide than Earth. Assuming a current concentration of 400 ppm, the partial pressure of CO2 at sea level on Earth is about 0.0059 psi. If the total pressure of the atmosphere on Venus is 1,323 psi, even 10% CO2 would be a partial pressure of 132 psi, or more than 22,000 times the value on Earth. Where would all that CO2 come from, if it wasn’t there to begin with?

The article also talks about “corrosive sulfurous clouds” in Venus’ atmosphere, whereas Earth’s atmosphere contains very little sulfur-containing gases. Since sulfur-containing gases (H2S, SO2, SO3) are toxic to life on Earth, if the primordial atmosphere of the Earth contained as much sulfur as that on Venus, life probably would not have developed on Earth.

Earth’s atmosphere is very unusual among the planets of the solar system, with 78% nitrogen, which is chemically and optically inert, and 21% oxygen, required to sustain life but also relatively transparent in the visible and infrared spectra. Most of the outer planets have atmospheres rich in methane and/or ammonia, with very little nitrogen or oxygen, while Venus’ atmosphere is rich in CO2 and sulfurous gases. The Earth’s distance from the sun, combined with the greenhouse effect from water vapor, enable it to have large amounts of liquid water at the surface, for which the outer planets are too cold (water would freeze), and Venus and Mercury are too hot.

It is extremely unlikely that Earth’s atmosphere could become like that of Venus, unless there was some catastrophic change in the Sun, which would cause it to emit more than twice as much radiation as it does now.

John Tillman
Reply to  Steve Z
December 12, 2019 2:24 pm

As the Sun grows in power over the coming billions of years, at the rate of one percent per 100 million years, Earth will probably enter a “moist greenhouse” phase, in which surface water evaporates into the atmosphere, increasing pressure, hence allowing water to stay liquid at higher temperature, but eventually wetting the stratosphere, where UV light will break down H2O into its atoms, with the hydrogen being lost to space.

This is probably what happened to Venus from the start, ie it never had liquid water, despite high atmospheric pressure. But even if there were briefly liquid water on its surface, conditions were too hot for life to get started, with or without sulfur compounds. Chemosynthesis of sulfur compounds by microbes on Earth predated photosynthesis.

Venus most likely did have water in its primordial air, but lost it via photodissociation.

John Tillman
Reply to  John Tillman
December 12, 2019 3:29 pm

Make that 110 million years.

Reply to  John Tillman
December 12, 2019 7:18 pm

Thank you! 10% more time before I have to start getting seriously worried…

December 12, 2019 1:12 pm

PV=nRT explains the temp on Venus quite well. Thank you. Solve for T.

December 12, 2019 1:34 pm

This is yet another exercise by NASA in Science Fiction, containing such gems as: “Now superheated by greenhouse gases, Venus’ climate was once more similar to Earth’s, with a shallow ocean’s worth of water. ” ? It is yet another effort to bolster the failing GHG Global Warming theory.

December 12, 2019 3:57 pm

““Venus is like the control case for Earth,” said Smrekar. “We believe they started out with the same composition, the same water and carbon dioxide. And they’ve gone down two completely different paths. So why? What are the key forces responsible for the differences?””

Well… for a start let’s get rid of the “we believe” Across many years of interest I have yet to see ANY evidence to support the idea that Venus and Earth have ever been ‘twins’ – they share similar size and that’s it.

The lack of magnetic field for Venus (what is there is apparently generated by interactions between her ionosphere and the solar wind) has the interesting effect of demolishing one explanation for the lack of atmosphere on Mars. The solar wind is MUCH stronger for Venus and yet the lack of a strong mag field hasn’t caused Venus atmosphere to evaporate away into space.

But the elephant in the room is as obvious as the full moon in the night sky… OK, it’s the Moon. 😀 It is likely the interactions with the Moon have changed Earth’s atmosphere and allowed us to have something we can survive in.

Constant perturbation of the Earth’s oceans and crust would also have effects not seen on Venus.

And as a nice little aside, they still can’t really explain why the orbit of Venus is so circular. The implication from Occam is that Venus hasn’t been there long and the low probability of it somehow entering an orbit so perfect could easily lead to speculation about HOW it got there.

The orbit of the Sun and planets around the solar barycenter should have warped the orbit of Venus long ago if it has been there since year dot.

As for the ludicrous statements about the planet based on the tiny amount we have gleaned, they belong in the ‘pure speculation’ cupboard, rather than as a justification trotted out to organise yet more doomed missions to the planet. If they can’t do enough science to recognise the absurdity of trying to blame CO2 for the heat of Venus, they should not be designing the missions.

John Tillman
Reply to  MarkMcD
December 12, 2019 4:11 pm

Both Venus and Earth have nearly circular orbits, although Venus’ is more so than Earth’s, which is closer to Jupiter. Mercury has a highly elliptical orbit because of the Sun, while Mars does thanks to Jupiter.

An interesting observation is that Venus’ core appears to show a p = −5 spin‐orbit resonance with the Earth. We’re pretty close, so no surprise if we have a gravitational effect on each other.

IMO there is no reason to assume that Venus didn’t coalesce in its present position.

Sky King
December 12, 2019 4:32 pm

Let’s give Sue Smrekar her wish and send her to Venus.

December 12, 2019 7:01 pm

Mars is cold because the amount of heat convected from its surface and radiated to outer space at higher altitude is relatively greater than Venus. The pressure at Venus’ surface is high enough that there is hardly any wind, while 3/4 of the way up, where density density is lower, wind speeds are hundreds of km/hr, also moving the Sun’s radiant energy up to high enough altitude to radiate the heat to space through the relatively thick Venusian atmosphere, compared to Mars.

Nicholas Schroeder
Reply to  DMacKenzie
December 13, 2019 9:07 am

Mars is cold because it is farther away – period.

Rudolf Huber
December 13, 2019 2:40 pm

Venus a control case for Earth? Who is trying to fool us right now? Venus is on average 108 Million km away from the Sun. Earth almost 150 Million km. You don’t think that an additional more than 40 Million km makes a difference? The effect of solar radiation decreases exponentially with additional distance. So venus always received a lot more solar energy than Earth did. That may have prevented microbial life from forming which in turn prevented CO2 from being stored in solids. The Venusian atmosphere is not subject to a greenhouse effect. Its subject to a lot more solar energy and has an atmosphere to spread it over the surface day and night. Mercury is closer still but has no atmosphere so it heats up on the dayside and freezes on the night side. Venus is not like Earth – and has never been.

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