Venus holds warning for Earth

Nov 30, 2010
Venus Express has two solar cell panels per wing comprising alternating rows of standard triple junction solar cells as well as highly reflective mirrors to reduce the operating temperatures. There is twice as much sunlight in Venus's orbit as there is in Earth's orbit, plus additional thermal input from the Venusian surface and atmosphere -- 75 percent of sunlight being reflected up from it. In certain cases, this results in Venus Express receiving an equivalent of the thermal input from 3.5 Suns. Credit: ESA

(PhysOrg.com) -- A mysterious high-altitude layer of sulphur dioxide discovered by ESA's Venus Express has been explained. As well as telling us more about Venus, it could be a warning against injecting our atmosphere with sulphur droplets to mitigate climate change.

Venus is blanketed in sulphuric acid clouds that block our view of the surface. The clouds form at altitudes of 50󈞲 km when sulphur dioxide from volcanoes combines with water vapour to make sulphuric acid . Any remaining sulphur dioxide should be destroyed rapidly by the intense solar radiation above 70 km.

So the detection of a sulphur dioxide layer at 90-110 km by ESA's Venus Express orbiter in 2008 posed a complete mystery. Where did that sulphur dioxide come from?

This video is not supported by your browser at this time.
This animation shows Venus, a planet very similar to Earth in mass and size, but in reality an entirely different, exotic and inhospitable world. It is hidden below blankets of dense clouds of noxious gases, such as carbon dioxide and sulphuric acid, and presents the most dramatic greenhouse effect taking place in the Solar System. Venus Express is helping to find out how a planet apparently so similar to Earth evolved in a way so radically different. Credit: ESA - C. Carreau

Now, computer simulations by Xi Zhang, California Institute of Technology, USA, and colleagues from America, France and Taiwan show that some sulphuric acid droplets may evaporate at high altitude, freeing gaseous sulphuric acid that is then broken apart by sunlight, releasing sulphur dioxide gas.

"We had not expected the high-altitude sulphur layer, but now we can explain our measurements," says Håkan Svedhem, ESA's Venus Express Project Scientist.

"However, the new findings also mean that the atmospheric sulphur cycle is more complicated than we thought."

As well as adding to our knowledge of Venus, this new understanding may be warning us that proposed ways of mitigating on may not be as effective as originally thought.

Nobel prize winner Paul Crutzen has recently advocated injecting artificially large quantities of sulphur dioxide into Earth's at around 20 km to counteract the global warming resulting from increased greenhouse gases.

The proposal stems from observations of powerful volcanic eruptions, in particular the 1991 eruption of Mount Pinatubo in the Philippines that shot up into Earth's atmosphere. Reaching 20 km in altitude, the gas formed small droplets of concentrated sulphuric acid, like those found in Venus' clouds, which then spread around Earth. The droplets created a haze layer that reflected some of the Sun's rays back into space, cooling the whole planet by about 0.5°C.

However, the new work on the evaporation of sulphuric acid on Venus suggests that such attempts at cooling our planet may not be as successful as first thought, because we do not know how quickly the initially protective haze will be converted back into gaseous sulphuric : this is transparent and so allows all the Sun's rays through.

This false-colour ultraviolet image of the south pole of Venus was obtained by the Venus Monitoring Camera (VMC) on board ESA’s Venus Express on 25 February 2008 from a distance of about 20 000 km, at a wavelength of 365 nanometres. The octagonal shape of the image is due to the VMC field of view. It is a zoom-in on the south polar ‘cap’, located inside a 60-degree-latitude circle. It shows a very bright and uniform appearance and lacks small-scale markings. However several global dark streaks usually cross the polar regions and seem to indicate strong jet-winds in the atmosphere around the pole. Credits: ESA/MPS/DLR/IDA

"We must study in great detail the potential consequences of such an artificial sulphur layer in the atmosphere of Earth," says Jean-Loup Bertaux, Université de Versailles-Saint-Quentin, France, Principal Investigator of the SPICAV sensor on Venus Express. "Venus has an enormous layer of such droplets, so anything that we learn about those clouds is likely to be relevant to any geo-engineering of our own planet."

In effect, nature is doing the experiment for us and Express allows us to learn the lessons before experimenting with our own world.

Explore further: NASA picks Boeing and SpaceX to ferry astronauts

More information: Photolysis of sulphuric acid as the source of sulphur oxides in the mesosphere of Venus, by Xi Zhang, Mao-Chang Liang, Franck Montmessin, Jean-Loup Bertaux, Christopher Parkinson and Yuk L. Yung, is published in Nature Geoscience today.

Related Stories

New details on venusian clouds revealed

May 30, 2008

As ESA's Venus Express orbits our sister planet, new images of the cloud structure of one of the most enigmatic atmospheres of the Solar System reveal brand-new details.

Sulphur-eating bacteria limit acid run-off and CO2

Jan 15, 2010

(PhysOrg.com) -- Acid Mine Drainage (AMD) is caused when sulphur in mine tailings reacts with water and oxygen in the environment to produce sulphuric acid. It is a major environmental issue, with AMD a concern ...

Recommended for you

Image: Crescent Mimas

13 hours ago

A thin sliver of Mimas is illuminated, the long shadows showing off its many craters, indicators of the moon's violent history.

User comments : 15

Adjust slider to filter visible comments by rank

Display comments: newest first

dtxx
1.4 / 5 (10) Nov 30, 2010
Love the AGW hook.
LariAnn
2.3 / 5 (6) Nov 30, 2010
I'm curious - if the sulphur dioxide reflects sunlight back into space, thus yielding the net effect of cooling the planet, and if 75% of sunlight is also reflected up from the planet, then how is it that Venus could be so hot? As stated in the first picture caption, there is twice as much sunlight in Venus's orbit as in Earth's orbit. If 75% of that is reflected up from the planet's surface, then only 50% of the amount of sunlight the Earth receives actually impacts the surface of Venus. So unless Venus is in a constant state of volcanic paroxysms, where is all the alleged heat coming from to make the surface of Venus like Crematoria in "The Chronicles of Riddick"?
NotAsleep
5 / 5 (8) Nov 30, 2010
@ LariAnn, I believe the answer is that even though it absorbs less sunlight it retains MORE heat from the sunlight due to the greenhouse gasses
Ratfish
1 / 5 (3) Nov 30, 2010
I expected it to be some global warming charlatan who was advocating injecting massive amounts of sulphur dioxide into the atmosphere but then I see it's a Nobel Prize winner. Lovely.
Sean_W
1.2 / 5 (10) Nov 30, 2010
@ LariAnn, I believe the answer is that even though it absorbs less sunlight it retains MORE heat from the sunlight due to the greenhouse gasses


While that sounds right at first, I am not so sure it is. There is a LOT less water vapor in the Venusian atmosphere and water is the big tamale of greenhouse gases. Those who are alarmed about potential climate change see CO2 and other gases from industry as tipping a "balance" which causes more heat to cause more water vapor which drives a self-reinforcing cycle. If Venus had the same pressure of atmosphere as earth, the extra sunlight would be offset by less water vapor as a greenhouse gass; resulting in a cooler planet. Venus is such a hot world, i suspect, mainly because of the very high pressure of it's more bountiful atmosphere.
Sean_W
1.3 / 5 (6) Nov 30, 2010
As stated in the first picture caption, there is twice as much sunlight in Venus's orbit as in Earth's orbit. If 75% of that is reflected up from the planet's surface, then only 50% of the amount of sunlight the Earth receives actually impacts the surface of Venus. So unless Venus is in a constant state of volcanic paroxysms, where is all the alleged heat coming from to make the surface of Venus like Crematoria in "The Chronicles of Riddick"?


Higher gas pressure means a higher temperature when the equilibrium between incoming and outgoing energy is reached, I think. See comment above.
Parsec
5 / 5 (8) Nov 30, 2010
Love the AGW hook.

The reference was to recently observed climate changes. NOT human caused global warming. Even if you ignore all of the evidence that the current warming trends are caused by human activities, the evidence that change is happening for SOME reason is overwhelming to anyone paying attention.
NotAsleep
1 / 5 (5) Nov 30, 2010
@ SeanW, I think water is only the big tamale in Earth's atmosphere. If we could sustain Suplphur Dioxide (instead of it turning into acid rain) I think it would end up being a bigger problem. i.e. if a volcano emmitted a continuous stream of SO2.

Thoughts?
jamey
2 / 5 (6) Nov 30, 2010
I think this kind of thing goes to show that the climate models the climatologists are using are not as solid as they'd like to claim they are.
Pyle
3.3 / 5 (7) Nov 30, 2010
If you have a question, look it up. Share what you find if it is pertinent, but don't just ask lame questions without looking for the answer first. You are commenting on a website. You should be able to use a search engine.

Here is a website with some information. (Google, 1st hit) It is on the Internet so it must be true!
http://starryskie..._hot.htm

Anyway, carbon dioxide is the "big tamale" on Venus.
MorituriMax
2 / 5 (3) Dec 01, 2010
Parsec,
Love the AGW hook.

The reference was to recently observed climate changes. NOT human caused global warming. Even if you ignore all of the evidence that the current warming trends are caused by human activities, the evidence that change is happening for SOME reason is overwhelming to anyone paying attention.


Really?

"As well as telling us more about Venus, it could be a warning against injecting our atmosphere with sulphur droplets to mitigate climate change."

Certainly looks like it is warning against activities we could engage in to me.
Shootist
1 / 5 (9) Dec 01, 2010
Distance from Sun to Venus: 108 million kilometers.
Distance from Sun to Earth: 149 million kilometers.

Venus holds no warning for Earth.
wwqq
5 / 5 (5) Dec 01, 2010
At that distance Venus should be recieving only 1.90 times the solar insolation of Earth, using the inverse square law.

But the radiant emittance is proportional to temperature to the fourth power according to stefan-Boltzmann's law; so if Venus had the same emissivity, albedo and atmospheric composition as Earth it should have a temperature of the fourth root of 1.90 = 1.17 times that of Earth.

The mean temperature of Earth is 287 K. The mean temperature of an Earth-like Venus should be ~337 K; but in actuality it is 726 K. The difference is attributable to the truly enormous greenhouse effect on Venus.

Mercury has a distance of only 46 to 70 million kilometers(eccentric orbit) from the sun, but its mean temperature is only 340 K. It has effectively nill greenhouse effect.
jsa09
5 / 5 (1) Dec 06, 2010
I was hoping no one was taking that idiot that wants to pollute the earth with sulphuric acid seriously. Seems I was wrong.
Olivia
not rated yet Dec 14, 2010
I'm curious - if the sulphur dioxide reflects sunlight back into space...


@ LariAnn SO2 is transparent to infrared, but H2SO4 is reflective. H2SO4 is what we want. In the upper surface of H2SO4 clouds, some H2SO4 evaporates and travels upwards to regions where ionising radiation would split it (H2SO4) into SO2, which is unwanted. The point is scientists are concerned about the residence time of H2SO4 for economical reasons (we have plenty of sulphur derived from petroleum) and they thought that SO2 should not be residing in the atmosphere indefinitely, but as we see in Venus, it (SO2) stays there forever (70km), which can be a highly irreversible geoengineering (climate engineering).