Venus Express press conference November 28th, Venus: a more Earth-like planetary neighbour Options

[belleraphon1]

All..

Venus Express press conference set for November 28th.

http://www.esa.int/esaCP/SEMX1C63R8F_index_0.html

‘Venus: a more Earth-like planetary neighbour’
Latest results from Venus Express
28 November 2007, 15:00, room 137
ESA Headquarters, 8-10 rue Mario-Nikis, Paris

15:00 Introduction, by Håkan Svedhem, ESA Venus Express Project Scientist
15:07 Venus: What we knew before, by Fred Taylor, Venus Express Interdisciplinary Scientist

15:15 Temperatures in the atmosphere of Venus, by Jean-Loup Bertaux, SPICAV Principal Investigator

15:25 The dynamic atmosphere of Venus, by Giuseppe Piccioni, VIRTIS Principal Investigator

15:40 Venus’s atmosphere and the solar wind, by Stas Barabash, ASPERA Principal Investigator

15:50 Climate and evolution, by David Grinspoon, Venus Express Interdisciplinary Scientist

16:00 Conclusion, by Dmitri Titov, Venus Express Science Coordinator and VMC scientist

16:05 Questions and Answers

16:25 Individual interviews

17:30 End of event

Craig

[belleraphon1]

Also...

The results will appear in a special section of the 29 November issue of the journal Nature containing nine individual papers devoted to Venus Express science activities.

HOT!!!!!

Craig

[cndwrld]

Press Conference Results

The press conference results, detailing the initial findings from Venus Express, are now posted on the web at

http://www.esa.int/SPECIALS/Venus_Express/...73R8F_0_ov.html

Putting all the instrument results together gives a pretty amazing picture of the atmosphere.

[nprev]

To say nothing of Venus' past. It looks as if ancient oceans are almost dead certain now; remarkable.

Lots of great things here; the lightning is really quite a find!

[Guest_Zvezdichko_*]

Venus Express is not the first spacecraft to detect lightning. The first probes to detect lightning and thunderstorms are Venera landers.

[tedstryk]

There was always controversy surrounding that. None of the orbiters/flyby spacecraft had found anything definitive, the short lifespans of the landers, and the extreme conditions they were under, there was some uncertainty as to whether some of the charges might be related to the spacecrafts themselves.

[JRehling]

There was always controversy surrounding that. None of the orbiters/flyby spacecraft had found anything definitive, the short lifespans of the landers, and the extreme conditions they were under, there was some uncertainty as to whether some of the charges might be related to the spacecrafts themselves.

Yes, if you just follow the headlines without reading between the lines, the story on venusian lightning reads: Yes there is; No there isn't; Yes there is; No there isn't; Yes there is. Cassini's team said that either Venus has no lightning, or if it does, it's really rare or really different than Earth's. Those hedges are possibly the key: Cassini's radio and plasma wave instrument said no. VEx's magnetometer says yes. These could be reconciled if there's lightning on Venus, but something totally blocks the radio/plasma signals (or there never are any), but the magnetic field comes through. My conclusion is that that is almost certainly the case. The only alternative would be that Venus sometimes has lots of lightning, but sometimes no lightning anywhere on the planet. That's hard to believe, verging on impossible to believe. Perhaps if volcanic ash clouds are the source of all lightning, that would be possible, with lightning depending upon eruptions. For now, that explanation doesn't stand up very well to Occam's Razor.

Venus has some pretty different atmospheric conditions from the "other" lightning planets (Earth, Jupiter, Saturn -- an unlikely trio), especially in that lacking a magnetic field, the thick atmosphere gets pounded by solar wind. Maybe that is the key distinction in the lack of radio/plasma detection.

I'm not sure if lightning on Venus has any ramifications other than

[edstrick]

CT Russell is one of the partisan participants in the "Lightning Wars". At an LPSC around 1990 or a bit earlier, two participants in the wars were basically calling each other liars and data fudgers (I have no recollectin who they were, now). It's been one of the most heated, but least illuminated battles in planetary science over the years, fueled by a woeful lack of definitive data.

I think VExpress is repeating plasma wave radio emission measurements similar to those pioneer venus made over extended periods, but with a vastly better instrument. Cassini made similar measurements to VExpress, but over a brief flyby. This round goes to the radio emissions geeks.

HOWEVER... that they look like lightning created impulsive discharges doesn't prove they are. What we still need is a high sensitivity wide angle camera that can take airglow and surface-glow limited time exposures of the nightside, accumulating pole-to-pole, dawn-to-dusk coverate in broadband visible wavelengths, and at wavelengths that probe into the shortest wavelenfth infrared windows. Coupled with impulsive flash detectors, similar to those on lightning detectors in earth orbit, we could map the global time and space distribution of whatever lightning appears to be on the planet. Till we have such a map, or negative results from a high sensativity optical/ir lightning detector (meteor observation capable, too), I'm going to continue to be skeptical on this claim.

I'm not disputing their results, I've just watched this war too long.

[Julius]

I am no planetary sceintist but just a humble enthusiast!I have a few queries maybe some of you could answer:

Why should Venus have a thicker atmosphere than Earth provided it lacks a magnetic field and hence being in direct contact with the solar wind ,which should produce higher rates of atmospheric loss.This seems to be the explanation for mars!?

The moon is said to be acting as a friction brake on Earths rotation and thus is slowing it down.Has anyone explained clearly why Venus is such a slow rotator in the absence of a moon!Could a previous collision of a cosmic body with Venus help to explain this . Venus was once(i think its about 500-800 million years ago) entirely resurfaced by hot magma .Could this have happened when this theorised collision took place?

Why should Venus lack a magnetic field given its the same radius and almost same density like Earth?Could it be that its dry compared to Earth ,simply explain for this significant difference?

[JRehling]

I am no planetary sceintist but just a humble enthusiast!I have a few queries maybe some of you could answer:

Why should Venus have a thicker atmosphere than Earth provided it lacks a magnetic field and hence being in direct contact with the solar wind ,which should produce higher rates of atmospheric loss.This seems to be the explanation for mars!?

The moon is said to be acting as a friction brake on Earths rotation and thus is slowing it down.Has anyone explained clearly why Venus is such a slow rotator in the absence of a moon!Could a previous collision of a cosmic body with Venus help to explain this . Venus was once(i think its about 500-800 million years ago) entirely resurfaced by hot magma .Could this have happened when this theorised collision took place?

Why should Venus lack a magnetic field given its the same radius and almost same density like Earth?Could it be that its dry compared to Earth ,simply explain for this significant difference?

That last question is a good one, and there is a lot of mystery still remaining. In my mind, sort of a chicken-egg problem:

Assuming Venus were initially proto-earthlike, but had lost most of its water, that would prevent CO2 from becoming locked up in carbonates (Earth and Venus actually have similar reservoirs of the C and the O, but on Earth it's tied up in rocks). That would give Venus the huge partial pressure of CO2 that creates the high temperatures, and the solar tides that can actually slow the planet's rotation. And presumably, a slower rotation could be a factor in the lack of a magnetic field. But why would Venus lose its water in the first place? If it initially lacked a magnetic field, then that allows solar wind to hit the upper atmosphere, which would speed the loss of H2O. And if it were initially hot, then that pushes more of the H2O into higher altitudes, also speeding the loss of CO2. But it's not clear how this process, with several self-reinforcing factors creating the modern Venus, was bootstrapped. Maybe Venus started without a magnetic field for some unknown reason. Maybe it started off with very slow rotation as a consequence of its accretion.

The solar wind does not remove a lot of CO2, however, because it's a heavy molecule and hard to break apart. H2O is easier to break apart, and when it does, the H escapes. Even if you broke CO2 apart, the C and O would still be apt to stay around, being heavier. Mars has a lower escape velocity, so it can lose nitrogen and CO2 at a non-negligible rate.

It is unlikely that a massive collision caused Venus's global resurfacing. We can see lots of worlds that bear the scars of past collisions, and they don't cover their tracks -- they leave big rimmed basins. I guess it's hard to falsify whether or not a modest collision could have been the trigger starting the process. But there are models to explain the resurfacing event, too. Basically, that Venus boils off its inner heat in a few, rare planetwide meltdowns, instead of letting a little out all the time like Earth.

While the right collision (or stage in the accretion, taking the form of one big lump coming in fast) might have played around with Venus's rotation, it is not a necessary or sufficient explanation. Venus's axis is very nearly aligned with its orbit, which would be unlikely to happen if a big random torque were applied. Dynamical models of tides raised in Venus's atmosphere by the solar heating on the dayside predict that the current rotation is one of two stable states. It must have taken a long time for this to halt the rotation if it were initially fast, but it may not have been fast. A collision/accretion event may have done part of the job, with solar tides doing the rest.

[hendric]

I am no planetary sceintist but just a humble enthusiast!I have a few queries maybe some of you could answer:

Why should Venus have a thicker atmosphere than Earth provided it lacks a magnetic field and hence being in direct contact with the solar wind ,which should produce higher rates of atmospheric loss.This seems to be the explanation for mars!?

The moon is said to be acting as a friction brake on Earths rotation and thus is slowing it down.Has anyone explained clearly why Venus is such a slow rotator in the absence of a moon!Could a previous collision of a cosmic body with Venus help to explain this . Venus was once(i think its about 500-800 million years ago) entirely resurfaced by hot magma .Could this have happened when this theorised collision took place?

Why should Venus lack a magnetic field given its the same radius and almost same density like Earth?Could it be that its dry compared to Earth ,simply explain for this significant difference?

My knowledge is fairly basic, but here is how I understand it.

Most, if not all, of your questions center around water. Venus had, presumable, similar amounts to Earth, but lost it. Initially it was probably in oceans. These dried up due to the heat as the Sun warmed. Water is a much better greenhouse gas than CO2, so it increased the temperature even more. As the atmosphere got saturated with water, more and more of the water was photodissociated to hydrogren and oxygen by the UV from the sun. The hydrogen escaped, leaving the oxygen. Over time, most of the water disappeared.

As the climate heated up, the rocks themselves lost their water and CO2. On earth, there is a great quantity on CO2 stored in rocks as carbonates etc. So even though there is more loss due to solar wind at Venus, there is just so much more atmosphere because all the stored CO2 has been released. Plus, Venus gravity is much higher than Mars. Also, for Mars there is a theory that oblique asteroid impacts "threw" parts of the atmosphere off of the planet.

As for the slow rotation, there are multiple theories there. The one I've heard is that the atmosphere itself could have cause the rotation to slow down and switch directions over eons, with solar tides playing a big factor. A previous collision is also possible, but would be hard to prove without evidence (like a Moon! ).


The resurfacing is, again, related to the lack of water. The current theory is that without water, the crust is less flexible, and much thicker. Because of that, the heat generated internally builds up to high temperatures before it gets hot enough to escape to the surface. When it does, I imagine Venus, under the atmosphere, would be covered with as many volcanoes as Io.

The lack of a detectable magnetic field is due to the lack of rotation. Assuming a similar composition to Earth, it would have a molten core with the appropriate convection currents. But because the planet doesn't rotate very fast, it cannot generate a magnetic field using a dynamo effect. How I visualize the internal dynamos is to think of spider silk floating in the air (these are the magnetic field lines). Imagine grabbing it with your hand, and start spinning your hand until it's covered in the silk. The closer the silk is to itself, the stronger the field lines. In the core the field lines are close, since the conductive molten iron grabs the lines tighter than the nonconductive rest of the earth. Because Venus doesn't spin very fast, it doesn't "catch" enough field lines to make a significant magnetic field. It's probable it does generate a very small magnetic field, just that it's too weak to get very far from the core.


I'm sure Emily can give us the straight answer on all these, being the Venus expert she is!

[JRehling]

I'm not sure if lightning on Venus has any ramifications other than

Oops. Cut myself off there. I meant to say, ... other than its own existence/nonexistence. Ie, I don't know if any putative lightning would actually do anything besides crackle and flash. On Earth, it creates ozone. Maybe lightning does/would leave some chemical footprints in the venusian clouds?

[Juramike]

It must have taken a long time for this to halt the rotation if it were initially fast, but it may not have been fast. A collision/accretion event may have done part of the job, with solar tides doing the rest.

I'm wondering if Earth is the exception of the two planets.

Perhap Earth got smacked by a large object (which we know it did at least once, e.g. forming the Moon), which caused an increased core rotation rate [is the Earths core symmetrical?], which induced a stronger magenetic field, which prevented water loss, which kept the tectonic plates lubed up and movin' and groovin', which helped bury CO2 (thanks to ocean chemistry), which kept our planet cooler and wetter and which made it just a much nicer surface on which to live on.

Venus, for some reason, never got a strong magnetic field. The atmosphere heated up, the water escaped, the tectonics locked up, the land dried out, then started to get sporadically resurfaced, and maybe tidal effects slowed down the rotation rate even further.

Venus might be the result of a "natural" vicious cycle common to terrestrial planets of that size in that orbital zone. In contrast, Earth is the wierd cousin that got dropped on it's head when it was young and was never "quite right" after that.

Maybe Venus is what Earth should look like if it hadn't been for a lucky strike or two?

-Mike

[nprev]

Let's not forget that there's a poorly understood connection between Venus & Earth as well. Venus presents its same "face" to us over its 243 "Earth-day"-day and 225-day orbital period. This synchronicity is unlikely to have arisen by accident.

Maybe we have a good twin/evil twin thing working here...careful, Venus may want revenge!

Seriously, though, to me this seems as if Venus had a very slow rotation period from the outset, and the fact that it comes fairly close to Earth (25 million miles) might have been just enough to brake its rotation into the current resonance. Maybe all that went wrong is that it didn't get smacked in the right way to get it spinning right (in fact, it probably got smacked the wrong way to slow it down in the first place.)

[elakdawalla]

I'm sure Emily can give us the straight answer on all these, being the Venus expert she is!

I wish I could, but what you've written is as much as -- or more than -- I know. In fact you might listen for some familiar-sounding words on an upcoming Planetary Radio program My expertise is pretty much limited to what happens at or beneath the surface. All that atmosphere is just a pesky obstruction to Venus' cool geology.

--Emily

[hendric]

Maybe Venus is what Earth should look like if it hadn't been for a lucky strike or two?

I don't think it's the lucky strike syndrome, but more "location location location". Once a terrestrial planet gets warm enough that it's H2O starts significantly evaporating, the endgame looks like Venus. In a billion years or so, once the Sun's output increases enough, Earth will rapidly evolve into a Venus near-twin.

The hardest part of this scenario to explain, for me, is why the massive cloud cover generated by an ocean starting to evaporate wouldn't block enough sunlight to keep it in equilibrium. I recall reading somewhere that the actual solar heat input at the surface of Venus is less than Earth due to the clouds, but the percentage kept is of course much higher.

Seriously, though, to me this seems as if Venus had a very slow rotation period from the outset, and the fact that it comes fairly close to Earth (25 million miles) might have been just enough to brake its rotation into the current resonance. Maybe all that went wrong is that it didn't get smacked in the right way to get it spinning right (in fact, it probably got smacked the wrong way to slow it down in the first place.)

I think the big player in Venus rotational evolution has got to be the Sun. Any effect from Earth would have to be very very small. That said, it's possible, and the fact that there is a very close synchronicity is interesting. But given that the other reasonably large objects in the inner solar system (excluding Mercury, but including Earth, Mars, Ceres and Vesta) have fast rotations, I'd lean towards Venus starting at a similar rate.

Here's a wild hypothesis. What if Venus was just like Earth, but never got hit by that last Mars-sized object to strip away it's outer crust & volatiles? Perhaps this left Venus with a <b>larger</b> amount of water than Earth, setting it up for a massive runaway greenhouse at the right time in the Sun's evolution? To be a worthwhile theory though, it needs to make a prediction...Umm, on the one piece of Venusian ground at the top of Maxwell Montes is a giant titanium sign written in Venusian that says "Don't burn carbon based fuels Earthlings".

All that atmosphere is just a pesky obstruction to Venus' cool geology.

Pesky obstruction? That atmosphere caused much of that cool geology, if present theories are accurate.

[Juramike]

Here's a wild hypothesis. What if Venus was just like Earth, but never got hit by that last Mars-sized object to strip away it's outer crust & volatiles? Perhaps this left Venus with a <b>larger</b> amount of water than Earth, setting it up for a massive runaway greenhouse at the right time in the Sun's evolution?

Wow! That's a really cool hot concept!

[Julius]

Wow! That's a really cool hot concept!

I kinda like that!AWESOME

[vjkane]

As I remember, one of the puzzles of planetary science is why the Earth has just enough water to fill its major basins but not flood the entire surface. Apparently, it would have been easy to have sufficiently more water to flood the entire surface. Perhaps this comes down to the special pleadings case: most earth like worlds that don't orbit too close to their star have entirely water covered surfaces. We are having this discussion only because we happen to be on one of the few that has significant exposed land.

[JRehling]

As I remember, one of the puzzles of planetary science is why the Earth has just enough water to fill its major basins but not flood the entire surface. Apparently, it would have been easy to have sufficiently more water to flood the entire surface. Perhaps this comes down to the special pleadings case: most earth like worlds that don't orbit too close to their star have entirely water covered surfaces. We are having this discussion only because we happen to be on one of the few that has significant exposed land.

Of course, if the Earth were sufficiently flat, there would be more than enough water to flood the surface, so the flip side is why the Earth has enough topography that some of it rises above the water. There could be a feedback system there: The diversification of new rock into lighter granite and heavier basalt possibly depending crucially on some crust being above water and some below.

Obviously, if the planet had 10 times as much water, or alternately 0.1 times as much, the topographical requirements to reach that feedback might be unattainable, but we might have a situation where the two nevertheless interact and create a larger attractor for some-land/some-sea.

[mcaplinger]

Of course, if the Earth were sufficiently flat, there would be more than enough water to flood the surface, so the flip side is why the Earth has enough topography that some of it rises above the water.

This is a significant part of the "Rare Earth" hypothesis of Ward and Brownlee.

http://en.wikipedia.org/wiki/Rare_Earth_hypothesis

[Tom Tamlyn]

So also is the existence of a large moon (product of the "big whack"), which stabilizes the earth's rotation.

TTT

This post has been edited by Tom Tamlyn: Dec 1 2007, 02:39 AM

[brellis]

The other day, I found a copy of David Grinspoon's Venus Revealed at the used book store. It's been on my night table since. Tomorrow, I'm going down to the magazine stand, hoping to find the new issue of Nature. I feel like a kid on Christmas eve!

[JRehling]

The other day, I found a copy of David Grinspoon's Venus Revealed at the used book store. It's been on my night table since. Tomorrow, I'm going down to the magazine stand, hoping to find the new issue of Nature. I feel like a kid on Christmas eve!

Venus Revealed is a very good read, which is almost entirely responsible for rekindling my childhood interest in astronomy here in the age of Internet coverage of space exploration. It captures a lot of the mystery of Venus, and is also very witty (Section titles like "Alternative Rock" and "But It's a Dry Heat"). About all of my childhood books on the planets were third-hand buys at garage sales, so all of the "upcoming opposition/maximum elongation" tables were far out of date by the time I got my hands on them. I emailed David and told him that I liked the idea of some kid in 2015 perceiving his book that way and he said he also had the outdated books as a kid and liked that idea, too.

This VEx release is also very stimulating, and offers a rare (for me; also this board) emphasis on atmospheric science, for a planet that's got quite a bit of one. Strange to say, but in some ways, Venus's atmosphere is the one in the solar system that most resembles ours (Titan is really the only other candidate). If you just start 60 km up, Venus's atmosphere has pressure/temperature curves that are pretty earthlike. I think a good outreach opportunity would be to format the gists of this issue into a Weather Channel program. If weather geeks can listen to analysis of the jet stream for 5 minutes, they might enjoy hearing about Venus's Hadley cells.

[edstrick]

Regarding the lack of magnetic field...

1)
Venus is smaller and less dense then Earth. This is partly, but models indicate not entirely, due to the lower compression of the interior due to the planet's lowre mass.
Venus also has a higher surface temperature than Earth. This raises the starting point for temperatures to rise due to the "geothermal" heat-flow as you go inward.

Models, as of maybe 15 years ago, indicated that Venus probably is not compressed enough and too warm for a solid, crystaline iron inner core to have started forming. This means the liquid core lacks a heat source from the freeze-out of the inner core and is considerably more stagnant than Earth's core, reducing convection that could drive a dynamo.

2)
The surface temperature is above the "curie point" of magnetic minerals that can hold a permanent magnetic field. There can't be magnetic anomalies like on Earth and Mars and the Moon from magnetic minerals in the crust.

these are additional points, adding to but not replacing above discussion of dynamo field generation.

[AndyG]

...at the top of Maxwell Montes is a giant titanium sign written in Venusian that says "Don't burn carbon based fuels Earthlings".

Wouldn't those metal snows on the tops of these mountains make lightning strikes probable, at the very least?

Andy (edit for spelling)

[JRehling]

Wouldn't those metal snows on the tops of these mountains make lightning strikes probable, at the very least?

Andy (edit for spelling)

I would guess that they would contribute almost zero. A cloud-ground discharge will take place if the resistance is overcome. Adding a thin layer of conductor doesn't reduce the total resistance (from air, mainly).

By analogy, it's like wondering if your money would go farther if an expense of zero were added to your budget. That neither hurts nor helps. If it REPLACED some other positive expense, then it would help. So a tall tower of copper might increase the probability of a lightning strike, but a thin flat layer shouldn't.

In any event, the best chance for lightning on Venus is cloud-cloud, with the resistance being a lot less than in the huge vertical groundtrack. There are no cumulus clouds on Earth ever nearly as high as all of the clouds are on Venus.

Even on Earth, I'm not sure that metal towers really increase the number of lightning strikes in a given locale significantly. Only to the extent that the height of the tower was a significant fraction of the cloud height (like the Empire State Building). Otherwise, they mainly just determine where it hits. (Eg, the tower instead of 20 meters north of the tower.)