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Venus's Missing Water
December 29, 2008 9:26 PM   Subscribe

Where did Venus’s water go? Water may have once been as abundant on Venus as it is on Earth. New data from the Venus Express suggests that the planet's lack of a magnetic field has allowed water in the atmosphere to be stripped apart and carried into space by the solar wind.
posted by homunculus (30 comments total) 1 user marked this as a favorite

 
Previous post on the Venus Express.
posted by homunculus at 9:37 PM on December 29, 2008


That seems to have been what happened to most of the water on Mars, too.
posted by Chocolate Pickle at 9:41 PM on December 29, 2008


Commies stole its precious heavenly bodily fluids.
posted by orthogonality at 9:46 PM on December 29, 2008 [4 favorites]


VENUS NEEDS MAGNETS!
posted by The Whelk at 10:19 PM on December 29, 2008 [1 favorite]


By the way, Venus has been particularly bright recently in the southwest sky during the early evening, which leads it to be mistaken for the Christmas star.

If you live in a dense urban environment where you aren't used to enjoying the night sky, go out and look at Venus! It's bright enough now to cut through the light pollution.
posted by twoleftfeet at 10:26 PM on December 29, 2008


And don't forget to vote for Sarah Palin in 2012 for Interplanetary Overlord. She can see Venus from her house!
posted by twoleftfeet at 10:30 PM on December 29, 2008


twoleftfeet writes "If you live in a dense urban environment where you aren't used to enjoying the night sky, go out and look at Venus! It's bright enough now to cut through the light pollution."

Wait you mean those things up in the sky are actually lights coming from space?
posted by mullingitover at 10:33 PM on December 29, 2008 [2 favorites]


Wait you mean those things up in the sky are actually lights coming from space?

Can you nuke space from space just to be sure?
posted by maxwelton at 11:31 PM on December 29, 2008 [1 favorite]


Hey, why doesn't Venus have a magnetic field? And what 'caused the Earth to have one and not Venus?
posted by Brandon Blatcher at 3:54 AM on December 30, 2008


Apparently, possibly due to its size, or other characteristics, Venus lacks plate tectonics and other characteristics that cause a fluctuation in its iron core that cause a magnetic field to be generated. It's like having the dynamo sitting right there, but not being able to turn it on. Funny, considering that Earth isn't that much larger than Venus, but I guess it's also sorta confirmation bias, since if things hadn't been just right here, we wouldn't be posting on MeFi.
posted by explosion at 4:20 AM on December 30, 2008


I guess it's also sorta confirmation bias, since if things hadn't been just right here, we wouldn't be posting on MeFi.

Obviously you've never checked out the Venusian community weblogs. They're full of humor about the ridiculous ways of the blue planet.
posted by twoleftfeet at 4:28 AM on December 30, 2008 [1 favorite]


if things hadn't been just right here, we wouldn't be posting on MeFi

MeFipocentric Theory.

Delva and colleagues must also detect the loss of oxygen atoms on the day-side and verify that there are approximately half as many leaving Venus as hydrogen. So far, this has not been possible. “I keep looking at the magnetometer data but so far I can’t see the signature of oxygen escaping on the day-side,” says Delva.

Assuming the sensor is suited to finding oxygen in the data, this actually sounds like it disproves the theory.

In any case, I don't think I understand the theory. If the solar wind is ripping apart water and blowing away the hydrogen and oxygen, why isn't it also ripping apart the carbon dioxide (which makes up 97% of the atmosphere) and blowing away the carbon and oxygen, leaving a bare rock?
posted by DU at 4:33 AM on December 30, 2008


Life on Venus
posted by Pollomacho at 4:39 AM on December 30, 2008


By the way, Venus has been particularly bright recently in the southwest sky during the early evening,

On New Year's Eve, Venus will appear in the sky very close to the crescent moon.
posted by eriko at 5:50 AM on December 30, 2008


It sounds like if solar winds can remove water from Venus's surface wouldn't it remove everything else as well? Perhaps all the water is being evaporated during the day and staying in the atmosphere during the night. It's not like anyone has landed on the planet and saw that there is no water anywhere. Either that or it's underpants gnomes.
posted by Mastercheddaar at 6:15 AM on December 30, 2008


In any case, I don't think I understand the theory. If the solar wind is ripping apart water and blowing away the hydrogen and oxygen, why isn't it also ripping apart the carbon dioxide (which makes up 97% of the atmosphere) and blowing away the carbon and oxygen, leaving a bare rock?

Possibly because the bonds holding carbon to oxygen in carbon dioxide take 50% more energy than those of water to break?
posted by imh at 6:42 AM on December 30, 2008


On New Year's Eve, Venus will appear in the sky very close to the crescent moon.

This should be a link. I mean, there ought to be a site that can handle star charts the way Google handles maps.

Please... somebody... where is this site?

I use Stellarium, which is excellent and free. But where is the web-based equivalent?
posted by twoleftfeet at 6:44 AM on December 30, 2008 [1 favorite]


...the bonds holding carbon to oxygen in carbon dioxide take 50% more energy...

The solar wind is pretty high energy, IIRC. But maybe.

...there ought to be a site that can handle star charts the way Google handles maps...

Ironically, Google Sky doesn't really do this. The JPL Solar System Simulator will kind of do it.
posted by DU at 6:59 AM on December 30, 2008


Whoops, JPL Solar System Simulator.
posted by DU at 7:00 AM on December 30, 2008


Ironically, Google Sky doesn't really do this.

First, thanks for alerting me to Google Sky (somehow I missed that). Second, they are definitely screwing up by not integrating it correctly with Google Maps. I should be able to type my home address into Google Maps, get a map and a satellite view, then I should be able to pan upwards from Street View to get a picture of the sky above my house.

This is a no-brainer, right?

If only Google was as smart as Metafilter...
posted by twoleftfeet at 7:27 AM on December 30, 2008 [1 favorite]


Neat post- thanks!
posted by small_ruminant at 9:24 AM on December 30, 2008


I also don't really understand this. If they're detecting elemental H and O (presumably in the form of H2 and O2 gas, but that's not clear), why do they assume it came originally from water molecules? Why not just hydrogen and oxygen gas in the atmosphere? (Maybe the 2:1 ratio just doesn't match the bulk composition of the atmosphere, to propose an answer to my own question.)

Also, why would water need to be broken apart to fly in the solar wind? Why couldn't it fly as water? Or maybe their instruments can't see the difference between water molecules and a mixture of H2 and O2 gas in the right stoichiometric ratio?

Neat post, but it leaves me wanting more!
posted by Quietgal at 10:43 AM on December 30, 2008


Chuck Norris drank it all
posted by kcds at 11:10 AM on December 30, 2008


Venus and Mars have insignificant magnetic fields because their cores aren't still spinning because they did not have massive collissions forming essentially a double planet system like the earth moon system.

As per the articles in the original post, Earth's magnetic field prevents some of the ionizing radiation from splitting large molecules in the upper atmosphere.

When large molecules are split, the lighter ions or molecules, H+, H2, He leave the rocky planets because their velocity exceeds the escape velocity of those planets. Heavier molecules O2 etc have speeds less than the escape velocity and remain.

Mars, like Venus is hydrogen poor. The excess Oxygen on Venus seems to be bound to Carbon, while the excess Oxygen on Mars seems to be bound up in carbon dioxide, peroxide and perchlorate which would make Mars very inhospitable to us.

I've always discounted loss of hydrogen in a hydrogen based economy as something which would be inconsequential, until I read that ESA article in the original post ( 2x10^24 hydrogen nuclei a second (~ 3 grams/second ) lost) and that little amount over a lot of time adds up to a world without water.

But the "long" time required makes it a non issue on earth even with a greater los rate. Given that a hydrogen economy would experience a lot more than 3 grams a second loss (I figure 10^6 g/s) due to spillage and incomplete combustion we'd still take about 10^5 years to affect the hydrosphere by 1 part per million which well, is a negligible change in H+.
posted by ecco at 11:34 AM on December 30, 2008 [2 favorites]


...their cores aren't still spinning because they did not have massive collissions...

I didn't know that the massive collision was what set the core spinning. Is this a Known Thing or "just" a theory? If true, it's a major blow, if you will, to the "life everywhere" idea. All the goldilocks stuff has to be right PLUS a massive collision that hasn't completely died away yet.
posted by DU at 12:02 PM on December 30, 2008


"The giant impact hypothesis is the now-dominant scientific hypothesis for the formation of the Moon". So ETs require all the goldilocks stuff (distance from star, right type of star), and a large moon for a stable tilt, a strong magnetic field and a place for all the regolith (useless rock) leaving a heck of a lot of metals close to the surface. (The ET angle is what is explored in the book I linked to in my previous post, "Rare Earth: Why Complex Life is Uncommon in the Universe", the rebuttal book "Where is everybody? Fifty solutions to the Fermi paradox and the problem of extraterrestrial life" is well written but didn't convince me. YMMV).

FWIW: I forgot to mention the obvious place Oxygen went to on Mars; rust.

The 10^6 g/s came from the following logic based upon crude oil consumption as a proxy for H2 in a hydrogen economy; (85,270,000 bbl/day * (1/(24*60*60)) day/second * 158.9873 L/bbl * (1/1000) m^3/L * 873 kg/m^3 * (1000 g/kg) ~ 10^8 g/second of oil consumed ). 1% arbitrarily chosen as loss rate due to spillage and incomplete combustion.

The speed of the average gaseous molecule can be found via equating average molecular thermal energy (3/2)kT with kinetic energy
(1/2)mv^2 yielding v=sqrt(3kT/m).
Where k is Boltzmann constant (1.38e-23 J/K), T is in Kelvin and m in kg.

O_2 has mass 2( 2.66e-26 kg) = 5.3e-26 kg.
H_2 has mass 2( 1.67e-27 kg) = 3.3e-27 kg.
Which comes from atomic weight / Avogadro's 6.022e23 = grams/molecule.

Say room temperature is 79F, 22C, 295K then O_2 is zipping around at
480m/s or 0.48 km/s (about 1000 miles an hour), similarly the average
H_2 molecule is going at 1.9 km/s (about 4300 miles an hour).

The escape velocity for Earth at ground level is 11.2 km/s and for Mars 5.0 km/s.

The fudge factors now start because at ground level at room temperature these molecules seem to be within the escape velocities, and should all remain, but empirically there isn't any free H2 in either atmosphere but there is free O2, so I just have to wave my hands a bit and say the "effective temperature" at the edge of the atmosphere is such that some have enough velocity others do not. I.e. The solar wind gives the molecules a bit of a kick and at the edge of the atmosphere the escape velocity is also a bit lower than that stated above which is for ground level.
posted by ecco at 5:23 PM on December 30, 2008


I didn't know that the massive collision was what set the core spinning.

"The giant impact hypothesis is the now-dominant scientific hypothesis for the formation of the Moon".

If this link was addressed to me, it doesn't answer my question, because it says nothing about spin.
posted by DU at 6:49 PM on December 30, 2008


Once upon a time, Amtorian oceans covered most of the planet.

Mysteries may be uncovered by science, but sometimes they're better left alone.
posted by cenoxo at 11:33 PM on December 30, 2008


Hi DU. I didn't directly mention spin. Thanks for pointing that out.

Well the earth once spun much more quickly, ("Regardless of the rotation and inclination the Earth had before the impact, after the impact it would have had a day some five hours long...") and the spin of the molten part causes the magnetic field, ("In the case of the Earth, the magnetic field is believed to be caused by the convection of molten iron, within the outer liquid core, along with a Coriolis effect caused by the overall planetary rotation").

So it is safe to say at one time earth likely had a significant magnetic field due to the moon's impact, but you caught me stretching a bit and assuming that it has continued to this day because of the moon.

Both Venus and Mars do not have large moons, both do not have significant magnetic fields. I think that's significant. It seems reasonable to believe the initial impact imparted quite a bit of energy and the continued tidal forces have kept the core molten. But it's beyond my expertise and the only proof I can find is this abstract which essentially says someone finally proved the inner core is spinning faster then the mantle, and we know the tidal forces with the moon are causing the earth (or at least its flexible mantle to slow) then this suggests "astronomical effects can influence geological phenomena".

Now the abstract doesn't specifically say the friction between the two masses (inner core and mantle) generate enough heat to keep the outer core molten, so I'm still stretching, but it seems reasonable to me (they're awfully heavy).

The above would explain Mars and Venus, if you assume Venus's lack of a field is because its core has cooled. But there are other theories for why Venus does not have a field. ".. it is possible that ... its core is not currently cooling, so that the entire liquid part of the core is at approximately the same temperature."

So for Venus, the "uniform temperature" theory would make a moon irrelevant. So until we get permanent seismographs on Venus, or some clever person calculates the heating due to tidal interaction then the moon's role is moot.
posted by ecco at 10:18 AM on December 31, 2008




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