Is the Earth losing water into space?

Is the Earth leaking? Could water evaporate into space? Given enough time could the Earth end up like Mars: a desolate wasteland with not a drop of water to be found?
14 June 2009



I’ve always wondered, is the Earth leaking? Could water evaporate into space? Given enough time, could the Earth end up like Mars: a desolate wasteland with not a drop of water to be found?


We put this question to Luca Montabone, Atmospheric, Oceanic and Planetary Physics dept., Oxford University...

On the Earth, water can exist in all three forms namely as a solid, liquid, or gas. Evaporation transforms liquid water into water vapour which can then freely move in the atmosphere as a gas.

Now, atmospheric molecules, including water vapour molecules, are in perpetual motion in all directions. Without the gravitational field of the Earth, those moving away from the planet would be lost. Even with the gravitational field, in the upper thin part of the atmosphere, a molecule moving outwards has little chance of colliding with another and would therefore be able to escape if it has sufficient speed.

The average speed of the gas, for example water vapour, depends on its temperature. The conditions of temperature at the altitude from which water molecules are able to escape indicate the earth can retain water vapour over geological time scales, that is, over several billion years.

The retention of water vapour on our planet is also favoured by the fact that it can condense, form clouds at an altitude well below the one from which water molecules can escape and precipitate back to the ground as rain or snow.

Adding to all these, we have to remember that water is also introduced in the hydrological cycle from the interior of the planet, for example, every time that a volcanic eruption occurs.

So, to summarize, even if a few water molecules are continuously lost to space, the average level remains fairly constant over geological times, which is what we want!


Doesn't it seem like a good idea to study how a denser Troposphere will force lighter molecules into the higher atmospheres, therefore off-gasing a greater volume of lighter molecules into outer space?

There is water on Mars crust too, but not enough to survive.

Mars has got tonnes of the stuff within the crust material...

If water leaked from planets there would be water everywhere in space.... any sign of that?

Another site had an article on this subject once. It stated that water in the upper atmosphere is carried away by solar wind in the amounts of over thousands of gallons...

If the earth's gravitational force is what holds water in, then the earth had to be completely formed already, before water could be introduced. It could not have been formed with other elements of the planet because it would have evaporated into outer space before a mass formed that revolved and rotated around the sun which cause the gravity. So how do you explain water's existence at all?

Most of the water on the planet arrived after Earth first formed in the form of comets and asteroids.

we know rotations and revelutions helps in carry gases on the earth surface which we called as atmospheric gases. once a gas is escaped from the planet it will stay in space as the pressure of the gas will be low as it's the only gas in that particular place of space. if it is compound of gases also one gas will stay above or below the other gas. if te pressure the gas increases also it either have to move away from the sun but doesn't come closer to the sun. and there's a chance of carrying that gas by other planet when it comes to that point. but coming to that orbital path for a planet is not possible, so once earth comes back to the same place it may carry back those gases. so there's a chance of retaining water molecules on to the earth surface. it's just my assumption. if anyone know very well 'bout this topic can still answer to these question.

So common when reviewing the literature above, science seems to be claiming that every time a certain amount of water vapour escapes into space, that much water vapour comes back from the interior of the Earth, is that correct? If it is, show us your evidence.

The answer above does not state that water out = water in. It alludes to the fact that there is a lot of water bound up within the Earth's crust itself (in addition to what is in the oceans): recent studies suggest that 5-10 times the amount of water that is in the oceans is locked up within the top 500-1000 miles of crust. We know it's there because volcanologists have sampled volcanic ejecta, which are like the geological equivalent of doctor taking a tissue biopsy from deep within the planet.

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