Astronomers Finally Find The Answer To Earth's Water Mystery

Looking at her picture, you may think that Earth is a water world. But the fact is that she is 99 per cent dry rock. According to our current solar system formation model, this is impossible — a mystery that has puzzled scientists until now.

Rebecca Martin and Mario Livio of the Space Telescope Science Institute in Baltimore, Maryland, may have found the solution to this riddle using data from the Hubble Space Telescope. By observing how young stars behave, they came up with a new model that may forever change our understanding on how planets are created.

The Old Model

In the original theory, called the standard accretion-disk model, the planets in our solar system formed from a disk of gas and dust around the sun billions of years ago. Gravitational forces caused this disk, called the protoplanetary disk, to condense in different lumps that eventually formed the planets we know today.

Depending on their distance to the sun, the planets had different characteristics. According to the standard model, any planets that fell within a certain zone would be dry and rocky. Any other planet outside that frontier would be ice water worlds. This frontier — called the snow line — left Earth well into the ice area. According to Martin:

If the snow line was inside Earth's orbit when our planet formed, then it should have been an icy body. Planets such as Uranus and Neptune that formed beyond the snow line are composed of tens of percents of water. But Earth doesn't have much water, and that has always been a puzzle.

Only 0.02 per cent of Earth's volume is water. According to current theories, that water may even come from the asteroids and comets that bombarded Earth after its formation. How is this possible?

The New Model

The answer seems quite simple. Martin and Livio found a problem in the old model: It didn't take into account the fact that "disks around young stars are not fully ionised".

We said, wait a second, disks around young stars are not fully ionized. They're not standard disks because there just isn't enough heat and radiation to ionize the disk. Very hot objects such as white dwarfs and X-ray sources release enough energy to ionize their accretion disks, but young stars don't have enough radiation or enough infalling material to provide the necessary energetic punch to ionize the disks.

They concluded that the snow line in the old solar system model was not in the right place. Since there was no ionisation in the disk, the matter wouldn't move in the way that the old model accounts for. In fact, there would be many other areas. In the centre there would be a turbulent region, very near the sun. Surrounding that there would be an icy dead zone, which would block any matter from falling into the sun.

A third area, called the self-gravitating warm dry region. Here, gravitational forces heat up the dense matter floating in the disk. This causes any ice to vaporise. It is in this area where Earth formed. According to Livio, while this is not a blueprint for all disks, since there's a chance element that may affect the formation of a planet like Earth. Their new model, however, explains all the planets in our solar system accurately:

Unlike the standard accretion-disk model, the snow line in our analysis never migrates inside Earth's orbit. Instead, it remains farther from the Sun than the orbit of Earth, which explains why our Earth is a dry planet. In fact, our model predicts that the other innermost planets, Mercury, Venus, and Mars, are also relatively dry.

[Hubblesite and Gizmodo]


Comments

    I really wish I studied more at school .... fascinating !

    The old model never made any sense and rightly so when you compare the it to the new model. Funny how a simple chang in view elevates our understanding. In this case it's a change in assumptions made years ago that we clearly know to be false now.

      yay Community!

        He is very simple and a little psychotic.

        you are talking about jesus right?

      I think its more accurate to say *what we think we know now*

    What about how planets are formed from the God Particle theory!!

    I guess I didn't read both these articles in detail :(

    So if water on earth came from Asteroids, Water on Mars would also likely have come from asteroids. Therefore we shouldn't be surprised that Mars has water. Rather we should be surprised if Mars has no water.
    Therefore all the kerfuffle about finding water on Mars is just an attention grabber!

      The standard belief is that Mars had an atmosphere and water on the planet (the deep grooves suggest it had huge glaciers). The theory goes that Mars has a low magnetic field, (the very thing that protects Earth against solar winds vaporising our atmosphere) and at some point the atmosphere was vaporised by major Solar winds bombarding it. The only water left on Mars is likely to be water crystals frozen under the surface.

      On the water found on Earth scenario, it is still a strong belief that an asteroid made of ice particles collided with Earth, giving us the oceans we have today and because of its high mineral salt content, its more likely to come from somewhere other than Earth.

    What's the connection between density, water states and distance from the centre of the disk?

    The shitty thing about this is that anyone with a rudimentary understanding of Astrogeology could have told you this.. but because there is no specific evidence to back it up, it's just "imagination" and nothing more..

    So it's not so much a matter of "finally finding the answer" as much as "finally PROVING the answer".. there's a big difference.

    maybe I'm crazy but the first thing I thought of when I saw the main image (earth with the water separate)

    http://www.lionheartradio.com/interviews/images/patrickmoore.jpg

    So if I understand correctly the new theory = the way it is now is different to the way it was previously (i.e. when the sun was young)? Admittedly I'm an outsider to the field but I'm frankly doumbfounded that this isn't a basic tenet to all theories in astronomy and cosmology.

    For all we know, there could originally have been 2 suns and the "hot turbulent region" extended out to Mars but then one of the suns wandered off or got absorbed in to the other which reduced the region, started global freezing, and killed off the dinosaurs.

    I don't know, I'm making stuff up, but I'm just saying that things change especially over the timescales that we are discussing.

    So where did the asteroids get all their water? Are we really solving a problem or just moving it to somewhere we can't test?

      The asteroid is made of water crystals and dust. Not a big rock with water on it.

    Chaos is simply the limit of our ability to understand everything that has happened upto the present.

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