Earth was probably formed in a hotter, drier part of the solar system than previously thought, which could explain our planet's puzzling shortage of water, a new study reports.
Rebecca Martin and Mario Livio of the Space Telescope Science Institute in Baltimore, Maryland, may have found the solution to this puzzle using data from the Hubble Space Telescope.
They observed how young stars behave and came up with a new model that may forever change our perception on how planets are formed.
The Original theory
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 as known today.
Depending on their distance to the sun, the planets had different characteristics. Any planet felling within a certain zone would be dry and rocky. Any other planet outside that frontier would be ice water worlds. This frontier is called the snow line and Earth fell 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.”
The Latest Theory
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.”
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 suggests.
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.