by Ann » Sat Dec 05, 2015 6:33 am
Alohascopa wrote:
Any ideas on where the water so abundant in the 'snow side' of the solar system came from? And where the waters in comets and asteroids came from?
Well, like bystander said, there clearly was a lot of hydrogen and oxygen in the early solar system, which easily combined into water. But now consider the snowline. On the warm side of the snowline, water is a gas. That is because it is too warm there in the protoplanetary disk for the water to be a solid (and if it is a solid, it is ice), and it can't be a liquid there, because the ambient pressure is too low. Think of it. Water is liquid on the Earth not only because Earth is the right temperature, but also because we have an atmosphere that creates just the right atmospheric pressure to force water to be liquid here.
This youtube video explains that water boils at a lower and lower temperature as you get higher and higher up on Mount Everest, and the atmospheric pressure around you keeps dropping:
Click to play embedded YouTube video.
There might have been some "atmospheric pressure" in the protoplanetay disk that the Earth formed from, so there might have droplets of water there, for all I know. But mostly, the water there was gaseous. Beyond the snow line, the water was solid. It was ice.
I once listened to an astronomer who said that making planets or moons on the cold side of the snowline is like making a snowball. You just scope up the snow and ice and compress it, along with some pebbles and gravel that happen to be mixed with the snow.
But you can't make a "liquid water ball" or a "water vapor ball" by trying to scope up water vapor and compress it. You can just grab a handful of pebbles, and the water you get is the water that might be incorporated inside the pebbles. And we really know that the pebbles in the protoplanetary disk did contain some water.
But most of the water on the warm side of the snowline probably never got incorporated in any planets at all. It just kept floating around there in molecular form in orbit around the Sun. In contrast, most of the water on the cold side of the snow line grew into large "snowballs" and turned into planets and moons, comets and asteroids. (So what happened to the asteroids that robbed them of most of their water? Well... I read about a hypothesis that there might have been a large shakeup in the early solar system, where Jupiter and Saturn first moved closer to the Sun and then turned back again. Maybe Jupiter pushed the proto-asteroids in front of it, and their ice melted and their water evaporated, and then the asteroids as we know them today formed out of those desiccated rocks... I haven't got the faintest idea.)
Ann
[quote]Alohascopa wrote:
Any ideas on where the water so abundant in the 'snow side' of the solar system came from? And where the waters in comets and asteroids came from?[/quote]
Well, like bystander said, there clearly was a lot of hydrogen and oxygen in the early solar system, which easily combined into water. But now consider the snowline. On the warm side of the snowline, water is a gas. That is because it is too warm there in the protoplanetary disk for the water to be a solid (and if it is a solid, it is ice), and it can't be a liquid there, because the ambient pressure is too low. Think of it. Water is liquid on the Earth not only because Earth is the right temperature, but also because we have an atmosphere that creates just the right atmospheric pressure to force water to be liquid here.
This youtube video explains that water boils at a lower and lower temperature as you get higher and higher up on Mount Everest, and the atmospheric pressure around you keeps dropping:
[youtube]https://www.youtube.com/watch?v=8lyqFkFsH28[/youtube]
There might have been some "atmospheric pressure" in the protoplanetay disk that the Earth formed from, so there might have droplets of water there, for all I know. But mostly, the water there was gaseous. Beyond the snow line, the water was solid. It was ice.
[float=left][img2]http://pad1.whstatic.com/images/thumb/f/f8/Make-a-Snowball-Step-2.jpg/670px-Make-a-Snowball-Step-2.jpg[/img2][/float] I once listened to an astronomer who said that making planets or moons on the cold side of the snowline is like making a snowball. You just scope up the snow and ice and compress it, along with some pebbles and gravel that happen to be mixed with the snow.
But you can't make a "liquid water ball" or a "water vapor ball" by trying to scope up water vapor and compress it. You can just grab a handful of pebbles, and the water you get is the water that might be incorporated inside the pebbles. And we really know that the pebbles in the protoplanetary disk did contain some water.
But most of the water on the warm side of the snowline probably never got incorporated in any planets at all. It just kept floating around there in molecular form in orbit around the Sun. In contrast, most of the water on the cold side of the snow line grew into large "snowballs" and turned into planets and moons, comets and asteroids. (So what happened to the asteroids that robbed them of most of their water? Well... I read about a hypothesis that there might have been a large shakeup in the early solar system, where Jupiter and Saturn first moved closer to the Sun and then turned back again. Maybe Jupiter pushed the proto-asteroids in front of it, and their ice melted and their water evaporated, and then the asteroids as we know them today formed out of those desiccated rocks... I haven't got the faintest idea.) :wink:
Ann