Water Fact File for the Solar System

The Bottom Line:

Lots of water here...


Findings from Dr Kotwicki's 1991 Paper:

The Solar System, as usually defined, extends 6 x 109 km from the Sun to the orbit of its outermost known planet Pluto. Technically, the gravitational sphere of influence of the Sun reaches about halfway to the nearest star, some 2 x 1012 km, and changes in time as stars change their position. The Solar System is distinctively well defined - the distance to the nearest star exceeds 3000 times its diameter - but definitely not distinct: so far astronomers have found some 1011 galaxies similar more or less to our Milky Way Galaxy. There are on average 1011 stars in the galaxy and many of them may posses planets.

It is now usually accepted that members of the solar family assembled from the cold solid and gas particles of the spinning solar nebula in a relatively short time of 100 million years (Wetherill, 1980). They passed through periods of intensive bombardment, vertical differentiation of bigger bodies, outgassing, and other processes in the formation of what is presently  called the Solar System. A significant amount of primordial water might have been lost in this process: it is widely accepted  (Torbett (1989) that on the order of 90% of icy planetismals have been sufficiently gravitionally deflected by close  approaches to protoplanets to have been ejected from the Solar System into interstellar space. As these are unlikely to be seen again, let us make an inventory of the remainder.

Water in the Solar System

On our local (very local, indeed) scale, water appears to be in sufficient quantities to satisfy any conceivable needs of the present and future inhabitants of the Solar System. From the whole mass of this cosmic entity, 2 x 1033 g, of which 99.87% is concentrated in the Sun, the amount of water in planets, moons and comets at 1029 g is a formidable quantity, exceeding 20 times the mass of the Earth or some 100 000 times the mass of the World Ocean. Based on existing  knowledge, the ratio of the mass of the Sun to the mass of all other objects to the mass of water is of the order of  20 000:20:1. What should be remembered is that the present estimates of the mass of comets may be very conservative and that one day we may find that they outweigh the Sun.

Just for illustration and a homely comparison it can be visualised that water circulates in the Solar System in a manner,  which to some extend resembles our beloved Earth's hydrological cycle. One can imagine that water droplets (comets) form a cloud (Oort cloud) from which they fall to the centre of gravity if specific conditions are met. They can fall onto the Sun and evaporate, blown away by the solar wind back towards their place of rest. The cloud itself can lose or gain some comets from other stars or from molecular clouds through which our Sun passes. Comets falling towards the Sun can be  intercepted and find temporary storage on planets and their moons - however, they eventually evaporate back to the cloud. And then, a comet one day appears again.



Latest Findings about Water in the Solar System:



Above: The Solar System.

Water in the Universe
Water in the Universe

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