Two separate studies are claiming that Earth's two most prominent
surface fluids, air and water, came not from within but from outer
space. I have my doubts about these studies' conclusions, it seems like
a stretch that there could be enough air and water brought from meteors
that are being randomly hurled toward the inner solar system, especially
when the vast majority of them are likely heading towards the Sun.

Yousuf Khan

Are Earth's Oceans Made Of Extraterrestrial Material?
"According to books, the ocean and the atmosphere were formed from
volcanic gases and the Earth's interior is the source of volatile
elements. However, the rocks of the Earth's mantle are deficient in
water (geochemists estimate its concentration at two hundredth percent).
The same is true on Earth's sister planets, Venus and Mars. The main
reason proposed by Albarède is that, during the formation of the Solar
System, the temperature never dropped sufficiently between the Sun and
the orbit of Jupiter for volatile elements to be able to condense with
planetary material. The arrival of water on Earth therefore corresponds
to a late episode of planetary accretion."
http://www.sciencedaily.com/releases...1111110045.htm

Earth's atmosphere came from outer space, scientists find
""We found a clear meteorite signature in volcanic gases," said Dr Greg
Holland the project's lead scientist.

"From that we now know that the volcanic gases could not have
contributed in any significant way to the Earth's atmosphere."
http://www.sciencedaily.com/releases...1210153538.htm