Since SARS is DNA based, much like life on Earth, you can't really prove that it's terrestrial or not. It's merely a matter of belief. Especially if you believe in the spore theory.

The only way to PROVE that it might be extra-terrestrial would be to find more of it in space.

Personally, I'd prefer people focus on more worth space theories ... I'd like to be more public money put into space development, but not at the expense of reasonableness.

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Live long enough to see Space!

We can get to space as a species. The above link is information about life-extension (living longer) so that you can personally see a space-based civilization.

The MPrize (a prize to encourage life extension research now contains over 3 million dollars.