[djf]

My inclination on the "Sars from Mars" theory is to reject it, only because the sars virus is Earth DNA type material, and is closely related to other flu viruses.

Something that comes here that is truly extraterrestrial would probably have a genetic basis that was, at least to a molecular biologist, obviously non-earthly.

[Don Joe]

They may be mistaking earth-air-borne virus samples for something from space. It might be possible for them to get to very high altitudes, and get sucked up to the edge of space, and then, if the conditions are right, sent into space for a spell. With the extremely thin atmosphere (almost no air resistance), and the microscopic size (and comensurate weight) of the things, it probably wouldn't take much for them to get accelerated fast enough to go suborbital for a while.