I couldn't find a better place to ask this, but I figured this exchange would know about the problems associated with traveling through space.
My question is if nanobots could spread through the universe, by the same method some people think life got on Earth, by an asteroid or other chunk of matter containing bacteria.
If nanobots can be made to self replicate (and as far as I can tell there are no credible scientific arguments against the underlying theories laid out by Drexler, carbon atom moving arms have apparently been made as well as a variety of <100 atom motors) they could eventually reassemble all carbon on Earth into more nanobots. I don't care about precautions or self-assembling bots being "needlessly complex" as Drexler himself says, those do not stop malicious determined intent.
Assuming this happened, how likely is it that something could hit Earth with enough mass that chunks containing nanobots would fly off and land on some other planet? I don't know much about space, my knowledge is limited to the idea that black holes and stars might pose problems for them. But only one chunk or single nanobot really needs to collide with any carbon containing material in order for them to continue spreading. If its feasible enough with bacteria that Panspermia is an actual theory, I don't see why it wouldn't be much easier with much better "bacteria."
Is this a likely scenario, or are there realities about space that I am missing?
In response to first answer
GremlinWranger's answer provides some good points but there is one thing I wanted to clarify. A few of the points seem to be talking about a single nanobot, specifically when one lands on a speck of dirt and can't find essential materials.
A more likely scenario I believe is that a chunk of rock or ice with many bots in it hits the Earth and explodes, scattering bits in a large area. Now it is possible that none of those land on usable elements, but could forces on Earth not move them around? If they are solar powered, all that is required is for some animal or wind or bug to accidentally move them to a place where they have sunlight and carbon.
I think that the point about radiation might work. With the large distances of space and the abundance of radiation (to knowledge anyways), it does seem likely that some amount of radiation would hit the nanobots. I don't know enough about space to know if the particles/waves would hit all of them, but considering that humans need to be constantly repairing their cells, combined with potentially massive distances traveled, this might be a big enough problem to significantly decrease the chances of this being a real threat. This is assuming that the radiation in space could damage diamondoids, but my limited understanding of radiation is that the only way to survive it is to have a lot of mass in the way, or to repair the damage as it happens, both of which the nanobots would not have.
Unless they develop Strong AI which I personally think will be even harder to create than nanotechnology, radiation and a lack of significant energy sources in the middle of space will probably be the best defense against this possibility. Assuming of course that another problem doesn't prevent self-replicating nanobots from being created in the first place.