If I use this on a planet with no research, will it make it Extremely Sparse or not work at all?

It should make it Extremely Sparse but why would you want to use it on a world like that?? Why not up one of your already made research worlds??

More curiosity than anything else. I can see there being a time when it could be handy info (if somehow you'd maxed out all your good planets on research already).

lol If that where the case than you need to go on a scan blitz and get more worlds or wait till you get a starchart and use that. I would never use a planetary Data Opitmizer on a world that was not a research world to start with. The thing I could see this post helping with is that the terraformers would do the same thing. If you would use a terraformer on a world that had resources like this:

Mining: rich
Artifact: Abundant
Research: none

It would turn to this:

Mining: very rich
Artifact: Very Abundant
Research: very sparse

I can see a time when I have a good planet with great mining and great artifacts but no research (say a maxed out very large+ toxic). I might already have a warp gate, a Relay Tower, Refining Lab, 2 Spy Uplink (for cloaking purposes), etc on the planet. It's probably already being defended if it is that good so bumping up the research just gives the planet a bonus. Worth doing, probably not but it doesn't hurt to know you can do it!

As for me, my data optimizers so far have gone into the crappy v. massive gas planets I grabbed up when I was an inexperienced newbie to the game. This reduces the sting of having such worlds by quite a bit, and ensures that my production is nicely spread out over multiple planets. After all, the most important factor in determining how much extra production from your optimizer is not which planet is already at a high prod% but what the base production is.

Well in that sense, you actually get the most from the largest planets, a huge gas planet is a good target for it. +25% has nothing to do with the existing quality and everything to do with the research building capacity that can be put there. Of course, if it's not the primary stat or close to it you're not going to do research on it anyway, so the above is still true (in general planet is already a research world).

Yeah, using those on Gas Planets is definitely a great idea, you get the most out of it and can make them very useful.

Plus you get up to 350 attack from Gas Igniter Rod without taking up any space.