I agree, it is not off-topic. It is firmly within the scope of planetary science which we allow here. We get a lot of questions mistakenly asked here that belong at Astronomy, and this one happens to also be on topic there, so users sometimes err on the side of marking off topic too quickly. That said, there were some other points raised in the comments to ...
I would run if and only if nobody better placed does.
My activity on Space Exploration has been moderate, but I am an active moderator over at Earth Science Stack Exchange, which has some overlap with Space Exploration (my day-to-day-work is with weather satellites, which involve both Space Exploration and Earth Science).
Site stats as of today:
90% is probably in the "typical" or "normal" or "healthy" range for a Stack Exchange site.
The statistics cited in @called2voyage's comments below the question further indicate that the unanswered 10% is somewhat explainable; ...
We get those because Stack Overflow Blog is one of our feeds. Since that is the official Stack Exchange blog, we have it as a feed so that we can quickly see any SE updates. The blog also happens to have a lot of material geared toward Stack Overflow specifically, but we can't tailor which posts we get from the feed except by deleting them from the chat room ...