>A blind study has a researcher doing something with a subject that is not aware of the study's true / detailled aim.
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>A double blind study has a researcher tasking another researcher to do something with a subject, with neither the subject nor the tasked researcher knowing what the study is actually about.

This is not correct and would violate principles of informed consent. A blind study is one in which the participant doesn't know if they are getting the the study drug (or procedure or whatever) or if they're getting a placebo. A double-blind study is one in which the participant and the tasked researcher both don't know whether the participant is getting the drug or the placebo. In all cases the participant must know what the purpose of the drug is and any negative effects taking it or not taking it may have.

We're now into the fourth decade of hundreds of millions of women taking the pill for 10-15 years (often with interruptions to have a baby) so if it had an effect on delaying menopause we'd already be seeing it.

In some Asian countries kids are taught that everyone can learn any amount of math just by putting in however much effort is required. And anyone can learn piano, basketball, etc. Natural talent helps by making it easier, but everyone can learn it; no one is incapable.

On the other hand for a competitive job OP would probably be better served by focusing their effort on things that are easier for them to be really, really good at. NASA isn't hiring satellite engineers to design educational programs or sweet talk congresscritters into more funding or etc.

It depends on the location of the research institution and the communities they’ve trying to recruit from. For example, when I worked in research, we were based at a VA hospital near but not in a large city. We didn't go into the city to recruit study participants because we were too far away for people to be willing to come. We recruited young people from the local community college, and senior citizens from the places you'd expect to find older folks: the senior center, churches, restaurants that had 4pm dinner specials, etc.

I wonder if the flip side of this (inhibiting this circuit when it's overactive) might be helpful for people with depression and similar conditions where inability to do motivated behavior is a problem.

My understanding is that the problem for Mars and Mercury was that they aren't massive enough to keep their cores hot, so as the cores cooled their planetary dynamos slowed and the magnetospheres dissipated.

At least as far as physics, cosmology, other space sciences, etc, are concerned, if the answer to "can we do science about it?" is No, then ... yeah. By definition the question cannot be answered by science so science isn't going to worry about it.

If Io had been Juno's target, they would probably have calculated its trajectory and fuel needs to achieve either an actual orbit around Io or, if that wasn't possible, a closer flyby. But Juno's main target was Jupiter itself, so all photos of Jupiter's satellites were taken from the most fuel-efficient orbit around Jupiter.

The chances that you personally will be hit and killed by a meteorite? Effectively zero. Significantly smaller than your chance of being eaten by a shark while being struck by lightning.
The chances that a world-destroying asteroid will hit the Earth without warning are also effectively zero. NASA tracks all the medium-sized and larger asteroids that will, have, or may cross or approach Earth's orbit, and none (total zero) of the ones big enough to destroy a large area like a city are likely to hit us in the lifetime of anyone now alive.

Before you join the military, and while you're in if they'll let you (in the US they often pay for members to take graduate degrees), and afterward as necessary, take as much science and/or engineering as you can. Try to get at least one post-graduate degree in a field related to something you would do in space, whether a practical degree such as medicine or engineering, or a science like biology or chemistry. Two is better, but regardless pick stuff you like because you need to get top marks.

>What is its function?

Like a housecat, it doesn't have one. It's just here. What are you here for? There is no single answer to that question. You are free to choose the one you think is best.

Someday probably, but we currently don't understand the functional properties of unaffected brains well enough to reliably determine by a scan alone what is or isn't within the range of normal variation.

Additionally, these scans would be done by a functional MRI machine (basically a recording of brain activity; a regular MRI is more like a soft-tissue XRAY). Unfortunately fMRI machines with high enough resolution to see that kind of detail are few and far between, and fantastically expensive, so that's not a diagnostic route that will be available to most people.

Natural satellites, in contrast, do crash into each other. This is (probably) how several moons & moonlets in the solar system were formed.