Other than some list says so, what makes you think they are “top” universities for you? I am not denying that they are. They will all be VERY different experiences from one and other though. You should put a little more emphasis on what you want your collegiate experience to look like beyond specious rankings.
Not knowing any more than what you’ve said (and that you probably read and liked The Martian ), I’ll throw out a name that probably isn’t on your radar, but may be a fit once you do a little more soul searching…Cal Poly.
Not only do they have a completely separate Aerospace department that’s not a subset of ME, they offer concentrations in either aeronautics or astronautics. The latter is not common. Several NASA sites, including JPL, along with SpaceX are in their top 10 employers for AE grads. The interesting angle though is that they also have a very well respected Agriculture school. The engineering curricula are packed, so I’m not sure how you’d work in the Plant Science/Agronomy/Botany angle, maybe a CubeSat project (which was invented at CalPoly). All the resources you could possibly need though could be found there.
As for activities, love and do well in math and physics. The highest correlation to success in an engineering program is the level of math you achieved in HS and how well you did. Other that that, do what you like. Admissions can sniff through BS ECs.