As I discussed previously, Venus and Mercury are not high on my list of exploration goals, in regards to the Outbound mission. It’s not that they aren’t ultimately important, it’s that they aren’t well suited to colonization. We’re all about that at Outbound, getting humanity off-Earth and spread about the Solar System. That is goal number one. There may be many intermediate steps that lead to that goal, but going closer to the Sun to visit places we can’t really live upon, those aren’t the first steps.
That said, of course we need to know about these extreme places to fully understand our system, and to prove out our technologies. In fact, that would be the major value of visit the two inner planets – it’s a qualification testing ground. As Sinatra may have crooned: “If we can make there, we can make it anywhere.”
For OPS.14, Mercury is a planet with a nearly tidally-locked orbit around the Sun, with a period of about 88 days, seeing three revolutions for every two trips around, or a day of about every 2 Mercurian years. That means for about every 90 Earth days one side gets baked while the other is frozen, slowly transitioning between the two extremes. It also has no real atmosphere, just a thin exosphere whose composition changes based on off-gassing of the planet and the composition of the solar wind, or the occasional meteor strike. All of this over a silicate-rich surface. We have silicates already on Earth and frankly everywhere in the Solar system. Boy, do we have silicates. So we have no compelling resource needs to be met there, especially with the amount of effort required to get to what is there.
So why go to Mercury? To stretch our abilities, to learn that much more about our star system in general, and then bring that knowledge and experience back to the more habitable missions in the Outbound set of goals.