Mercury

There is no atmosphere. The core is molten from 1/3rd of the way in down to the centre.

The planet is tidally locked and rotates three times for each two orbits. One 88 day orbit is 88*2/3 = 58.6 day year. A hot day in sunlight is 700K, a cold night is 100K. The bottoms of polar craters are a constant night temperature, there is ice. The solar radiation density ("flux") is 7 times that on Earth.

Rockets get faster as they fall toward the sun when going from Earth to Mercury. The only way to slow down is to carry fuel for braking. Then you need more fuel to land the fridge from orbit. You don't need to slow into an orbit if you just aim at the planet and land. Orbiting gives you a big sideways speed which you need to get rid of before you touch the surface.

The surface is made of rocks. The surface would melt if heated more with concentrated sunlight or with electricity. Trapping gas needs cold. Electrolysis might separate the elements.

Propping one of the 1km mirrors near the surface would keep the day temperature down nearer the cold night temperature. There is no atmosphere to carry the heat into the shaded area. Blocking the view sideways would also reduce infrared heat radiating from the sunlit surface. Working in a trench above 70N or 70S will keep the nots cool all the time while allowing daytime power generation at the surface - that's what NASA proposed ten years ago in their shelved lander paper (a copy is on the forum). Keeping the bots out of the sunlight is probably a good idea.

How to soft land on Mercury

Nobody has yet, but they have on the moon.

• Luna 9 and 13 airbagged.
• Surveyor 1 fell 3.4m onto a crumple zone. Apollo used a contact probe and fell from 1.6m. Surveyor 3 was 292kg and 700kg fuel.

The direct approach velocity is perhaps 2km/s so that's the least speed you have to get rid of. There's no air no swerving no parachutes no heatshield.

The ground mission would fail if the communications channels with Earth all fail. We might prefer to leave several communications satellites in orbit but I think the price would rise. Direct radio from the surface will reach any 30m dish we might have access to.