- Difficult to observe
Being the innermost planet of the Solar System, it always appears too close to the Sun. While the golden time for astronomical observations is at night, Mercury sets and rises in the sky nearly together with the Sun.
- Hard to reach
Mercury is actually more difficult to reach. According to some estimates, it would take less energy to get to the dwarf planet Pluto than it takes to get to Mercury. The reason for that is Mercury’s closeness to the Sun. A spacecraft aiming to not only fly past Mercury while in orbit around the Sun but to enter into orbit around the planet directly, has to constantly brake against the gravitational pull of the star.
- Too hot to orbit up close
Not only is sunlight around Mercury about 10 times more intense than near Earth, the planet’s scorched surface also radiates heat back to space. As a result, MPO will have to endure temperatures of up to 450°C, hot enough to melt lead.
- Difficult to observe
It’s expensive and the conditions are harsh.
The daytime side gets hot enough that a rover would be difficult to operate for long. You’d also be getting big swings between daytime hot and nighttime cold, so thermal expansion would probably be annoying.
Then it’s unusually expensive because orbital mechanics make it very difficult to approach the sun. We’re currently all flying sideways with respect to the sun, so if you launch something, it just wants to continue that orbit. In order to get closer, you’d need to shed most of that momentum, which takes a whole bunch of energy since inertia in the vacuum of space just means everything keeps going forever.
Land the rover in the twilight, then have it drive ahead of the sunrise using solar power.
It is the most difficult planet to land upon, but a solar sail could aid in slowing down. Mercury would be excellent for mining and to deliver resources throughout the entire solar system.
The issue is less that it’s the hardest to land on and more that it’s the hardest to get to, to arrive at and orbit. It takes less fuel to get to Pluto than it does Mercury.
Solar sails negate the need for fuel.
Can a solar sail get something from Earth to Mercury?
As a matter of fact, yes! Tacking a sail side to side allows a sailboat to sail upwind in a zig zag pattern. With a solar sail, a spacecraft can tack away from the direction of orbit, slowing down to reduce its escape velocity, and allowing the Sun’s gravity to pull it closer. All using no fuel.
Veritaseum breaks down the principle. https://youtu.be/jyQwgBAaBag
Neat, thanks.
