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.
The orbital mechanics thing is probably the most important. The delta-v to land isn’t that bad once you’re in orbit, but even getting to orbit is crazy. Also, you’d need a retro rocket for landing that could withstand the temperatures – which would be a super interesting engineering problem. It already is for the orbital probes, but they don’t have to carry enough fuel to land and have different mass budgets.
And it also might be kinda boring. I mean, they’re bound to find something, but it comes after after formerly-wet Mars and formerly-mysterious Venus, and from the fly-bys the surface looks a whole lot like the moon, which is right here.
The agencies talked about sending something there, but basically never got around to it.
No swings between day and night, mercury is tidal locked. So you could land on the hot side (+430°C) or on the cold side (-170°C), and it stays this way. Landing at the border between day and night is probably even more challenging.
Mercury actually isn’t tidally locked, it has a 3:2 resonance, so does have a day/night cycle.
TIL. Thanks.
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.
Mercury’s surface temperatures are both extremely hot and cold. Because the planet is so close to the Sun, day temperatures can reach highs of 800°F (430°C). Without an atmosphere to retain that heat at night, temperatures can dip as low as -290°F (-180°C).
I think this is the big reason. It’s also close to the sun, which makes it difficult to land something on it. There’s likely not as much value in doing it just yet, while we can gather data about its composition through other methods. Eventually we might do it, and I imagine it’ll be for resources of some kind
https://www.space.com/41664-mercury-lander-mission-study-proposal.html
I found this article just now but have read it all yet. Seems relevant
Mercury has been devoid of spacecraft companions since NASA’s Messenger mission ended in 2015, and while the next mission bound for the innermost planet launches later this year, it won’t arrive until 2025.
On the last point, here is that new mission and the updated timeline
https://en.m.wikipedia.org/wiki/BepiColombo
On 15 May 2024, ESA reported that a “glitch” prevented the spacecraft’s thrusters from operating at full power during a scheduled manoeuvre on 26 April.[9] On 2 September, ESA reported that to compensate for the reduced available thrust, a revised trajectory had been developed that would add 11 months to the cruise, delaying the expected arrival date from 5 December 2025 to November 2026
Never knew about that mission. Also to the point of OP’s topic, there was a lander planned but it got cut due to budget constraints. And probably because of the environment also mentioned by someone, it was only planned to operate a week.
A rover that could stay in the terminator region might survive longer, but that would likely have to be very automated since Mars rovers guided by humans aren’t necessarily that fast due to the time for communications.
This is just my guess, but I’d say it’s probably too expensive to get one there and it wouldn’t be worth it. There’s not a whole lot interesting to study on it. Funny enough, the surface of Venus (465°C) is hotter than the surface of Mercury (427°C), and we’ve visited and landed a probe (several, actually) there. They even took some pictures. Venus is a lot more interesting though. It has an atmosphere and weather. Mercury is just a barren rock.
- 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
Mercury is boring because anywhere you go in the Solar system, on average, Mercury is the closest planet.
