With multiple rovers currently scurrying around on the surface of Mars to continue a decades-long legacy, it can be easy to forget sometimes that repeating this feat on other planets that aren’t Earth or Mars isn’t quite as straightforward. In the case of Earth’s twin – Venus – the surface conditions are too extreme to consider such a mission. Yet Mercury might be a plausible target for a rover, according to a study by [M. Murillo] and [P. G. Lucey], via Universe Today’s coverage.
The advantages of putting a rover’s wheels on a planet’s surface are obvious, as it allows for direct sampling of geological and other features unlike an orbiting or passing space probe. To make this work on Mercury as in some ways a slightly larger version of Earth’s moon that’s been placed right next door to the Sun is challenging to say the least.
With no atmosphere it’s exposed to some of the worst that the Sun can throw at it, but it does have a magnetic field at 1.1% of Earth’s strength to take some of the edge off ionizing radiation. This just leaves a rover to deal with still very high ionizing radiation levels and extreme temperature swings that at the equator range between −173 °C and 427 °C, with an 88 Earth day day/night cycle. This compares to the constant mean temperature on Venus of 464 °C.
To deal with these extreme conditions, the researchers propose that a rover might be able to thrive if it sticks to the terminator, being the transition between day and night. To survive, the rover would need to be able to gather enough solar power – if solar-powered – due to the Sun being very low in the sky. It would also need to keep up with the terminator velocity being at least 4.25 km/h, as being caught on either the day or night side of Mercury would mean a certain demise. This would leave little time for casual exploration as on Mars, and require a high level of autonomy akin to what is being pioneered today with the Martian rovers.
Top image: the planet Mercury with its magnetic field. (Credit: A loose necktie, Wikimedia)
The terminator speed is considerably slower at higher latitudes so the poles might the easist place to start. (And they have ice.)
but if you lose the Terminator, you can be sure that it will be back
If you can survive the cold, that might be a viable strategy. You’d have to build a ridiculous-looking rover, it would pretty much look like a turtle. Have an outer shell of the highest-specific-heat material you can get access to, ideally water from either mercurian ice or combining h2+o2. (Hydrogen itself has a pretty high specific heat but I don’t know if it’d be practical.) If you insulate your water-holding-tank shell well enough, you MIGHT be able to spend all your solar power heating water while in sunlight and retract into the shell like a turtle when the shade hits. The benefit of this approach is that it wouldn’t use power while retracted, unlike other solutions. An even stranger idea would be to store flammable gases, ideally replenished by electrolysis of mercurian ice, then run a gas heater while in night. It’s a mechanically simple system with few parts and low energy requirements. If you combine it with the water idea, you could have a catalytic heater that produces a small amount of heat to slow the temperature change during night, possibly lasting long enough to reenter the sunlight. An additional benefit of water is the phase change from water to ice, taking additional energy to freeze. Another idea, there’s a paint/film/fabric called Radi-cool that is able to keep objects relatively cool in direct sunlight by being black in the IR spectrum and white in the visual spectrum, reflecting light while still losing heat to thermal radiation. That would be useful in the day side, but what would be very interesting is making a material that is white in the IR spectrum and black in others. I don’t know how much light is available if any during night on mercury but this would at least help stay warm during twilight conditions and lower the demand on the electrical and/or gas heaters. If you use that idea, then instead of a turtle shell you could have a self-deploying tent for night/day time. You could either make the inside of the tent reflect heat with a silvery coating or make the tent reversible by having one side for day and one for night.
Why not use an RTG for power and heat?
Though It will keep get older with each new sighting…
I wonder what other plentiful emissions coming from the sun than a usual solar cell on Earth might generate even more power.
So basically, every sci-fi movie where the aliens would move to one planet and consume all its resources and then move onto the next planet werer really talking about us.
I mean… yeah, that wasn’t the point of the sci-fi stories, but most hostile aliens like that were thought of by looking at human behavior and human understanding of evolutionary pressures and then extrapolating out. Sometimes they’re just humanoids who are slightly further along in their civilizational development than humanity
I’m glad they at least acknowledged the preceding sci-fi sources of the idea. Kim Stanley Robinson’s 2312 came immediately to mind, and I admit I had not heard of Charles Stross’ take on it.
Somehow it feels not very likely to make a rover that travels the same distance every hour that the best mars rover did in 6 years.
Nearer the poles the absolute speed needed is much more manageable.
The temperature variation also ends up being smaller.
A burrowing “rover” seems like a fun idea.
The article doesn’t mention the gravity issue. It’s so close to the sun that closing that distance between us and it usually results in a huge delta V to overcome for a soft landing.
Yeah, gravity issue and speed made it into the (opening) remarks in Fraser’s presentation of the topic though (at 13:34): https://www.youtube.com/watch?v=TV_kJYQctvk&t=1123s
But don’t make the rover hide in the regolith, drop a lander pod in a crater that is subsequently covered with a thick layer of regolith.
The primary function of that pod would be its walls – not just to act as an underground shelter, but as a large area heat exchanger with a high temperature collector protruding from the mound of regolith.
With that, it’d be both possible to transfer a controlled amount of heat into the ground below and regolith cover mass above to recharge as a thermal battery for the Mercurian night, but perhaps also to run a Stirling engine, however small it will be.
The pod would have a hatch so the “crepuscular” rover could egress and do exploration runs, allowing missions to run over years.
Based upon the paper:
I’m thinking of a Mercury terminator following rover at 75 degree latitude.
Grok 3 AI:
I’m thinking of a Mercury terminator following rover at 75 degree latitude.
Grok 3 AI:
Yes, a Mercury terminator-following rover at 75° latitude is an intriguing and feasible idea that aligns closely with recent conceptual studies (presented at the 2025 and 2026 Lunar and Planetary Science Conferences by researchers from the University of Hawai’i at Mānoa). The core concept—staying in the narrow “twilight” band around the day-night boundary (terminator)—avoids Mercury’s brutal extremes: dayside temperatures up to ~427°C (800°F) and nightside lows to ~-173°C (-280°F). In the terminator zone, conditions stay relatively temperate (roughly -50°C to +50°C range, depending on exact position, terrain, and thermal inertia), with enough low-angle sunlight for solar power.
Terminator Speed at 75° Latitude
Mercury’s slow rotation (3:2 spin-orbit resonance) combined with its eccentric orbit makes the terminator sweep across the surface at varying speeds. The velocity scales with the cosine of latitude:
At the equator: ~6 km/h (3.7 mph) maximum.
At 45° N/S: ~4.25 km/h (2.64 mph).
At higher latitudes like 75°, the speed is even slower—roughly 1.55 km/h (about 0.96 mph), calculated via the cosine factor (cos(75°) ≈ 0.259) applied to the equatorial value. (Exact instantaneous speed varies slightly due to orbital eccentricity and can be refined with NASA JPL Horizons ephemeris data.)
The rover wouldn’t need to match the terminator’s speed exactly. It only needs to move fast enough to stay within a defined “temperate band” of longitudes (width depends on surface thermal properties, rover power needs, and how much temperature swing the design can tolerate). This makes higher latitudes easier: slower required speeds, smaller daily temperature variations, and access to scientifically interesting polar terrain (e.g., water ice in permanently shadowed craters).
Recent concepts even suggest starting at a polar or high-latitude landing site during a “lull” in terminator motion for initial acclimation and testing, then snaking or progressing along the terminator (possibly oscillating in latitude) toward lower latitudes for broader exploration.
Comparison to Mars Rovers and Feasibility for Faster Mobility
Current Mars rovers (e.g., Perseverance) average ~0.1 km/h due to safety, autonomy limits, rough terrain, and science stop-and-go operations. A Mercury terminator rover would require sustained average speeds of 1–6 km/h (depending on latitude)—much faster than Mars rovers but well within demonstrated capabilities:
Lunokhod 2: up to ~2 km/h.
The required speeds are achievable with better gearing, improved wheels/suspension for Mercury’s regolith, and advanced autonomy for continuous hazard avoidance while “running with the Sun.”
At 75° latitude, the ~1.55 km/h requirement is particularly manageable—closer to Lunokhod speeds and far less demanding than equatorial operations. Challenges like low gravity (0.38g), sharp regolith, and radiation exist, but the slower polar terminator motion reduces dynamic stresses compared to faster equatorial driving. High autonomy (real-time pathfinding) would be critical, as Earth communication delays make remote piloting impossible for sustained motion.
Thermal and Power Advantages (vs. Venus or Full Dayside Mercury)
Unlike Venus (where high-temp SiC electronics are essential for ~460–500°C survival), the terminator zone avoids the need for extreme high-temperature electronics. Passive thermal management, moderate solar arrays (optimized for low Sun angles), and modest energy storage for brief interruptions could suffice. This is a huge simplification compared to stationary landers or full dayside missions, which face melting or freezing issues. Near the poles, even milder swings help.
Scientific Payoff at High Latitudes
A 75° latitude terminator path would enable unique in-situ science impossible from orbit (MESSENGER/BepiColombo data):
– Sampling water ice and volatiles in polar craters.
– Studying hollows, volcanic deposits, tectonic features, fresh craters, and space-weathered materials.
– Instruments like LIBS, spectrometers, and possibly ground-penetrating radar could analyze composition and history across diverse terrains while the rover “creeps” along the twilight zone.
Traversability would use MESSENGER imagery and altimetry to plan routes avoiding steep slopes or obstacles.
Challenges Specific to This Design
Solar power at low angles — Panels must tilt or track effectively; batteries or capacitors for any shading.
Autonomy and navigation — Must maintain terminator position while avoiding hazards at sustained speeds.
Radiation and dust — Mercury’s proximity to the Sun means high ionizing radiation; regolith is abrasive.
Landing and deployment — High-latitude sites add orbital mechanics complexity, but a polar start during a slow period helps.
Mission duration — Could last many Mercury solar days (each ~176 Earth days) by staying in the band, far longer than a static lander.
Overall, your 75° latitude idea is smart: slower speeds, milder thermal environment, and high science value (ice + geology). It builds on the “Run with the Sun” and “Sun Run Relay” concepts, showing the terminator rover is within near-term tech—especially at higher latitudes.
Please stop posting lengthy AI-generated drivel.
Indeed – take a 4×4 to the middle of nowhere and try to drive in any given direction at a constant 5km/h no matter what, sooner or later you’re going to find yourself in real trouble one way or another.
This reminds me of the plan for airships on Venus, apparently there’s a layer that sits at about room temperature. It’s a shame Mercury has such a thin atmosphere. I do wonder what sort of vehicle design they might try for Mercury. Perhaps something akin to an inflatable ball with a rover inside. Something like the “fighting” robot Psychosprout, perhaps with ports to enable direct sampling. If large enough, it could roll over rough terrain with enough speed or even use it’s shell as insulation, with a TEG inside, huddling down for the brief winter freeze each day and just roaming in short hops as far into the night side as it could, only really needing to avoid the heat, rather than both.
Venus ROVER design concepts also fascinate me along with work on extreme heat tolerant electronics that could be used on one. One of many papers on that:
A Brief Overview of High Temperature Technologies for Venus Surface Applications
https://www.kiss.caltech.edu/workshops/VenusInSitu/lectures/hunter.pdf
Of course, what uses on Earth would there be for extreme temperature electronics? /sarc I’d rather have passengers floating around on TV in their $4.1 BILLION (according to NASA OIG) dollar mission to beat China to the moon… again.
We finally have a computer that can survive the surface of Venus
Sulphuric rain? Easy. Not burning up at 500°C or crushed by 90 atmospheres? Hard.
Feb 8, 2017
https://arstechnica.com/science/2017/02/venus-computer-chip/
A truly clever approach to survival on a harsh planet, though it seems like a tall order to expect an obstacle-free path for the rover’s “ground level orbits.” I’d bet there are some gas giant’s moons that would be of greater interest to resource limited space agencies, like Titan, Europa, or Enceladus. How about an alien moon undersea probe for a good challenge?
Check out the development in progress Dragonfly mission, a giant, nuclear powered quadcopter mission to Titan:
https://dragonfly.jhuapl.edu/index.php
More fascinating stuff going on. Ask Grok about things I know are happening:
Are there any proposals for small vehicle swarms on other planets and moons?
Are there any plans for probes melting through the ice to reach subsurface oceans on ice moons?
Link to Venus rover and high temperature electronics topics.
I knew there are. Just wanted specifics.
Are there any plans for probes melting through the ice on ice moons to reach subsurface oceans?
Grok 3 AI:
Yes, there are several active research efforts, technology development projects, and mission concepts focused on cryobots (ice-melting probes) or similar penetrators designed to melt through the icy shells of ocean worlds like Jupiter’s Europa and Saturn’s Enceladus to access their subsurface oceans. These concepts aim to search for signs of life in potentially habitable environments, building on data from missions like NASA’s Europa Clipper (which arrived in the Jupiter system after its 2024 launch) and ESA’s JUICE (en route, arriving 2031).
What Are Cryobots?
A cryobot is typically a cylindrical, self-contained probe that uses heat (from radioisotope power sources like plutonium-238 RTGs, small fission reactors, lasers, or hybrid electro-mechanical systems) to melt ice ahead of it. Gravity pulls it downward as meltwater flows around the probe and refreezes behind it, creating a sealed borehole. This avoids the need for complex mechanical drilling while minimizing contamination risks. Challenges include extreme cold (near 100 K on the surface), thick ice shells (estimated 10–40 km on Europa), power demands, communication through ice, navigation around obstacles (e.g., rocky debris), and ensuring the probe doesn’t get stuck.
Key NASA Concepts and Developments
PRIME (Probe using Radioisotopes for Icy Moons Exploration): A JPL-led cryobot concept that uses radioisotope heat to melt through ice. It could carry or deploy smaller submersibles or swarms of robots into the ocean. Related work includes modeling descent times (potentially months to years depending on power and ice thickness) and field tests.
SWIM (Sensing With Independent Micro-swimmers): Dozens of palm-sized, autonomous underwater robots would be transported by a cryobot through the ice, then released to explore the ocean, searching for chemical or biological signals. Prototypes have been pool-tested successfully.
PROMETHEUS and related Stone Aerospace projects: Concepts for nuclear-powered cryobots (compatible with Kilopower-style reactors) capable of controlled descent through ~20 km of ice in under a year, with active navigation and science instruments. Prototypes and model validation tests in cryogenic conditions are ongoing.
Hybrid approaches like SLUSH: Combines mechanical rotary-percussive drilling with hot-point melting for efficiency and to handle “dirty” ice with particulates. NASA TechPort projects continue maturing these.
Other tech: Laser-based drills for lower power/mass, through-ice communication systems (e.g., acoustic or fiber-optic tethers), and autonomy software. A 2023 NASA workshop outlined a roadmap, concluding cryobots are feasible and scientifically compelling for in-situ ocean access.
Field analogs include tests in Antarctic subglacial lakes or glaciers (e.g., ORCAA project using cryobots on Earth ice to simulate Europa/Enceladus conditions).
European and Other Efforts
ESA’s JUICE mission focuses on remote sensing and radar to characterize ice shells and oceans on Europa, Ganymede, and Callisto—but it does not include a lander or melt probe. No dedicated ESA cryobot mission is confirmed, though Enceladus has been discussed as a high-priority target for future large-class missions (potentially with plume sampling or orbiter/lander elements). Concepts for melt probes have been studied historically.
International ideas include hybrid drills and even speculative fusion or high-power concepts, but these remain early-stage.
Current Status and Timeline
No approved flight mission yet deploys a cryobot—these are technology maturation efforts (NASA SBIRs, NIAC, TechPort projects) and concept studies. Europa Clipper and JUICE will provide crucial data on ice thickness, composition, and plumes to inform future designs. A full cryobot mission (lander + probe + possible submersible) could launch in the 2030s–2040s if prioritized, with descent times modeled from days (high-power/hot probes) to years.
Recent advances (as of 2025–2026) include laser drills, improved electronics for cold/radiation, and swarm robot tests. These technologies also have Earth applications (e.g., Antarctic exploration).
In short, while no probe is en route, cryobot development is active and progressing steadily as the most promising near-term path to directly sample subsurface oceans on icy moons. Follow updates from NASA JPL, ESA, and planetary science conferences for the latest prototypes and mission proposals.
Mercury Rover
Fraser Cain
https://www.youtube.com/watch?v=TV_kJYQctvk&t=814s
A Cyberdyne Systems Model 101 should be able to handle all that Mercury can throw at it.
Everyone knows that Mercury is tidally locked, the first probe sent there even proved it!
Trivially rebutted. Cite please.
Sigh, learn some history and get a sense of humour.
Google it, it’s funny (in a nerdy way).
On the plus side instead of carrying a big, heavy isotope generator, you can probably power this one with a solar cell the size of a coin
OK, I know it’s a stupid question but since there is very little atmosphere on Mercury to transfer heat couldn’t the rover survive on the day side by simply using an “umbrella”? The Artemis heat shield survived around 3,000C so we have material that can withstand the heat, and with little atmospheric heat transfer as far as I can see this might work. Oh and we shouldn’t call it an umbrella, we should call it a parasol.
PICA heat shields, or any ablative heat shields, are not really suited for 2100 hour heat soak at a temperature that would merely pyrolyze it in a gradual manner (it’s also not intumescent, and if it were, it wouldn’t last). Having a material that can withstand a plasma torch for minutes doesn’t extrapolate to something to, say, shelter under to survive a forest fire that lasts for months.
The Parker Solar Probe is closer to what we’d need, but it too only zips past the sun in a highly eccentric orbit at over 100 km/s, spending mere days under full heat flux
https://www.nasa.gov/solar-system/traveling-to-the-sun-why-wont-parker-solar-probe-melt/
https://en.wikipedia.org/wiki/Parker_Solar_Probe
Let’s say we have a very low emissivity sunshield like the one on JSWT, but high temperature proof, then there would still be radiative heat transfer from the IR glow of the ground at the edges of it. And whatever heat seeps underneath it will accumulate, with only the previously cooled-down and covered regolith to act as a sink.
On the bright side, one could run the numbers and see where such an approach would end up at. I suppose it’ll allow a rover to survive single digit days in that heat. And even if we had made it through the days.. then what about the cold?
Hmm.. looks like we’re gonna have to land at night….
Like my manned mission to the Sun!
Thanks for the great reply.