According to Adam Smith writing in the Independent about the object that was recently observed in a photo taken from the Yutu-2 lunar rover:

(t)he strange cube was spotted on the horizon around 80 metres from the rover’s location in the Von Kármán crater in November, next to an impact crater.

Yut(u) 2 will spend the next two to three months moving across the crater to get a closer look at the object which is more likely to be a large boulder than anything else (...)

Can someone please explain why the rover, which can travel at a speed of 200 metres per hour - as is mentioned in the same article - will take "two to three months" to move to get a closer look at an object that is 80 metres away.

Perhaps there is mistake in one or more of these numbers, or perhaps there is an explanation for what, on the face of it, seems an absurdly long time?


1 Answer 1


just fyi there's a nice write-up of the situation (and "excitement") in Gizmodo's Chinese Rover to Investigate ‘Mysterious Hut’ Spotted on Far Side of Moon

I'm going to speculate that the faux-monolith is not going anywhere any time soon, so there's simply no rush whatsoever.

Since every meter of rover travel is inherently dangerous (so many things that can go wrong) it makes most sense to maximize the science obtained from of each bit of roving.

Being an apparently "funny shaped rock" in the distance does not suggest that it is likely to yield much science just because it happens to appear from far away to be funny shaped. Therefore it's probably considered by the mission planners to be very low priority.

All automated rovers on all bodies move on average far slower than their top speeds.

One reason is already alluded to above; they are movers of their scientific instruments, and those instruments can take quite a while to do their thing before they are ready for the rover to move to the next site. Modern rovers last for years, sometimes a decade or more. There is no rush.

If 200 m/h or 3.3 m/min is its top speed, that's going to be on flat, smooth, obstacle-free ​and relatively firm regolith. If any of those are not true between the rover and the funny looking rock (and most likely most of them are not true) then the actual speed can be limited by the obstacle avoidance and route-planning techniques they are using.

Per Wikipedia's Yutu-2 the rover has moved about 840 meters in about three years. Don't expect much change in that.

While the Curiosity and Perseverance rovers on Mars have developed over the years semi-autonomous obstacle detection and route planning, I think that Yutu-2 is not using this, but instead its movements around rocks, "sand-traps" and other potentially dangerous obstacles are carefully planned on Earth and instructions are sent regularly via links with the Queqiao relay satellite.

For some solar + battery powered rovers there are power limitations, but in this case with a relatively low mass rover in 1/6 of Earth gravity, I think it moves so slow that it can run directly off solar and doesn't need to worry about cycling its batteries.

  • $\begingroup$ @CamilleGoudeseune Thanks for being gentle, but I have to put that parenthetical "most" caveat back in because it is exactly what I want to emphasize. $\endgroup$
    – uhoh
    Commented Dec 7, 2021 at 3:24
  • $\begingroup$ The other things is, Yutu-2 might have more other "real" science investigations to undertake & if it does they will take time. Yutu-2 was sent to the Moon to investigate a region of the Moon, not necessarily to go chasing unusual shaped objects that might get noticed. I get the impression the Chinese are a bit more nuanced than the Soviets were when they operated the lunokhods on the Moon & one of the progress indicators was meters, meters, meters. $\endgroup$
    – Fred
    Commented Dec 7, 2021 at 9:02
  • $\begingroup$ @Fred I think there's a great new question or two in there! Of course almost 50 years later, the diversity and richness of measurements and investigations that a rover can do at a given spot has changes quite a lot. Direct imaging and just plain looking around was a much larger fraction of what the Lunokhod rovers' capabilities were. So the nuancing disparity comes from epoch differences rather than cultural or space agency differences. I assume that's what you meant. $\endgroup$
    – uhoh
    Commented Dec 7, 2021 at 9:25

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