Frankly, why is it so hard? The article doesn't really show anything outside dust playing role in the very final stage but most landings failed higher above ground. These days we even have lasers to instantly detect distance to the ground that could be incorporated real-time to thruster output. There is almost no atmosphere for friction so basic Newtonian mechanics should be able to make a decent landing. Orbital mechanics is also out of the question near the ground. Why is this still an unsolved problem?
AFAIK there have only been two attempts by private companies.
SpaceIL's crash in 2019 seems to have been caused by a premature engine shutdown due to a faulty IMU [1].
iSpace's attempt seemed to go well until the very end, when contact with the lander was lost. Their status update from April 26 suggests that also their engine may have shut down prematurely: "engineers monitored the estimated remaining propellant reached at the lower threshold and shortly afterward the descent speed rapidly increased" [2].
If this turns out to be the case, the ultimate culprit may be faulty altimetry.
> These days we even have lasers to instantly detect distance to the ground that could be incorporated real-time to thruster output.
Yes, but lasers don't work well through dust clouds, and throttling rocket engines is hard. You can't smoothly reduce thrust all the way to 0; even with a sophisticated design, there is a cutoff at something like 20% [3]. So you need to plan ahead, shut down the engine before touchdown and hope that you don't end up hitting a stray boulder - which is all it might take to tip over and bury your antennas in regolith.
How many complex machines (or complex anything) are going to work first time?
Most things require an iterative loop of testing, fixing and refinement.
The trouble with landing on another planet (with different gravity, atmospheric density, etc) is that there's no real way before you get there, therefore first attempts are extremely likely to fail.
> There is almost no atmosphere for friction so basic Newtonian mechanics should be able to make a decent landing
Actually, I think that is the one of the biggest challenges. No atmosphere to slow you down means you have to rely entirely on rockets to slow down from orbital speeds to zero.
Fully autonomous landing in unknown surfaces is still pretty difficult. Still, the Moon should be more forgiving than the Earth - no wind, lower gravity...
No atmosphere - need to brake all of the velocity difference with engines & can't use aerodynamic surfaces or parachutes.
On a body with atmosphere you can essentially just drop a payload up to some maximum size with a proper heat shield and a parashute and it will end up (somewhere) on the surface in one piece.
On an atmosphere less body you essentially need to run precisely controlled flight all the way to touchdown.
A thin atmosphere like mars can make it worse. The actual amount of braking you get is a bit unpredictable, and the size of the aerodynamic surfaces you need to make a significant impact can use up quite a bit of your mass budget (example: despite the size of the Perseverance/Curiosity parachutes, they still needed a sky-crane for final touchdown).
Indeed, Mars is a bit of an annoying edge case here. Still the atmosphere really helps in other regards, such as for orbit circulation for probes via aerobraking. And can be used for aerocapture in the future as well.
Given the Mars gravity I still wonder if no atmosphere would still make it worse vs the thin that it has.
But also, here on earth you go to your backyard and try your landing as many times as you want. While with the moon you have simulations and models of various fidelity.
