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Europa has 13½% of Earth's surface gravity and no atmosphere, so an optimal landing on Europa might be similar to a classic propulsive Lunar landing. But with up to an hour communication time lag, very different surface materials and topology, radiation and gravitational environment, insolation, temperature.

What are the main similarities and differences of a Europa lander compared to Surveyor, Viking, Philae, Huygens and other landers? How would it be designed? Congressman Culberson who has promoted a NASA Europa lander says 17 minutes into this interview that it could use both the skycrane of MSL and the "airbags" of the MERs. I'm not sure that would be suitable for an airless world, and especially not in combination.

Would a mothership Jupiter orbiter have to reconnaitre Europa's surface during flybys before releasing its lander, or did Galileo map good landings sites? Does the terrain on Europa allow for a rover?

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Yes, you would need to get higher resolution data than we have in order to pick a landing site, even if only for science reasons. You want to get to the "good stuff", which would be exposure of material somewhat recently brought up from the ocean. You would also need to pick a site that meets the requirements of the lander, which would be designed to be as forgiving as possible.

A skycrane is a very good way to get a very low landing velocity, which is step one in a successful landing. Once you have a skycrane, airbags are not necessary since they solve the problem of higher landing velocities. However buried in the airbags was another system that might be useful, which is the ability to right the vehicle from any orientation. Step two is deploying whatever scientific investigation is needed on a hostile surface never before seen, which will require a very robust system.

The current plan is to not have a Europa orbiter, but rather a Jupiter orbiter that does many flybys. This maximizes the science return in the face of the short lifetime of the electronics in the high-radiation environment near Europa. So if there are data relays from the lander to the Jupiter orbiter, they might only be a few passes, and they will need to get a lot of data transferred on each short pass. I suspect that the lander would have both relay comm and a direct-to-Earth link, as our current rovers do on Mars.

Landing and communicating are only part of what needs to be dealt with. The science instruments, what they do, what support they need, what they need to access, how long they need to operate, how they will survive the radiation for that long, how the system will be thermally maintained without vaporizing the terrain around you, all of that will drive the design of the Europa lander.

We will soon begin to understand Clarke's wisdom ...

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Galileo appears to have done optical mapping mostly at 200 meter resolution, with some areas covered at lower resolutions and some as fine as 10-20 meter resolution, which doesn't seem ideal for anything beyond choosing a general area to land in. I don't believe there's been any radar/lidar altimeter mapping done, so (as PearsonArtPhoto notes) a combined orbiter/lander mission would be sensible.

The surface of Europa appears to have some clay-like minerals on it in addition to ice; tectonic activity causes the moon to produce water vapor geysers, which may yield some snowfall, so the terrain is going to be varied and quite different from either the moon or Mars, so I would guess design of a rover would have to be a little different -- spikes on the wheels?

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