The First Europa Lander, What can be done first, cheapest & best? Options

[nprev]

I think that many people in this forum would agree that somebody's going to have to land on Europa someday before the rather elaborate schemes to penetrate the outer ice layer will ever fly, if for no other reason than to get some relevant ground truth before committing to such an elaborate, expensive, and risky mission.

EO seems to have ruled out any surface science package for that mission (though it would be nice to change their minds! ), but I think that there is a valid requirement at some point to directly assess the surface properties of Europa in an inexpensive yet creative way. Some candidate instrument payloads might be:

1. A sonar transducer/receiver set embedded within a penetrometer to determine crust density and examine the uniformity of the ice layer within the operational radius of the instrument (looking for cracks and holes, in other words).

2. A conductivity sensor again embedded inside a penetrometer to measure the native salinity of the surrounding material and possibly derive some constraints on the composition of metallic salts in the European crust (saltiness has a major effect on ice properties, in addition to the obvious need to derive the salt content of any underlying ocean).

3. A seismometer for all sorts of reasons.


How does this sound? Any critiques, additions, or subtractions? I omitted a surface imager not only because of bandwidth/extra complexity considerations but also because it seems desirable to penetrate the crust in order to minimize as much as possible reading any contaminants from Io during surface measurements. The orbiter data could be used to sense and subtract this from the penetrometer readings.

[Drkskywxlt]

I think any such impact with the surface of Europa would create so many large fragments (even very small fragments would be damaging at the speed the lander would be going) that a some very heavy protection would be required. That would add further weight and complexity to an already complex mission. I imagine that the fuel required to slow the lander or orbiter to reasonable speeds would be much lighter than any ablative shield to protect the lander from ice and debris thrown up by the impactor.

[AndyG]

The (admittedly ill-fated) penetrators of Deep Space 2, the Mars' impactors carried with MPL in '99, had electronics designed to survive up to 60000g of deceleration.

Assuming a Europa lander hits the surface of Europa at around the local escape velocity (2.02 km/s), then it would need "only" 7m of decelerant in order to bring it to a halt and not exceed that deceleration.

Compressible "somethings" like LEM legs? An airbag? A controlled explosive device fired under the lander when <4 milliseconds from touchdown?

I saw the original animations for the MER entry and landing sequences, and had to laugh at the unlikelihood of everything working just so. These days I wouldn't rule anything out.

Andy