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.

[Guest_Richard Trigaux_*]

There are three ways to protect electronics from radiations:

-shielding. An overal shield is out of question, due to its weight. But some crucial parts could be shielded with some very local shields, like power transistors in a DC-CD converter (which can break from a single event, and are critical). A CCD camera chip can also be shielded, classical shield behind, and lead glass optics in front

-short working time. As JRehling and Bob Shaw say, there is no need of a camera working for months, at least not on a static lander.

-hardened electronics. This is about a variety of techniques used to make electronic parts, especially semiconductors, less sensitive to radiations. But this is difficult, and not much can be gained, say one or two orders of magnitude, and that is not enough on Europa. So I suggest to use completelly different methods, such as triodes or electrostatic microrelays, as I already explained on the Venus lander thread.


An alternative to a simple lander would be a very low orbiter. Its orbit could be set to decay little by little, so that it would graze the ground, allowing to send quantities of very high resolution images, showing things like pebbles on large regions. Of course, it would impact the ground sooner or later, with too much speed o survive. But by letting a rope hang to the ground, we could obtain some free braking, before using a rocket to end braking.



Europa ground looks smooth from altitude, but it is likely a kind of ice regolite, with large blocks, pebbles, and much sand. Worse, it seems that there are many equilibrium slopes, so that climbing them would result in avalanches. A rover nightmare!

So, rather than wheels, it would require a kind of large spider, working with some hydraulic system, like scorpio legs. This could make very long legs with a reasonable weight.

But I think that, fortunately, the most interesting regions are the reddish chaotic regions, which formed with breaking and melting of the ice crust. As there was liquid water on the surface, it frozen hard, not in blocks. So, between the small hills if the chaotic regions, there must be flat hard regions, the most interesting place to find chemmicals or biological particules into the ice. The best place to search, and the best place to land...

Three techniques:
-the homing missile, using a high resolution picture to land on a selected place. Variant 1, with a rocket to land at small speed
-same, but variant 2, lands at high speed and buries itself in ice.
-the airbags, which we can expect they will bounce toward a bottom, precisely where we want to go.

Eventually a cluster of small landers with only such crude guidance, have much chances to land, at least one, in the right place. It would be short lived landers, but with analysis tools, microscope, etc. A small chemical heater could melt some ice.


A lander with a long lived seismometre could land in the same way into the same place, where it would find solid ice to operate properly. The variant with a high speed landing is prefered, because it would provide a shielding against radiations.

[mchan]

Its orbit could be set to decay little by little, so that it would graze the ground, allowing to send quantities of very high resolution images, showing things like pebbles on large regions. Of course, it would impact the ground sooner or later, with too much speed o survive. But by letting a rope hang to the ground, we could obtain some free braking, before using a rocket to end braking.

Besides the ACME-ish imagery conjured up by this concept, the smear control will be a challenge. Without compensating for imager to target relative motion, the images will probably look like something out of the trip fantastique from the film 2001.