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_Myran_*]

Yes I agree with djellison and others.
To give the Europa lander plan the chance to get trough the budgetary squeeze it will have to be the lightest and in some ways simplest kind of lander imaginable. So the actual landing might not even be a 'soft' one but actually take advantage of getting buried to ensure that the lander doesnt die from radiation prematurely.

Then again about radiation, would there be any advantage of landing on Europas trailing side?

A buried or semi-buried lander might also include a simple sampling system.

Imagine adding a radiactive heating element of a similar kind to those the MER are using, such would melt a bit of ice which would pour inside to any choice of sensors the designers could fit into such an instrument package. This one could answer some basic questions such as:

Have the ice on the landing spot ever been circulated in the interior or Europa? Does it contain any gasses? If so which ones?

Have the contents of the sample been changed in any way by radiation?

Lastly: Does it contain anything else but lighter elements? If not, which ones and what are their origin?
Yes I think of possible volcanic matrial from Io of course, if we're very lucky we might get one small peek at an Io sample for free.

[JRehling]

I don't think we can bet that a Europa rover wouldn't land in a hopelessly craggy "warzone" of infinite overlapping crevasses that make roving impossible. A bouncing lander would have an increased chance of settling into such a cranny. Remember that in the case of Mars, smooth at low resolution has tended to mean rough at high resolution and vice versa. On Earth, that's not quite true. So we can't bet on landing on what seems to be a smooth frozen pond and getting a slick, smooth surface: it could be bad news at rover-wheel scales.

I did a quick web-search to see if there are any results from terrestrial radar on the roughness of Europa, but it's clear that terrestrial radar is not well disposed to answer the question: a 2001-published study using 70cm wavelengths didn't even *find* Europa. The icy Galileans are very bright at shorter wavelengths. We know from the best Galileo images that some of Europa looks very rough at 6m/pixel. That is already an important answer for a rover that would want to travel more than 12 m!

Simply put, we can't bet the bank there there exists any Europan terrain that a wheeled vehicle can traverse, so we're not going to invest billions on one and hope for the best.

Furthermore, we don't know if anyplace on Europa is interestingly diverse at rover scales. If we did land on a big smooth homogeneous ice sheet, why rove at all?