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.

[ljk4-1]

Tell me this wouldn't be useful for an Europan ocean probe:

A SUBMERSIBLE HOLOGRAPHIC MICROSCOPE. A new device allows
scientists to form 3D images of tiny marine organisms at depths as
great as 100 m. The device allows the recording of behavioral
characteristics of zooplankton and other marine organisms in their
natural environment without having to bring specimens to the
surface for examination. Scientists at Dalhousie University in
Halifax, Canada, used the hologram arrangement originally invented
by Denis Gabor: light from a laser is focused on a pinhole that acts
as a point source of light if the size of the hole is comparable to
the wavelength of light. The spherical waves that emanate from the
pinhole illuminate a sample of sea water. Waves scattered by
objects in the sea water then combine at the chip of a CCD camera
with un-scattered waves (the reference wave) from the pin hole to
form a digitized interference pattern or hologram. The digital
holograms are then sent to a computer where they are digitally
reconstructed with specially developed software to provide images of
the objects. The Dalhousie researchers packaged their holography
apparatus in such a way that the laser and digital camera parts are
in separate watertight containers, while the object plane is left
open (see figure at http://www.aip.org/png/2006/255.htm ). One
difficulty was to get container windows of optical quality that are
thin enough for high resolution imaging but thick enough to resist
sea pressure. The new submersible microscope can also record the
trajectories of organisms in the sample volume so that movies of the
swimming characteristics of micron size marine organisms can easily
be produced. Holograms with1024 x 1024 pixels can be recorded at 7
to 10 frames/s. This requires a large bandwidth for data
transmission to a surface vessel and was accomplished with water
tight Ethernet cables. Imaging volumes can be several cubic
centimeters depending on the desired resolution. The Gabor geometry
allowed the Dalhousie researchers to design a very simple instrument
capable of wavelength limited resolution of marine organisms in
their natural environment. Past generations of submersible
holographic microscopes had lower resolution, weighed several tons,
had to be deployed from large ships, and used high-resolution film
as the hologram recording medium. This meant that only a small
number of holograms could be recorded. In contrast, the Dalhousie
instrument only weighs 20 kg, can be deployed from small boats or
even pleasure vessels, and can record thousands of holograms in a
few minutes so that the motion of aquatic organisms can be captured
in detail. (Jericho et al., Review of Scientific Instruments,
upcoming article; contact M.H. Jericho, Dalhousie University,
jericho@fizz.phys.dal.ca, and also the Universidad Nacional de
Columbia)

***********
PHYSICS NEWS UPDATE is a digest of physics news items arising
from physics meetings, physics journals, newspapers and
magazines, and other news sources. It is provided free of charge
as a way of broadly disseminating information about physics and
physicists. For that reason, you are free to post it, if you like,
where others can read it, providing only that you credit AIP.
Physics News Update appears approximately once a week.