Group2 19-1 Week4

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Notulen tutor meeting

• Make requirements measurable
• Subdivide requirements
• Requirements, preferences and constraints
• Wie gaat het maken? Andere groep stakeholders/gebruikers
• Expand explanation for translation to exoplanets
• Nut van de achievements van de missie
• Wiki hoeft pas klaar te zijn na de presentatie, dus week 8
• Keuze voor experimenten moet echt gemaakt worden, deze week eigenlijk nog'
• Of we in een beschaving mogen/kunnen komen is een ethisch vraagstuk waar we wat meer op in moeten gaan
• Conclusies gaan trekken over constraints en keuzes
• Hoe zeker is er een oceaan op Europa, onze afweging moet duidelijk zijn voordat we ingaan op een cryobot sturen
• Planning weer updaten (week 5 report -> andere tijdsbesteding)
• Modelleren/berekenen
• Anthropologische deontologie
• Zekerheid oceaan

To do voor donderdag:

• Requirements updaten (zie notes Tijn)(Wouter)
• Modelletje temperatuur (Wouter)
• Hoe omgaan met beschavingen (Wouter)
• Experimenten updaten (Marco)
• Planning updaten (Marco)
• Aanwezigheid oceaan bevestigen (Kasper)
• Fiber optic cable at 100 K (Marco)
• Communication options via fiber or alternative options (Kasper)

Week 4 Logbook: Overall

Updated planning

Week 1:

• General research: we explore the topic that we chose and come up with inspiration for a research objective. (Kasper, Marco, Wouter)
  • Deliverables: potential research objectives
• Define users: according to the topic we have chosen, define the users that play a role in achieving this objective. (Kasper, Marco, Wouter)
  • Deliverables: a list of users and their goals with regards to this research

Week 2:

• Determine objective: from the research in week 1, determine a research objective that will be the center of your research. (Kasper, Marco, Wouter)
  • Deliverables: definitive research objective
• Determine requirements for the research objective and its users: in order to achieve an answer to the research objective, what requirements should there be, from the standpoint of the users (Kasper, Marco, Wouter)
  • Deliverables: a list of users and the requirements that they have for this research objective
• Planning: make a planning for the remainder of the course (Kasper)
  • Deliverables: a planning of things that are still to be done for this research
• Consult NASA/ESA: contact NASA and the ESA for their take on how to go about designing a research mission (Marco)
  • Deliverables: advice from NASA/ESA to improve our research

Week 3:

• More extensive user descriptions: further work out what users would be involved with our research objective (Wouter)
  • Deliverables: a more elaborate description of the users and their requirements with regard to the research objective
• More extensive planning: work out the planning of the project in more detail. What should be done when and by who, with which deliverables (Marco)
  • Deliverables: a more detailed planning for the remainder of the course
• Examine possible experiments on Europa: research for different experiments that can be done on Europe to examine our objective.
  • Deliverables: Some experiments that can possibly be executed
• Work out section 3.2: research whether it is feasible and worthwhile to perform research below the surface of Europa (Kasper)
  • Deliverables: a section on whether it is feasible to go below the icy surface of Europa, and, if so, what kind of research to perform there and how to do it

Week 4:

• Work out chapter 2.1: work out how to establish a stable communication between Earth and the lander on Europa (Marco)
  • Deliverables: a description of the necessary technologies to maintain contact with the lander on Europa
• Work out the list of necessary instruments: set up a description of the instruments that the lander should have, along with motivation what they are for and why they are necessary (Marco)
  • Deliverables: a list of instruments, along with their descriptions, functions, and why they pertain to the requirements of the users
• Work out the rest of chapter 2: describe the possible problems that Europan physics pose to the mission, along with possible solutions or workarounds (Wouter)
  • Deliverables: a list of potential Europan physics challenges, along with solutions/alternatives for them
• Work out the rest of chapter 3: how do we get around on the surface of Europa and what conclusions can be drawn from the data of the lander’s instruments? (Kasper)
  • Deliverables: a description of the lander’s mode of locomotion and the conclusions that can be drawn from the data it collects

Week 5

• As week 4: continue to work out the chapters that everyone was assigned to (Kasper, Marco, Wouter)
  • Deliverables: finished chapters 2, 3 and 4
• Research cable testing: investigate the costs of testing a fiber optic cable at temperatures comparable to those on Europa
  • Deliverables: an indication of costs of performing temperature experiments on fiber optic cable

Week 6

• Write conclusion and discussion: write a conclusion that describes the findings of our research, and a discussion that describes what could have been done better/differently (Kasper, Marco)
  • Deliverables: a conclusion and a discussion in the report
• Technical sketch of the lander: make a technical sketch of the lander that showcases in detail what it is expected to look like (Wouter)
  • Deliverables: technical sketch
• Test cable: Investigate whether a fiber optic cable would work at cryogenic temperatures (Kasper, Marco, Wouter)
  • Deliverables: Report on the performance of a fiber optic cable at ~100 K.

Week 7

• Create presentation: create a presentation, to be given in week 8 (Kasper, Marco, Wouter)
  • Deliverables: presentation

Week 8

• Presentation: present our report to the tutors of the course (Kasper, Marco, Wouter)
  • Deliverables: a presentation for a fantastic grade
• Finalize wiki: make sure the wiki is up to date with all our findings and the report that we have written (Kasper, Marco, Wouter)
  • Deliverables: an up-to-date wiki

Updated requirements

User Requirements

These are the requirements based on what the different users want.

External

• 1 Get to Europa
• 2 Build vehicle
  • 2.1 Assuming that if we pay, they’ll be willing to do it, so long as it’s legal

SA’s

• 3 Command vehicle
  • 3.1 Autonomous execution of following category of commands
    • 3.1.1 Go there
    • 3.1.2 Investigate this
• 4 Longevity
  • 4.1 Sufficient energy
  • 4.2 Sufficient durability

Scientists

• 5 Info on Europa
  • 5.1 Atmosphere
    • 5.1.1 Ionosphere; plasma density, magnetic field, current
    • 5.1.2 Density and pressure
  • 5.2 Subsurface ocean
    • 5.2.1 Density
    • 5.2.2 Viscosity
    • 5.2.3 Salinity
  • 5.3 Crust
    • 5.3.1 Terrain
  • 5.4 All
    • 5.4.1 Chemical makeup
• 6 Info on life
  • 6.1 Possibility
    • 6.1.1 Required chemicals
    • 6.1.2 Required environment
  • 6.2 Itself
    • 6.2.1 Chemical makeup
    • 6.2.2 Habitat (Link data of life to data of the habitat)
    • 6.2.3 Enzymes

Life

• 7 Don’t go all genocide on it
  • 7.1 Preserve habitat (as little perturbing as possible)
  • 7.2 Non-lethal research methods
  • 7.3 Sterilised equipment

User Preferences

These are the preferences based on what the different users would like, given unlimited resources.

• Longevity
  • 4.3 Keep up-to-date on vehicle status
    • 4.3.1 Recognise and report on faulty equipment
    • 4.3.2 Possibly repair faulty equipment

• 6 Info on life
  • Itself
    • 6.2.4 DNA
    • 6.2.5 Complexity

Constraints

These are the constraints resulting from the implications of the user requirements and preferences. For instance, 'surviving Europa' implies being able to operate at temperatures between 86 and 132 K.

External

• 1 Get maximum capacity with falcon heavy
  • 1.1 Must fit inside cylindrical capsule: (L=13.1 m, r=2.6 m)
  • 1.2 Must be under 3500 kg (possibly a bit more, but if at all it’s negligible)
• 2 Must be legal

SA’s

• 3 Command
  • 3.1 Autonomous execution
    • 3.1.1 'Go there'
      • 3.1.1.1 Know current and destiny locations
      • 3.1.1.2 Move
      • 3.1.1.3 Recognise obstacles on the way
    • 3.1.2 Investigate this
      • 3.1.2.1 Recognise ‘this’
      • 3.1.2.2 Know how to and be able to investigate ‘this’ (possibly in the command)
• 4 Longevity

Things prone to wear and tear or able to run out should run for at least 2 years. Although costs probably don’t scale proportionally with travel distance of the mission, this Europa mission is bound to be more expensive than Curiosity lander, and should thus last a bit longer than curiosity (was supposed to) to compensate for increased costs. Hence, the minimum survival time of the lander should be about 2 years, both in terms of energy and durability.

• • 4.1 operate for preferably several years, Either:
    • 4.1.1 carry enough energy
    • 4.1.2 Produce energy there (sulfuric compounds/ sun/ magnetic field??)
  • 4.2 Durability
    • 4.2.1 Iono- & Magnetosphere (electromotor?)

Europa's ionosphere Magnetic fields estimated at 5.0*10^-7 T Electron densities of up to 10^10 m^-3 with energies up to 250 eV Ionospheric currents up to .42 A/m

• • • 4.2.2 Low gravity

Calculations of non-uniform gravity Suggestions for zero-G car

• • • 4.2.3 Low atmospheric pressure

Oxygen densities of around 10^-10 that of earth (~1.801*10^23 cm^-2)(see also calculation: Barometric formula) 3D-Plasma source-sink model Spectrometry model Monte Carlo model

• • • 4.2.4 Low temperatures

86-132 K Europan temperature

• • • 4.2.5 Possibly rough or slippery surface

Bases should be able to maintain their position on the surface

• • • 4.2.6 Withstand tectonic activity

Life

• 7 Don't kill
  • 7.2 Research methods that don’t kill the subject
  • 7.3 No biological earthly life brought along on the mission

Measurability requirements and constraints

These are the conditions to be fulfilled in order for the main requirements to be met.

1. The requirement to actually get to Europa has been laid into the hands of SpaceX. Requirement 1 has been fulfilled if the total lander system fits inside a capsule with a length of 13.1 m and a radius of 2.6 m, and is no heavier than 3500 kg.
2. Requirement 2, which asks for the lander system to be built, is fulfilled if the lander system contains only technology which is legal right off the bat, or for which it is possible to get a permit.
3. The requirement of autonomous execution of commands will be fulfilled if the vehicle has systems in place that allow it to know where it is, where it should end up, and how to get there without colliding with obstacles. Furthermore, it should be able to receive commands to research the things specified under requirements 5 and 6, it should be able to find these things, and know how to research them.
4. Requirement of survival is met if the lander system carries enough energy to sustain itself for at least 2 years or can produce on the spot enough energy for that period of time. Furthermore, it should hold on for these two years under the following conditions:
   1. External magnetic field of up to 1 mT, 2000 times stronger than what is estimated for Europa’s magnetosphere. Furthermore, the lander system should hold up at plasma densities of up to 10^10 m^-3.
   2. The lander system should still function at gravities down to 10% of earth’s and should be able to account for a non-uniform gravity not always perpendicular to the surface.
   3. The lander system can still operate under pressures down to 10^-10 atmospheres. At the same time, the digger must be able to withstand pressures of at least 105 atm, and preferably up to 3000 atm.
   4. Temperatures between 86 and 132 K do not damage the lander system and its components, nor make it thusly prone to damage that normal operation will result in damage to the system.
   5. System bases (components of the system that do not move around on Europa) should be able to maintain a fixed position on or in Europa.
   6. The lander system should not be destroyed by the tectonic activity of Europa.
   7. Preference for survival is met if the lander system can recognise faulty equipment and report on it, and can repair or replace said equipment.
5. Requirement of planet research will be met if the lander system can gather data on the aforementioned aspects of Europa.
6. Point a. can be deduced from requirement 5, but to that end point 5 should be expanded to include the criteria for life. Point b. will be met if the lander system can gather data on the aforementioned aspects of any life found on Europa.
7. The requirement of ethical treatment of life and its environment will be met if research can be conducted in such a way as to avoid unethical harm done to relevant moral agents.

Week 4 Logbook: Research

Updated experiments

Seismic experiments:

A seismometer can be used by the lander to determine the thickness of the ice of Europa’s crust, and possible determine a suitable entry point for the ice digger to start digging at. Furthermore, the seismic experiments may also result in observations about the size of the underwater ocean(s), giving scientists new data to correlate already made observations to.

Spectrometry experiments:

Spectrometric experiments should be performed on the ice to determine its molecular composition. These spectrometric experiments will also tell us whether unusual molecules/elements are present in the ice, and even whether there are molecules present that are either of an organism, or they could sustain living organisms.

Not only should these spectrometric experiments be performed on the surface, the digger should also carry spectrometric equipment, such that these experiments can also be performed under the ice, on the underlying water. As with the experiments to be performed on the surface, the experiments performed below the surface will tell us the composition of the water, and whether there are any unusual molecules/elements present, including molecules that indicate life or a capability for life to be sustained there.

Photos:

Taking photos from the surface of Europa is not only cool, if the lander is equipped with a microscope or a likewise instrument, we may also find evidence or traces of life, similar to how fossils and microscopic organisms on Earth provide evidence of past and present life. Of course, the surface is not the only thing that should be photographed. Having a camera on board of the digger will enable photos of the ocean to also be taken. These photos could reveal the internal structure of Europa, or, in the very best case scenario, living organisms themselves in the ocean.

Gas emission experiments:

Similar to how the Viking landers performed gas release experiments on Mars, the same experiments could be performed on Europa. If a small sample of soil, or, in this case, ice, is injected with radioactively labeled nutrients, the release of metabolised molecules may indicate that life is present. These gas emission experiments can not only be performed to find organisms that metabolise to CO2, it can also used to find organisms that metabolise CO2 itself, for example photosynthetic organisms.

Presence of an ocean

The first theories that Europa has a sub-surface ocean came after the fly-by mission of Voyager 1. This spacecraft was, in march 1979, the first that made images in significant detail of Europa’s surface, with a resolution of about 2 kilometers per pixel. These images revealed a surprisingly smooth surface, brighter than that of earth’s moon, crisscrossed with numerous bands and ridges. Researchers noted that some of the dark bands had opposite sides that matched extremely well, comparable to pieces of a jigsaw puzzle. These cracks had separated, and dark, icy material appeared to have flowed into the opened gaps, suggesting that the surface had been active at some time in the past. The images also showed only a handful of big craters, which are expected to build up over billions of years as the planetary surface is bombarded by meteorite, until the surface is covered in craters. Thus, a lack of much craters suggested that Europa’s surface was relatively young and implied that something erased the craters, such as icy, volcanic flows. Next to that, scientist found patterns of some of the longest linear features in the images that did not match the predicted patterns of the features, created by tides as Europa orbits Jupiter. They determined that the found patterns would fit very well if Europa’s surface could move independently and was not locked to the rest of the interior.

These interesting findings led to the next mission to Europa, Galileo. This spacecraft was launched in 1989 and entered orbit around Jupiter in 1995. Galileo eventually made 12 close flybys of the icy moon, including images of Europa at a range of scales, revealing new details about the surface and providing context for how those details were related to the moon as a whole.

One important measurement made by the Galileo mission showed how Jupiter’s magnetic field was disrupted in the space around Europa, implying that a special type of magnetic field is being created within Europa by a deep layer of some electrically conductive fluid beneath the surface. Scientists belief, based on Europa’s icy composition, that the most likely material to create this magnetic signature is a global ocean of salty water. Above described are four strong indications of a sub-surface ocean on Europa, which is why the common belief under scientists is that the ocean really exists. (https://europa.nasa.gov/about-europa/ocean/)

Physical considerations about the presence of water on Europa

Phase diagram of water

One of the reasons to assume that water won’t be present in its liquid form on Europa is in the phase diagram of water, shown to the right. As can be seen in the image, the lowest pressure at which water can still exist in liquid form is its triple point at 611.73 Pa (0.0061 atm), at the common freezing temperature of 273.15 K (0 degrees C). Below that pressure, water has no liquid form. Since the pressure at Europa’s surface is about 10^-10 atm, this means that liquid water can not stably exist on Europa. It may surface for a brief moment, but will almost instantaneously either freeze or boil, leaving no water remaining.

It should be noted that indeed this diagram does not extend below 10^-5 atm, and that based on this image it is thus technically not possible to say that water does not have a liquid form at such ultra-low pressures. However, it is first of all unlikely that such an out-of-place phase change exists based on this and other phase diagrams. Secondly, this ‘liquid’ may not be liquid as we know it and still be unable to support life. Much like solid water has different crystalline structures at different temperatures and pressures, so can this liquid water have very different properties based on the environment it is in. Hence based purely on physical grounds it is unlikely that liquid water in a familiar form exists on the surface of Europa.

Modelling temperature of the digger

A 10x1 digger in near vacuum air with a 1 kW power source

The 10x1 digger in ice with a 100 kW power source

The 10x1 digger in ice with a 200 kW power source

The following data was used for making the model, all derived from Engineeringtoolbox

Thermal conductivities (W/m K): Stainless steel: 14.35 Ice: 2.18 Air: 0.06

Specific heat: (J/kg K) Air: 700 Steel: 500

Densities: (kg m^-3) Steel: 7850

(Matlab’s PDE solver didn’t seem to be able to work with convection, and was not able to make 3D models. WebNutils proved unable to work with solids and multiple domains, and modelling steel as a super-dense fluid with an ultra-high viscosity doesn’t increase trust in the model. Instead, I used Quickfield Student Edition to make the following pictures. This did have the disbenefit of modelling over only 255 data points.)

In the following pictures, the digger will be modeled as being somewhat pill-shaped: a 9 m long cylinder with a 1 m radius, capped off with a hemisphere of the same radius. Both are modelled as being solid steel. The models are axially symmetric, with the bottom border of the picture always forming the axis of symmetry. The other outside borders are always set to be -175 oC (~100 K) to simulate the environment. The models are steady-state, as it is assumed that the digger will be digging through the ice long enough for the temperature to equilibrate. The bit of air around the digger was incorporated in the model to account for the fact that the slow progression of the digger may heat the ice or air around it a little, thereby insulating the digger somewhat. The power source was always adjusted such that it homogeneously produced the desired power.

The upper left image is modelled in air with a 1 kW power source. In this case, it is visible that the digger will have trouble maintaining a sufficient temperature gradient around the power source, as the steel around it effectively takes away the thermal energy but is unable to give it to the environment. This implies that an RTG, as well as other devices that require temperature gradients may not work efficiently in these conditions.

A smaller digger with a 10 kW power source

The two pictures to the right show the digger in ice with a power source of 100 (above) and 200 kW (below). In this case the gradient forms, as the digger can lose its heat, but is not sufficiently large. Even at 200 kW the total temperature difference is only 50 K, and the difference between the in- and outside of the power source is only 15 K.

The solution may be found in the last model, where the digger has been scaled down by a factor of 3.28 (m have been set to ft), yet the power per unit volume was still scaled to produce similar powers. The result (seen on the bottom left) is a much more localised power source capable of producing much stronger temperature gradients. In this case, the total power was 10 kW (10 times less than the other models), yet the total difference is twice as high. Taking into account that this difference occurs over a 3.28 times shorter difference, means that the gradient can already become up to 6.5 times larger.

Communication options via fiber

Fiber-optic communication

Is a method of transmitting information from one place to another by sending pulses of light through an optical fiber.

Fiber-optic use in missions:

In the ARTEMIS mission in 2015 a fiber optic link was used. The function of this fiber was to monitor ARTEMIS under water and allow the scientists to display the real time outputs of the sensors on a screen. There were high noise levels on some sensors. The fiber was 15 km long, but ARTEMIS was at its maximum 10 km from the base. Due to the ocean currents the fiber couldn’t be re-used. Navigation and Communications Under and Through the Ice in Antarctica The ARTEMIS under‐ice AUV docking system

Glass fiber:

• Tensile strength in touch up to 300 degrees of Celsius. Can’t find any information about the tensile strength in freezing temperatures
• Very high tensile strength (3445 MPa for E-glass)
• 100% insensitive for interferential signals, for example from electromagnetic fields.
• Density E-glass: 2.58 g/cm^3. With a typical diameter between 3.8 and 20 µm.

With the smallest diameter, an glass fiber of 10 km would weight only 0,29 gram. With a diameter of 20 µm, the fiber would weight 8,1 gram Glass fibre

“The cryobot uses the laser energy to heat water with which to melt the ice in front of it, while the water re-freezes behind it around the fiber, allowing communications and power flow to be maintained.” (Link used before) Tunneling Cryobot Robot May Explore Icy Moons

Fiber optic cable in extreme conditions

Multiple websites mention that fiber optic cables are quite vulnerable to cold temperatures. Being installed in an environment that is too cold, fiber optic cables may suddenly stop working. Ways to protect the fiber optics from these misfortunes, is to put a bigger sleeve around the cable.

Wireless communication under water

According to an article by Trumbo, Brown and Hand (Salt sea), the surface of Europa has been found to contain sodium chloride. This means that it is a reasonable assumption that the oceans on Europa also contain salty water. Because salty water is a good conductor, wireless communication by means of radio waves is not reliable. The radio waves would only last for short distances within the water, which would not give a high degree of freedom when navigating the ocean of Europa. Acoustic communication, on the other hand, would be more reliable, even at long distances. One such system, dubbed JANUS, has achieved communication distances of up to 28 km, but it is optimized for distances up to 10 km (JANUS). One drawback of an acoustic system, however, is the relatively low throughput. Along with this low throughput comes a tradeoff that has to be made underwater. For short distances underwater, high frequencies should be used, which deliver a high bandwidth, but only for short distances. Conversely, low frequencies can be used to communicate over long(er) distances, but their bandwidth is much smaller (JANUS: the genesis)

Where to place a sub-crust base

To allow for a sub-crust (SC) base that maintains wired contact with the surface base, the SC base must maintain a fixed position with the cable locked inside the ice. Otherwise the connecting cable is highly likely to break due to convective stresses. Another solution would be to make a (partially) stronger cable that can withstand these stresses, but this will increase the carry load and if the strong cable is somehow detached from the ice, the cable will break anyway. However, the submarine does need to be able to detach from the SC base and sail away. Most conveniently, the SC base would be half still lodged in the ice, and half sticking out into the sea below the ice.

Considering this, a problem arises. The viscosity of water increases with increasing pressure (Water viscosity under pressure), as well as with increasing salinity: The viscosity of seawater is up to 8% higher than that of pure water. This means that the ocean just below the Europan crust may have a significantly higher viscosity than pure water. Furthermore, erosion due to convective processes in the ocean may result in a slushy water texture just below the Europan crust. If this is indeed the case, it adds a different requirement, namely for the submarine to be able to navigate and communicate through slushy or viscous water. There is no gradient transition between ice and water in a frozen lake. This means that once you are through the ice, there is only more water, not some substance that is chemically in between ice and water. Due to the scale and tectonic activity of the ice crust on Europa, this might be entirely different, but the Earthly example would imply no gradient. Furthermore, as of yet, the most probable explanations for ridge formation would not work with a viscous or slushy subsurface ocean, or a crust up to 10 km thick. (Europa: The ocean moon, p 117-132) It is thus unlikely that the mission will encounter problematically viscous water, but for the off chance that the submarine does need to navigate through slushy water, it is best to assume viscous water and account for it.

Where to land?

To avoid an overly complex digger, it is likely most convenient to land right on the spot where the digger should enter the crust. Since the digger mainly uses the pull of gravity to dig down, the non-uniform gravity may prevent the digger from digging straight. The only places on Europa where gravity points towards the Europan core are the Jovian and anti-Jovian poles. A slight deviation from the poles is unlikely to prove problematic, as this will not result in too great an increase in the digging distance, but especially at the north, south, leading and trailing poles, the increase can become greater than 200 m.

Furthermore, as most cracks in the crust are mostly vertical, digging straight down decreases the chance of a crack intersecting with the line connecting the SC and surface base. Then the consideration is between the Jovian and anti-Jovian poles. At the anti-Jovian pole, Jupe-Jupe’s gravity helps the digger get through the crust, whereas at the Jovian pole, Jupe-Jupe tries to pull the digger up. Verify: Furthermore, the crust is probably thinner at the Jovian side, but also more tectonically active.

Is it possible to go to the seafloor?

There are 2 main theories for the origin of life on earth: The prebiotic soup theory and the pioneer organism theory. Debating the origin of life The latter is based in a hot, volcanic and sulfur-rich world. Considering the abundance of sulfur on Europa’s surface and the likelihood of Europa being heated by its own core, a pioneer organism process could take place on Europa. Hence, to find life it is worthwhile to investigate the bottom of the ocean, where said heating takes place. Pioneer organism theory

The question that immediately arises is whether this is possible. Europa’s oceans are estimated to be 150 km deep. On earth, this would result in a hydrostatic pressure of roughly ρgh=1000*9.81*150,000=1.4715 GPa=14,516 atm. A quick estimation of the pressure in the sea demonstrates that pressure increases roughly linearly with increasing depth as you travel from the surface to the bottom of the sea. Just below the crust, the pressure is between 104 and 161 atmospheres, depending on whether you are on the sub- or anti-Jovian side respectively. This is equivalent to a depth of 1 and 1.6 km in Earth’s oceans. At the bottom of the sea, the pressure ranges from 1961 to 2961 atm, depending on the side, ranging between 20.2 and 30.6 km in depth.

In principle, building a vessel capable of withstanding these pressures is possible. However, it should be noted that such vessels are generally extremely heavy and can only sink and rise once before needing to be reweighted for another dive and more importantly, they generally can not move laterally. Pressure vessels Taking in and expelling water at these pressures for propulsion is very difficult, as in order to be able to expel water, a force greater than pressure x area needs to be exerted outward. For an example, at 0.2 GPa, the force exerted on 1 cm^2 is 20,000 N. Furthermore, holes in the hull compromise the structural integrity, making it more prone to collapse and thus requiring a stronger (and thus presumably heavier) hull. Propellers with an internal motor will be prone to the same problem, which isn’t overcome by moving the motor outside the vessel, as then the motor needs to be a high-pressure vessel itself. A way to overcome this is by introducing driving the propeller with a magnetic field that reaches through the hull of the vessel. Furthermore, the required maximum pressure can be reduced significantly if deep-sea dives are only done on the sub-Jovian side, where the pressure may be more than 30% smaller than on the anti-Jovian side.

What to do with extraterrestrial life

It is, of course, not impossible that a mission to Europa will find life of some form or another. We will then wish to learn from this life, but the ways in which we can ethically allow ourselves to do so may be limited. The question is: How limited? Should we find extraterrestrial life, how does this impact the mission? To answer this question, it is important to first consider the moral value of extraterrestrial life in itself. The following dissertation outlines why all life, terrestrial or not, should be considered to have some intrinsic value. We adopt this view, acknowledging that at the same time extraterrestrial life has extrinsic value as well, as it can serve to further scientific research. The value of extraterrestrial life Furthermore, one should note that if something does not have intrinsic value, this does not mean it should not be preserved. If something has value to something with moral value, it acquires value. So it also goes for the Europan environment, which is important for the life present on it, as well as for our own research purposes.

We will discuss some different forms of life that we might encounter during the mission and how we should handle in each individual case. First of all, sentient versus non-sentient life. If we find life at all, it is far more likely that it will be microbes or other non-intelligent alien life than sentient otherworldly beings. (If we discover alien life) We can say with quite certainty that the majority of the people would give their approval if we want to examine this life during the mission. But if we, against expectations, do find sentient life at Europa, we must know what to do. There are not any ‘guidelines’ that describe what to do in this case, but we can think of how we would react when extraterrestrial life would appear on our own earth in peace. We would be extremely interested in them and would in some way try to communicate with them. But if this possible sentient life would want to communicate with us too, is one answer that can’t be answered.

Second of all, carbon-based life versus non carbon based life. On earth, all known living things on earth are based on the element carbon. But scientists belief that there could be an alternative chemical basis for life, for example silicon-based life. (Silicon based life) There could be creatures in unimaginable forms and capabilities on Europa, so what should we do with that? At least we should leave these creatures in their value, and if they let us know in any form that they are not comfortable with the visit of our robot, we should abort the mission. Another thing that needs to be excluded, is the possibility of contamination and thereby affecting Europa’s environment or ecosystem. Contamination can be done in differenterent ways; via human bacteria that end up on the robot during the construction of it, wear or rust of the metals in the robot or a radioactive source that poisons the environment. The first possible way of contamination, human bacteria, seems to be no problem at all. According to the following source (Freezing bacteria), bacteria die slowly when they are exposed to freezing temperatures. And since the robot is traveling through the space for about 6 years in -270 degrees of Celsius, we can assume that all possible human bacteria died when the robot arrives on Europa. For the second possible way of contamination it is very important that the best non-wearing and non-rusting materials are used in the final design. Radio-active source?

Sentient vs non-sentient What to do with non-carbon-based life forms? What to do with the environment? How to communicate? Don’t contaminate

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