PRE2017 3 Groep1

Project statement

Concept

In the year 2032 the Mars One organization plans on landing the first humans on Mars and establish a permantent human colony there. The first humans will start to build an empire by building a base where people are able to live. After a first base is built, it will be developed further and furter. In the end, people on Mars should be able to live there without any help from planet earth. Mars should become a self sustainable environment.

But before we get there, a lot needs to happen. Right now, Mars does not have an atmosphere, so there is hardly any oxygen in the air. All of the water present on Mars is in the form of ice and lies far beneath the surface. Right now, no one is able to live there. Nothing is able to grow there. This needs to change.

In this project, we want to get a step closer to life on Mars. We want to do this by looking into food production on Mars. We chose to focus on the plantation of potatoes, since potatoes are very nutritient and since there has already been done some research on potato plantation on Mars. We chose to for the breed Escort, since this is a long cycle potato. This means it takes about nine months for the potato to grow, but it will get way bigger than short cycle potatoes. In the end this will be more efficient for large scale food production.

For this purpose, we are going to create a fully autonomous greenhouse, which is able to plant and harvest food, to fertilize and to water its crops. The greenhouse we are going to create will consist of four walls and a rounded roof, all filled with a great amount of isolation material. The slightly tilted roof is necessary because of the fact that Mars has no atmosphere. Because there is no atmosphere, rocks and other junk from outer space will fall down on Mars, opposed to what happens on earth, where these rocks burn up in the atmosphere. Whit a slightly tilted roof, everything that falls on top of the roof will slide right off.

The isolation material in the walls and in the roof absorbs all the light coming in from outside the greenhouse. This way, we can create our own earthly cycle inside the greenhouse. This will be done using heating lamps. This is very efficient since the temperature and light can now be controlled by the same conroller. An earthly cycle is favaroble, because we know potatoes will grow under these light circumstances.

Inside the greenhouse, the planting and harvestig will be done by an autonomous farming robot. This robot will be based on robots that are already being used on earth. The robot will look like a tractor. It will come in action only when it gets a signal that the potatoes need to be harvested. The robot will then harvest the entire field, then plow the entire greenhouse. After the ground has been fertilized again, the robot will plant new potatoes.

The fertilization of the greenhouse is also done autonomously. Over the entire greenhouse, sensors will be placed in the ground. These sensors will be measuring the nutritions in the ground, as well as the humidity of the ground. When the sensors measure the humidity or nutritions are below a certain point, they will give off a signal. This signal goes to a connected sprinkler system. This sprinkler system couples to two different tanks, one with just water and another one with diluted manure. The sprinkler system switches between the two tanks depening on what signal it gets. The sprinklers will go off once the sesors detect that the humidity or nutritients are above a certain level again.

Goal

We want to make a fully autonomous greenhouse. We want to try and do this in the form of a model. In this model, we want to conssider the user needs, the strange environment and the considerations of the society and enterprice. Though it is never possible to please every single party, we want to try to compomise as good as possible and get everyone to agree with our techology. But most important, we want the primary users to be happy with the result and we want them to be able to use it in the easiest way possible.

Approach

We want to make our model by first looking at what parties are involved, what their requirements and prefrences are and if there are any constraints. Based on this information, a lot of research needs to be done on the process of farming potatoes, on the environment on Mars, on the already existing greenhouses and on (autonomous) farming robots. All of this information has to be displayed clearly. From here on we can collect hard data (numbers) on what potatoes need (for instance how many water per certain time). This can then be put togheter in a simple MATLAB model.

Planning

Week 5

Aricia: Literature research on nutrients in the Mars ground.

Máire: Include USE aspects in all of the different sections.

Thijs: Literature research on the growth cycle of potatoes.

Wouter: Start with the model and make a list of every variable needed.

Sjoerd: Find the optimal air composition for potatoes and compare it to the current air composition on Mars.

Stefan: Make the planning and find the optimal light intensity for potatoes.

Week 6

USE aspects

Problem statement

There is a mission going on to send a group of people to Mars for colonisation. In the first stage, this group consists of about 20-30 people. After this, every couple of years a new group is sent to Mars. When the first group arrives on Mars, it is important that there are enough recources to sustain. Since the plan is to stay on Mars for the rest of their lives, merely canned food will not do (it will run out fast). Thus food has to be tailed. As there is a limited amount of crew members in the first stage of this mission, it is favourable that as much work is done autonomous by rational agents. One of the most importan things in order to survive, is the tailing and harvesting of food. In the beginning, this should be focussed on nutritious food which is easy to process (grain for instance takes a lot of work to make into something eatable, which is not favarobale at this stage). We chose to look into the tailing of potatoes. This process is not yet fully autonomous.

Objectives

The objective is to make a model in matlab and simulink for an autonomous controlled environment for potato harvest. This includes the harvesting and the planting of the potatoes at right times, as well as keeping the environment ideal for growth.

Aspects

■ Harvesting and planting robot

■ Greenhouse

■ Climate control

■ Water and nutrition supply

Users

The users can be divided into three groups: primary, secondary and tertiary users. The primary users are the users that directly come into contact with or benefit from the technology. The secondary users usually do not directly use the technology, but benefit from it anyway, for instance when they work on the development or design of the project. The tertiary users are mosly involved in purchasing the technology.

Primary users

■ Inhabitants of Mars

The direct users of our technology will ofcourse be the inhabitants of Mars. The technology is designed especially for them, so that their life on Mars gets a bit easier. In the first stage of the Mars mission, all the inhabitants are going to be (mechanical) engineers, doctors, biologists, agriculture experts, physicists etc.. They are all going to be trained in advance to be able to handle all kinds of situations. They will be trained to use the technology that is sent up with them, including our techology. There are no experts for the different kinds of technology though, which means all of the techology needs to be relatively easy to understand.

Secondary users

■ (Mechanical) engineers (on earth)

(Mechanical) engineers are needed in order to design and build the technology on earth.

■ Programmers (on earth)

Programmers are needed in order to make the process of potato tilt fully autonomous. They need to implement all of the research done by other scientists in order to create the perfect environment for potatoes to grow in.

■ Biologists (on earth)

Biologists need to do research on the environment on Mars and in and how growing potatoes is possible in that environment.

■ Agriculture experts (on earth)

Agriculture experts need to establish the perfect kind of potato to grow under these extreme circumstances, as well as they need to determine the perfect conditions for the potatoes in each stage of their growth.

■ Chemists (on earth)

Chemists need to determine how to change the soil and air so that the right nutritients are in there.

■ Physicists (on earth)

Physicists need to calculate how the gravity is going to effect the growth of the plants.

All secondary users descirbed above profit from the technology in the sense that it will be their job to contribute to de development of the technology, so they will get paid to do their jobs.

Tertiary users

■ Buyers of the technology

The buyers of the technology also play an important role of the process. These are the ones paying for everything after all. If they are not happy with the technology, they will not pay, which makes it very important to look at their requirements and prefrences as well. The buyers of our techology will probably be either NASA or the government.

User requirements

Primary users

• In the early stages of the Mars mission, people might not have the knowledge to make any complex modifications or repairs to the robot. This has to be taken into account when the robot is designed. It is important to make a design that is as simple as possible and make the programming as clear as possible. In this case, when something does break down, it will hopefully be easy to fix.

• Another consideration will be the material of the greenhouse. Because the resources are limited, it is important that when the technology disfunctions, it can easily be made without using a lot of materials and specific tools. If certain materials or tools aremight be needed in order to fix the technology, it is important to know in advence so that these can be taken with the crew to Mars.

• The technology needs to be easy to use. Preferably, the technology is fully autonomous so that the crew does not loose precious time while building up Mars.

• The technology needs to be efficient. It is important that, in an environment where there are so little resources, no food, water, manure or energy is wasted.

Secondary users

• Money for research.
• Enough time for research. A lot of the time researchers are set with very strict deadlines in which it is not always possible to deliver the quality of work needed for such a big project.

Tertiary users

• The technology needs to be as cheap as possible.
• The technology needs to have a long lifespan, so that it does not have to be re-purchased.

Society

Apart from the users there are two important groups left to consider, Society and enterprise. The two aspects are intertwined for some part but we will consider them separately.

First off is Society. The entire world population falls under this category because sending a small group to Mars could have a huge impact on the rest of the civilization. The Mars project is a really expensive one where only around 20 people will reap the initial benefits and get sent to Mars. This could cause a lot of uproar about the project, because some people might feel like they are investing billions of euro’s into that small group of people. Initially that feeling would be true, before a second group of people are sent to Mars, the first group is solely benefitting from the autonomous farm. However the autonomous farm could easily be implemented on Earth which would increase the efficiency of growing crops and the technology would therefore not only be used on Mars. So shifting the investment from solely Mars to both Mars and Earth might ease a lot of people into becoming less opposed to the project.

The next group of people that could start to counter the autonomous farm are the farmers. Since the implementation of autonomous farms that are more efficient than farmers could cost a lot of jobs on Earth. Farmers are a really large group of people that would all be opposing something that could eliminate their job altogether. There are different ways to deal with the farmer opposition.

The first possibility is instead of replacing the farmer with the autonomous farm, the farmer actually uses the autonomous farm to do all the hard work for him and the farmer could still distribute and sell his potatoes. However that could still mean a lot of the farmers lose their jobs since the autonomous farm does everything up and till the potatoes are harvested and collected, so distribution would be the only job left to do. And on top of that, the autonomous farms are supposed to be more efficient than a human farmer, meaning there are less farms needed to feed the same population. All things considered, letting the farmers use the autonomous farms still won’t convince them of the benefits of an autonomous farm.

Another approach is to build the autonomous farms, not in more crowded and stable civilizations, but instead in third world countries. Where a single autonomous farm could feed a lot of people, causing the local population to flourish and grow. A sudden growth in population in these countries could have major effects in very different directions. One of the possibilities is that the growth and the flourishment of the country could turn it into an equivalent of the modern western societies with a lot of wisdom and knowledge getting spread throughout the country and eventually leading to a crucial country for innovation on multiple fields. An outcome to wish for, but not guaranteed. On the other hand there is a possibility that the growth of the population causes nothing more than an increasing number of people needing food and water without any progress in education or wealth in the country. With the original reason for the Mars project in mind, which is a second planet for humans so that Earth does not get overpopulated, the second scenario would only be countering the initial motive of the project. Of course in the third world country one or the other outcome could happen, or anything in between, so there is no way to know how an autonomous farm would change the country.

In conclusion the Mars project is one of those subject where there is always a group of people that is either opposed to the project, or a group where the investment and innovation has a negative influence on. But every big revolution and innovation has its opposition, so the Mars project should not be canceled because you can’t make every person happy.

Enterprice

Rounding of society brings us to the last important group, enterprise.

Enterprise is based on corporations and companies looking to make a profit. The Mars project is either worth investing into or not. With the benefits and downsides for society in mind, enterprise revolves around money. The autonomous farm in particular is more efficient than a farmer, so for a big company to own an autonomous farm could be enough to drive out the competition due sheer efficiency of the farm. For the company this could mean a lot of profit and when investing into the autonomous farms means a cheaper and even more efficient outcome, even more profit. But most of the companies have no benefits from investing into an autonomous farm when it will only be used on Mars. They could invest simply for innovation and for the next step of the human race.

RPC's

In this subsection the requirements, preferences and constraints of the technology will be elaborated. With the limited resources, energy and manpower the technology used has to be altered to such an extend that all the different scenarios are to be taken in account. This will prevent early wear on the robot and its surroundings.

Requirements

All requirements are essential for the sustainability for the robot.

• Versatile mobility

The robot that can do multiple things, namely; planting potatoes, harvesting them, eliminate all remains of the potato plant to stimulate better growth for the next cycle, transport the potatoes, and do this while moving in between the different potatoes plants without trampling them. With that all to be taken in account the robots movement has to be versatile and reliable. Versatility is playing a large role in the development of the current technology, since this also lowers the cost of the development of the robot, since the same technology can be used multiple times. Making it more beneficial for the enterprises, making it look better in the eyes of society and by reducing the costs it can be invested in something else needed.

• Efficiency

The means to send materials to Mars are very expensive and thereby very limited. While on earth we will be able to use means like fossil fuels and such, this is not the case on mars, a limited field of solar panels will probably the most reliable source of electricity. Therefore the whole potato harvest process has to be as efficient as possible. Since no speed records has to be set by the robot, one can think of more dramatic ways to increase its efficiency, for instance using in wheel motors to bring friction down to a minimum.

• Ease of transport

A system for transport is of course not difficult to implement in a robot, especially not for a vegetable like potatoes. However the robot has to be compact even when it has a container to store the potatoes temporary. When the robot exceeds a certain size, it will be difficult to maneuver between the potatoes plant with care in a relatively small area. Adding to much way will destroy the loose earth ground maybe even to such an extend that the potatoes plants can’t grow optimally or water that is sprayed on top can’t be absorbed. The last very important thing is that when the robot is larger, its weight will increase, making it less efficient due to the extra weight and resistance it has to overcome to drive. So with this in mind a system that can only carry a very few potatoes at a time might not be such disadvantage.

• Ease of maintance

With only a very limited amount of personnel that will be send to Mars the first years or even decades, it is essential that the amount of required maintenance stays as low as possible. The people staying on Mars will have more important issue’s to worry about, so some compromises might have to be made to keep the maintenance that low. For instance when extra error marges have to be computed for, the robot might get heavier and thus less efficient, these kind of things have to be taken in consideration when designing the robot. But when something breaks in the robot, it has to be able to be fixed or replaced relatively easily. When designing, it can be made with different modules, which can be replaced by reserves that are to be send to Mars.

Preferences

• A connection to Earth

One cannot expect from the people that will be send to Mars that when the robot doesn’t behave like initially intended that they can fix it, that is, when the problem isn’t physical. So when part of the arm doesn’t rotate for an instance, the habitants of the Mars base will probably have to fix it themselves. But the problem can be in the programming of the robot as well, when the robot cannot maneuver through the greenhouse for an instance, which might be due to difference in gravitational pull from the planets. When a connection is to be made between the robot and Earth, people like scientists, programmers and physicists can change things in the programming of the robot. A second benefit of this will be that the people on earth will be able to gather data from the robot. Like tesla is doing with their cars the data can be used to write a new program for the next iteration of the robot.

Constrains

• Size

In some views a very large robot might look like it’s beneficial, but like mentioned earlier, to be able to sustain on Mars, everything has to be as efficient as possible. Often when size increases it tramples efficiency, especially when a robot has to maneuver in a relatively small greenhouse. Making the robot smaller does however come with some challenges, the robot has to have some force for an instance to pull the potato out of the ground. Then while having finished that, drive with the potato to the next potato plant and do the same thing again, with the extra weight of the potato it is carrying around.

Scenario's

Linda

Linda is a women in her mid fourties. She has done two masters in computation science and she has a lot of experience in working with different languages of programming, but she is specialized in only one language. From a very young age, she was interested in outer space, so when the oppurtunity of going to Mars was there, she was the first one to apply. After lots of procedures and years of training, she made it to the final crew and she is now living amongst the first people on Mars.

On Mars, there is a problem with the technology of the autonomous greenhouse. It does not function as it is supposed to do. The system does not react to the sensors anymore. After the crew has checked everything that could be wrong, the conclusion is that the system needs to be rebooted. After the reboot certain parts of the code need to be reevaluated and possibly rewritten. Since Linda is the most experienced person on the crew, this will be her job. However, she finds out the language in which the code is written is not a language she is specialized in.

In order for Linda to solve this problem, it is important that the code is very well commended (in every step of the code it is explained what is happening in that code). It is also important that the code is a simple as possible. Since Linda has a lot of experience with coding, she will be able to understand simple scripts of different languages. Besides these requirements, it is very important that there is a possibility of contact with earth, especially with someone involved in writing the code. This person can help her with the more complicated parts of the code if needed.

Steven

Steven is a 32 year old man. He did a master in … and he has worked with a multidiscipline group on how to produce food on Mars for the people who are going to live there for two years now. He is now very familiar with all the do’s and don’ts when it comes to the cultivation of different crops on Mars.

On Mars, there is a problem with the nutrients in the soil. All the nutrients washed out of the soil thanks to a brief failure in the sprinkler system. Due to this the crops that are already growing in this greenhouse are going to die if the people don’t jump in.

After some checks of the values the sensors in the soil gave and a quick analysis of the soil it turns out that the people need to start fertilizing in the greenhouse so that the soil gets enough nutrients again to let the crops grow.

In order for Steven to solve this problem, it is important that there are enough sensors in the soil to get all the values that are needed to determine what type of fertilizer and how much of it is needed. It is also necessary that there is enough of all the types of fertilizer that are needed on Mars in stock. This way Steven can put together the needed fertilizer and can put in in the system so that it gets spread on time.

Harold

Harold is a 29 year old engineer. He did a master in … and he has been involved in the design of the greenhouse that will be put on Mars for a year now. He joined the group working on the greenhouse to know how it is going to be constructed and to lead the group who is going to build it on Mars.

On Mars, after the greenhouse has been built completely and is already operational for about two months now. All crops are planted and everything was going as planned, but then the sensors in the greenhouse showed that the levels of O₂ and CO₂ where changing rapidly. If the people on Mars don’t spring in all the O₂ and CO₂ will leak out of the greenhouse and all the crops in it will die, because of the hostile environment that is created in the greenhouse.

The crew goes on to check the greenhouse and its surroundings, to discover that one of the side panels was leaking gas out of the greenhouse. To repair this leaking side panel the team decides to temporarily seal the hole by screwing a small iron plate over it. After this temporary fix a new side panel is made to fit this one and it is placed over the old one from the outside. After fixing the one outside the one on the inside is removed and the greenhouse works as it should again.

Assumptions

Since this model will be a very first draft, lots of assumtions and approximations need to be made. All of the made assumptions and approximations will be listed below, including an explenation of why these are valid. Throughout the project, we will try to eliminate as many approximations as possible, in order to make a more detailed model. The assumptions will be divided over a couple of subsections, such as the things we assume the robot can do, the composition of the ground and the growth of a potato. This in order to try and give a clear overview of all the simplifications in our model.

Users

It is important for the developers of the technology to keep in mind what tasks the users can perform. This way the developer can make sure that the technology can be maintaied as well as needed and that the technology will have a long lifetime. For this, a couple of assumptions are made about the primary users.

• The primary users are trained in solving minor problems with all kinds of technology
• There wil be (mechanical) engineers amongst the primary users with the skill of performing a bit more complicated maintenance
• The martian crew will be able to contact earth at all times
• The crew members have minimal knowledge about potato plantation
• The crew members have minimal knowledge of the specific technology

Robot in greenhouse

At the moment, there are no fully autonomous farming robots available that fit in our project. There has been done research though on making tractors autonomous, so our robot in the greenhouse will be based on this research. Since this robot does not yet excist, a lot of assumptions need to be made. All of these assumptions are based on the literature research.

• The robot is able to plant potatoes
• The robot is able to harvest potatoes
• The robot is able to plow the ground
• The robot is able to move forward and backwards
• The robot has a small turning radius
• The robot is able to detect where in the field it is
• The robot can track where in the field it has already been
• The robot can move forwards and sidewards, but it can only plant, harvest and plow in one direction

Ground on Mars

In order to grow potatoes on Mars we need to know what the soil of Mars contains regarding for instance nutritions. Though there has been a lot of research about the soil on Mars (see literature), the exact composition is hard to find. In order to make the soil right for potato growth, it needs to be fertilized. Before this fertilization can be included in the model, a set of assumptions and basic boundary conditions needs to be made.

• The composition of the Martian soil is seen as equally distributed around the whole planet
• The values found in the literature do not include errors
• Only take into account that the potato is able to take up ions from above it (so 10 cm in depth to take up these substances)
• Take size 28/35 potatoes (so width between potatoes in same row 28 cm) if size 35/55 was taken than it should be 38 cm. It is better to have more potatos in the field, therefore, size 28/35 has been taken.
• Each potato is able to get ions half the distance till the next potato.
• If there is shortage in ions in the ground this can be easily dealt with by putting the shortage in the fertilizer.
• Human feces and pee will be enough to fertilize the ground.
• Other crops will also be able to grow on Mars, therefore, the dead plants can also be used to fertilize the ground.

Greenhouse

• The greenhouse is a closed system (every feces or dead plants etc. will be reused)
• The greenhouse is able to set different seasons inside it

Potato tilt

• We will look at the escort potato.
• The surface area of the potato field will be .....
• The size of a fullgrown potato will be .....

Model

In this subsection, a description of our model will be made.

Needed values

■ Air

• Wanted composition
• Composition Mars
• Wanted pressure
• Pressure Mars

■ Soil

• Composition Mars (nitrates)
• Wanted composition (nitrates)
• Humidity Mars
• Wanted humidity

• Potatoes are wet when planted.

• Before emergence: SWT of -20 - -60 kPa

• After emergence and before tuber growth: SWT not lower than 0.3 MPa.

• After initiation tuber growth: SWT of -20 - -60 kPa

• Composition manure

■ Greenhouse

• Size
• Coefficient of heat transfer walls

■ Heat unit

• Capacity
• Energy consumption

■ Potatoes (Escort)

• Development speed
• Stages of development (with accompanying circumstances)
• Size

Greenhouse design

Cosmic radiation

On earth we have the special privilege that we have a relatively dense atmosphere and an active magnetosphere. In the magnetosphere charged particles are affected and manipulated by the magnetic field of an astronomical object, in this case Earth. These charged particles are more usefull for the habitants of Earth than one might think on first hand. For instance the solar winds that occur on our sun launch an cloud of charged particles, this is a plasma, this plasma consists of mostly electrons, protons and alpha particles. These are redirected by our magnetosphere and this creates the phenomenon the northern lights. Mars however doesn’t have the magnetosphere, because it doesn’t have it, the solar winds, charged particle and other cosmic radiation reach the ionosphere of Mars directly. The cosmic radiation then strips away (air)particles from Mars, making for a very rarefied atmosphere in comparison with that of Earth. The cosmic radiation also reaches the surface of Mars, and if the greenhouse would be made out of a transparent material, it would also reach the potato plants. When plants come in contact with the cosmic radiation, it can change the DNA of the plants with consequences that can differ from situation to situation, for an instance it can make them inedible, kill them off completely, or make them grow even faster. Some scientist are however not completely sure what will happen, because the plants that are on Earth now have been through millions of years of relatively low cosmic radiation. But to ensure the plants will stay roughly the same a completely sealed greenhouse will be build. It is not possible to stop cosmic radiation, what we can do is break it up. When one breaks the particles up in even smaller particles they become less harmful. Materials that are good at breaking the particles up are materials that are as small as possible. The best are Hydrogen, Boron, and Nitrogen. Now it is very important that the materials can be used as a building block as well, the materials can of course be used as extra layers in between the building and structural layers. But with efficiency in mind, for transport (the flight to Mars) and the building ofcourse, the walls can better be build out of these materials as a whole or at least for the largest part. The boron nitride nanotube is for this purpose a very good option. It has the shielding capabilities needed while remaining strong building capabilities. The boron especially is very effective at breaking the neutrons, the nitrogen doesn’t reach those standards but it also breaks the neutrons pretty effectively.

Summary literature search

Soil on Mars

Climate change on the planet Mars by detection of ground ice. The water layer is 10 - 40 cm thick and occurs in between latitudes of 30 degrees and 60 degrees. This means that water is available on Mars. Because of this carbonates can be produced. The exact substances will be discussed below.

Ions

A layer of ice has been found at a depth of 5 – 15 cm deep. In the soils around the Phoenix landing site calciumcarbonate has been discovered (3-5 wt%) by scanning calorimetry. It showed an endothermic transition at around 725 degrees Celsius accompanied by the evolution of calciumcarbonate and the soil had the ability to buffer pH against acid addition. It formation in the past was due to interaction of the atmospheric CO2 and the water on particle surfaces. The Martian soil has been further looked into, where around 10mM of dissolved salts have been found out of which 0.4 – 0.6 % perchlorate (ClO4). The other negatively charged ions included small concentrations of bicarbonate, chloride and possibly sulfate. The cations detected (positively charged ions) included Magnesium, natrium and small concentration of Kalium and calcium. Besides this, an alkaline pH was measures of 7.7 (with a marge of 0.5). These findings included that the soil at Mars has changed of the past years due to the action liquid water. It has also been found out that there is mechanism to place ice at the surface: clouds of ice crystals precipitated back to the surface and formed a daily basis. Even though ions have been found, nitrate is an important ion for the Martian soil to be able to grow crops. In the table below, the concenrtations of a few ions are given.

Nitrate should naturally be formed through the oxidation of atmospheric N and then accumulate on the surface. On Mars odd nitrogen (N and NO) can eventually be turned into NO2, which can form nitric acid. Nitrate, thus, has not yet been detected on Mars: there are only some possible detections. In table 3 multiple acid formations can be seen.

These results are bases on the Phoenix landing site in 2008. In 2014 a meteorite from Mars (EETA79001) has been investigated. When investigating this meteorite, it had been concluded that the soil composition was Mars origin because those substances have been detected within the meteorite that is difficult to reconcile with terrestrial contamination. EETA79001 showed the presence of 0.6 ± 0.1 ppm ClO4-, 1.4 ± 0.1 ppm ClO3- and 16 ± 0.2 ppm NO3-. It has been said that because of ClO3-, ClO2- or ClO- should also be presented. This was then produced by Cl- and γ- and X-ray radiolysis of ClO4-.

Furthermore, an article was found comparing the findings on Mars and Antarctic Dry Valley soils. The article includes tables including the concentrations of certain ions found in each place. It has been concluded that the salts of the Phoenix landing site and the salts of the meteorite are similar and that the ADV are also a good match. This also strengthens the argument that ADV is a good Mars analog environment of Earth. The occurring ions and concentrations of it in ADV and on Mars are the same within one order of magnitude. ClO4¬- is three orders of magnitude bigger on Mars than on Earth. NO3- is may be present on Mars but this is at a level below the detection limit of the nitrate sensor. The soil of the meteorite and on the Phoenix landing site are alike, however, on average the concentrations in the meteorite are 4% of those on the Phoenix site and the concentration Ca+ is 16% bigger on the meteorite

The last article includes information about the nitrogen cycle and the ratio of the loss of nitrogen isotopes. This mainly has to do with the air activity, therefore, not relevant for the piece of text about the ground. There was a good explanation, however, why it is difficult to detect nitrate on Mars. This explanation is given below. A cause could be leaching. This means that the nitrate will be at a bigger depth in comparison to less soluble ions such as sulfates.

Nitrates on Mars?

Some articles say the opposite of one another. Some state that nitrate has been detected on Mars and others do not. As nitrate is crucial for growing crops, it is essential to know whether there is actually nitrate on Mars. Because of the fact that all articles are reliable and some are even produced in the same sort of magazine, it has been decided to trust the articles which are more recently made. It could namely be the case that nitrate has not been discovered in 2001 but in between 2001 and 2013 for example. When trusting the most recent article, nitrate has been discovered on Mars.

What is in Martian soil

Several investigations have been taken place in order to find out what substances are located in the soil on Mars. First of all, the Phoenix Mars Lander WCL soil has been analysed and the Mars meteorite EETA79001 sawdust. These type of soils have been compared to soil on the Antarctic Dry Valley and to a Mars simulant. This research is about being able to grow crops (potato’s) on Mars. In order to succeed into this, the easiest way would be to do experiments with the ground which is available on Earth. This is the reason why the Martian soil has been compared to soil on Earth. To be able to grow crops, the soil should be fertile and the amount of fertilizer must be known. What is in the fertilizer and the amount of is needed, is based on the composition of the soil and the needs of a certain crop (in this case the potato). In the table below, the concentration of ions is given for the meteorite and Phoenix Landing soil. 1 gram of soil was added to 25 mL of DI water.

Ionic species	Phoenix WCL mars (μM)	EETA79001 Meteorite (μM)
Ca2+	600 ± 300	1180 ± 1
Cl-	470 ± 90	13.2 ± 0.8
K+	390 ± 80	1.8 ± 0.5
Mg2+	3300 ± 1700	136 ± 1
Na+	1400 ± 300	110 ± 1
NH4+	ND	62 ± 2
NO3-	<1000	48.5 ± 2.5
SO42-	5400 ± 800	117 ± 5
ClO4-	2400 ± 500	1.02 ± 0.11

It has already been concluded that both of these soils are comparative for the Martian soil. It has not yet been decided which soil to take as a representative. Because of the fact that the numbers for what a potato needs are in grams, the amount of μM has to be converted into grams. In the table below, the amount of grams for each ion is given within 1 gram of soil.

Ionic species	gram per gram soil (Phoenix)	gram per gram soil (Meteorite)
Ca2+	6,01E-04	1,18E-03
Cl-	4,17E-04	1,17E-05
K+	3,81E-04	1,76E-06
Mg2+	2,01E-03	8,26E-05
Na+	8,05E-04	6,32E-05
NH4+	0,00E+00	2,79E-05
NO3-	0,00E+00	7,52E-05
SO42-	1,30E-02	2,81E-04
ClO4-	5,97E-03	2,54E-06

In reality, each potato has access to a certain amount soil. The potato is placed in the ground at a depth of 10 cm. The space between the potatoes in the same row is 28 cm and the distance between potatoes in different rows is 75 cm. These numbers have been taken into account in order to calculate the volume of the soil that each potato is able to use. By taken the density of the Martian soil into account, the amount of grams for each ion can be calculated. The results are shown in the table below.

Ionic species	gram total (Phoenix)	gram total (Meteorite)
Ca2+	1,26E+01	2,48E+01
Cl-	8,75E+00	2,46E-01
K+	8,01E+00	3,69E-02
Mg2+	4,21E+01	1,74E+00
Na+	1,69E+01	1,33E+00
NH4+	0,00E+00	5,87E-01
NO3-	0,00E+00	1,58E+00
SO42-	2,72E+02	5,90E+00
ClO4-	1,25E+02	5,33E-02

From the information above can be concluded that the Martian soil contains to less substances for the potatoes to grow on, therefore, the ground needs to be fertilized. The problem with fertilization on Mars is that there are no fertilizer. To this a solution has been found. The 20 people who are going to Mars should produce the fertilizers themselves. This means that these people should use their own feces and pee to fertilize the ground.

Fertilization on Mars

As told above, human feces and pee could be used in order to fertilize the ground. Human feces and pee, however, contain bacteria and parasites which can cause diseases to humans when using it. When sterilizing the feces and pee, this will not be a problem anymore. Since Mars has temperatures that could have a value of -50°C or even -100°C, this can be perfectly sterilized. The sterilization can take place outside and, therefore, being exposed to the cosmetic radiation. This type of radiation will be capable of killing these bacteria and parasites together with the cold. According to Wamelink, when these humans preserve their feces and pee for half a year on earth as a starting package, this should be enough to fertilize the potatoes together with the pee and feces gathered on Mars itself. This also shows that a closed system will be used on Mars, meaning that everything will be used again. The ureum from the pee will be used for fertilizing the ground and the water will be used for drinking. The dead plants will also be used as fertilizers.
When looking at the ground structure of the Martian ground, it has sharp edges and water and oxygen cannot reach deep enough to be picked up by the plants. This means that worms should be used. They can create holes in the ground structure to let more oxygen and water into the ground. It has been tested already by Wamelink that the worms do not die because of the sharp edges in the Martian soil. Furthermore, they have enough food from the ground and the dead plants.
There has already been an experiment carried out by Wamelink to see whether potatoes can grow in Martian soil in a green house. Potatoes indeed grew, however, they faced one main problem. The potatoes kept growing instead of dying. This created a lot of leaves and bad potatoes. The main cause according to Wamelink was that in the greenhouse there were no different seasons created for the plants to die. This induces that in our greenhouse we should try to implement different seasons for an optimal result. These includes varying the length of a day and the temperature smoothly.

Surface area of the field of potatoes

A look will be taken at the amount of surface area which is needed for the potatoes to grow on. According to Wamelink, we could assume that a potato plant has a yield of around 2 kilogram. Each plant needs a surface area of around 50 cm by 50 cm. Each man consumes 250 grams of potatoes for a meal and a female 200 grams. This indicates that on average, 225 grams of potatoes will be eaten by each person for each meal. According to Wamelink, the process of the potatoes will endure three months. So, humans will need potatoes for around 92 days. The amount of potatoes consumed by the people each day is 4,5 kg in total. The amount of kg potatoes needed for those three months is 414. As each plant produces roughly 2 kg of potatoes, 207 plants are needed. As each one will need a space of 50 cm in width and in length, the total area of the field will be equal to 0.50 m * 0.50 m * 270 = 51.75 m²
After a days of eating potatoes, the users might not be satisfied anymore. Taking this into account, future research could also be done on trying to plant wheat on Mars to make pasta for example. In this project, however, we limit ourselves to the potatoes. In the future, one could also take a look at other crops to grow on Mars.

Gravity influence on Mars

Some questions arose whether the gravity on Mars has a significant influence on the development of the potatoes. The answer to this is that no one really knows. The plants do grow when there is a change of gravity, however, their form is not known. In the model we will assume that it has no influence, also because some researcher including Wamelink think that it does not have an influence.

Air on Mars

The atmosphere of mars is composed of 96% CO₂, 1,9% argon, 1,9% nitrogen, 0,15% oxygen and 0,05% CO. Below we will discuss the important compositions. These conditions are far from optimal for the growth of potatoes, and thus we have to create a non-hostile environment for the potatoes to grow. We are going to achieve this by making a friendly environment in a greenhouse. What this friendly environment entails will be described below.

CO₂

The CO₂ level in air on Earth is about 401 ppm (0.00401 %) in which potatoes can grow well. But to get to know if potatoes can grow better in atmospheres with more CO₂, tests using FACE rings are done. A FACE ring is a ring of pipes around a field of crops which emits CO₂ so that the CO₂ values around the crops rise and measurements with different levels of CO₂ can be done. With the outcomes of these experiments it can be concluded that when the CO₂ levels are raised to 660 ppm (0.00660 %) the Leaf Area will decrease, but the activity of the photosynthesis is raised and therefore the number of tubers will increase. While the number of tubers increased, the size and weight of the tubers remained the same as on Earth. With these values in mind it would be a good idea to make an atmosphere in the greenhouse on Mars that has a CO₂ value of 660 ppm (0.00660 %), to make the tuber yield higher and thus create more food from the same amount of crops.

O₂

When potato plants are just planted they will use a lot of O₂, and thus emit a lot of CO₂, to gain energy to make the stems and leaves to be able to start the photosynthesis. It is thus necessary that there is enough O₂ available to the plants to grow at first, but when they are fully grown they will start to transfer CO₂ to O₂. Plants transform CO₂ in O₂ using the energy that they gain from light via photosynthesis, but when there is no light the plants will start respiration. Plants do always convert the glucose that is made with the energy of light to CO₂, water and energy for the plant to keep living, this is called respiration. But when there is not enough light, photosynthesis rate equals or is lower than this respiration rate.

What nutrients does a potato need

Potatos need the following substances in order to develop themselves and grow.

Macronutrients

• Nitrogen (N)
• Phosphate (P)
• Potassium (K)
• Calcium (Ca)
• Magnesium (Mg)
• Sulfur (S)

Micronutrients

• Boron (B)
• Copper (Cu)
• Molybdenum (Mo)
• Iron (Fe)
• Magnanese (Mn)
• Zinc (Zn)

In order to make sure the potatoes receive these substances, human faeces and pee will be used, which will be discussed later on in the report. The macronutrients are the most important nutrients, however, it can also be assumed that there will be enough of the Magnesium and Sulfur when the other nutrients are present in sufficient concentrations. The same goes for all of the micronutrients: when there is enough of the four left-over substances, there will also be enough of the micronutrients. The amount needed of each of these four important substances needs to be calculated. It could happen that there is a surplus of one of the ions. This should not cause any problems to the potatoes, they simply do not absorb the extra ions.
Each of these four important ions will be explained when there is a shortage of it for the potato plant.
Nitrogen: Nitrogen is important for the development of the plant and ensures a better yield. When there is too less of this substance the leaves will not fully grow and a light green decolouration will be seen on the leaves.
Phosphate: Phosphate boosts the development of the tubers and it enlarges the amount of the tubers. It also ensures that the tubers are equally big. This substance actually improves everything that has to do with the tubers. When there is a shortage of it, the growth will be hindered. A shortage of Phosphate can be noticed, because the cuttings will stand up and the colour of the leave will be glazed and dark green. Furthermore, the edges of the leaves will curl up.
Potassium: This is a very important substance. It improves the yield and its quality. Furthermore, the resistance against diseases will increase and the tuber magnitude will increase. When a shortage occurs, the plant growth will be oriented downwards and incomplete. The shortage can be noticed in the leaves as the underside is yellowing and the edges also curl up.
Calcium: A green and healthy leaf will exist because of Calcium. It ensures a better yield and quality. Furthermore, there will be less eruption during the storage of the tubers. A lack of Calcium causes internal scald and hollow tubers.

How much do potatoes need of the fertilizer?

As can be deducted from the piece of text on the mArtina soil, this soil does not contain a concentration of ions which is big enough for the planting of potatoes. It is assumed as if the Martian soil contains nothing and that everything needs to be present in the fertilizer.
In the development and growth of the potato, there are certain stages where the potatoes needs more substances than in other stages. Futhermore, there is a differences between the amount that the tubers need and the plants. In the tabel below, the amount of the four important ions needed each day is given in mg.

	0-15	15-30	30-45	45-60	60-75	75-90
P	3	46	Ca	Mg
Cel 4	Cel 5	Cel 6

Each row represents a certain substance and each column represents a certain stage in the cycle, each one covering a period of 15 days. The amounts given are needed everyday for each plant.

Farming robots

Several articles were found on farming robotics. However most of these articles focus on robots that are (partially) manually controlled. It has only been a couple of years since designing and experimenting with fully autonomous farming robots has begun. The hardest part in programming the robots is to make them able to see whether a fruit or vegetable is ripe, or even to tell apart a fruit or vegetable from the plant. Furthermore the robot needs to be very delicate in order for the plant not to be damaged.

In one of the found articles a robot is described that is used to farm tomatoes. In this case colour is used as a measure of how ripe the tomato is. When the colour is above a certain teint, the robot takes it. Otherwise it waits till the tomato gets a darker shade. The robot described, is a very small robot which climbs up the plant and cuts the stem of the tomato if it is ready. This technique is however very hard to apply in our case, since we want to focus on potatoes which grow under the ground. Though there might be a way to use colour underground if we introduce a light in our robot. Another downside to this technique is that it requires a lot of these small robots, which can turn out to be expensive. On the positive side, these obots are very precise and do not waste a lot of vegetables (once the programming is perfected). An adjustment can be made from looking at the colour by looking for example at the size when it comes to potatoes.

Another article describes how a prototype is built of a fully autonomous harvesting tractor. This is used for vegetables which grow underground, but it is a very blunt device. It basically pulls out everything, including the potatoes that might not be ripe yet. In a very restricted area like Mars this is not desirable, since there are limited supplies and every potato counts.

Also a very useful article was found on how the ideal farming robot could be designed.

Potato research

The book “Introduction to potato production” gives an overview of the entire potato production process.

From the sources, it is clear that there are many factors that decide the size of the tuber yield. These factors include the breed of the potato and also the day length as well as the light intensity. The tuber growth is more delayed as the light intensity decreases (while the haulm growth is stimulated).

It is known that as the light intensity decreases, the tuber growth also decreases, but the growth of the haulm is stimulated.

There are two kinds of potato breeds, these are “long cycle” and “short cycle” potatoes, The short cycle potatoes start growing tubers earlier than the long cycle potatoes, but the long cycle potatoes will outgrow the short cycle ones in the long run. These tubers will become larger.

Some potato breeds do not grow tubers when the day is long, every breed has its own “critical day length” it is thus important that potatoes get a day cycle. The sugar content in the tuber is also dependent of the day length.

From the potato related sources it is also clear what the nutritional requirements are for potatoes per hectare, all these quantities are stated in “nutritional requirements for potatoes”.

Stages of growth

The potato plant grows in certain stages, these are: dormancy (here the plant is not yet growing), sprout growth, emergence (haulm growth), tuber growth. These last three stages do overlap and it is strongly dependent of the breed and the circumstances when these stages are initiated and when these end.

Surface temperature

The ideal soil temperature for potatoes is around 15-18 degrees Celsius.

Ground moisture

During planting, the potato prefers to be wet. After planting, it is important that the ground is kept moist until emergence. In the stage after emergence it is important that the moisture of the ground does not exceed a soil water tension of -0.3 MPa, for then the elongation of the leafs during haulm growth is delayed. The soil water tension is the pressure needed by the plant to extract the water from the ground. It is very important that there is no over-irrigation in this stage of crop growth, as the roots of the plant become superficial, whereas long developed roots are important for later stages. For now the ideal water content in the ground is 65% ASW. ASW (available water content) is the percentage of the maximum amount of water a plant can possibly consume from a certain volume of soil. When the tuber growth initiates, it is important that the ground moisture is sufficient and not inconsistent. It is not possible to know when the soil water content is 65% ASW. Therefore the soil water tension taken into account. The ideal water tension for potatoes can range from -20 to -60 kPa depending on the ground used to grow on, climate of location of growth and the irrigation system used.

Literature search

To start of our project we are doing a literature research. We divided the literature search into the following areas:

1) The conditions on mars (including the effects on aggro culture due to these conditions)

2) Robots and machinery that are already used in outher space

3) Farming robots that are already being used on earth

For all of these areas papers will be searched and a summary of the overall findings will be given with refrences to the found papers.

Mars conditions

- Boersma, H. (2012). Waarom gebruiken we geen mensenpoep als mest? - Kijkmagazine. Retrieved from: https://www.kijkmagazine.nl/nieuws/waarom-gebruiken-we-geen-mensenpoep-als-mest/

- C. Leovy. “Weather and climate on Mars” (2001)

- F. Gifford Jr. “The Surface-Temperature Climate of Mars.” (1955)

- S. R. Lewis, et al. “A climate database for Mars” (1999)

- G.W. Wieger Wamelink, et al. “Can plants grow on mars and the Moon: A growth experiment on Mars and Moon soil simulants” (2014)

- Mars – Sterren en Planeten (2005-2009). Retrieved from: http://www.worldwidebase.com/science/mars.shtml

- M. Nelson, et al. “Integration of lessons from recent research for “Earth to Mars” life support systems (2006)

- S. Silverstone, et al. “Development and research program for a soil-based bioregenerative agriculture system to feed a four person crew at a mars base” (2003)

- Journal of Climate. Jun2001, Vol. 14 Issue 11, p2430. 13p. 23 Graphs..... no access

- Agriculture, Ecosystems & Environment. Feb2018, Vol. 254, p99-110. 12p....... no access

- Climate Research. 2009, Vol. 39 Issue 1, p47-59. 13p. 7 Charts, 5 Graphs, 1 Map..... no access

- Canadian Journal of Forest Research. Oct2010, Vol. 40 Issue 10, p2036-2048. 12p. 1 Chart, 1 Graph..... no accesss

- Global Change Biology. Jan2007, Vol. 13 Issue 1, p169-183. 15p. 1 Diagram, 7 Graphs, 2 Maps..... (no access)

- James I. L. Morison,Michael D. "plant growth and climate change" (2006)..... (no access)

- R. RötterS.C. van de Geijn. "Climate Change Effects on Plant Growth, Crop Yield and Livestock". pp 651–681 (1999).... (no access)

- Angela T. Moles. "Global patterns in plant height"- Journal of ecology. (2009).... access

- Wamelink, W. (2017). Regenwormen komen tot voortplanting op - WUR. Retrieved from: https://www.wur.nl/nl/nieuws/Regenwormen-komen-tot-voortplanting-op-Marsbodemsimulant.htm

- Wamelink, W. (2017). Varkenspoep als voeding - WUR. Retrieved from: https://weblog.wur.nl/ruimtelandbouw/varkensmest-als-voeding/

Potato

- Aardappel – YARA. Retrieved from: http://www.yara.nl/gewasvoeding/gewassen/aardappel/

- Adam H. Sparks. "Climate change may have limited effect on global risk of potato late blight" - Global change biology (2014).... (no access)

- Bakhtiyor Pulatov. "Modeling climate change impact on potato crop phenology, and risk of frost damage and heat stress in northern Europe"- Agricultural and Forest Meteorology. Pages 281-292. (2015).... (no access)

- D.T. Westermann “Nutritional requirements of potatoes” (2005)

- Van Ittersum, M.K. & Scholte, K. Potato Res (1992) 35: 365. https://doi-org.dianus.libr.tue.nl/10.1007/BF02357593

- H.P. Beukema, D.E. van der Zaag "Introduction to potato production" (1990)

- Pootaardappels – Carel Bouma biologisch poot- en plantgoed (2018). Retrieved from: https://www.biologischpootgoed.nl/teeltadvies-pootaardappelen/

- P.L. Kooman et al. "Effects of climate on different potato genotypes 2. Dry matter allocation and duration of the growth cycle" (1996)

- C.C. Shock, A.B. Pereira, E.P. Eldredge "Irrigation Best Management Practices for Potato" (2007)

Existing farming technology

- Tillet, N. (2003). Robots on the farm. The industrial robot, 30(5), 396. Retrieved February 23, 2018, from [1]

- Giles, F. (2017). Agricultural robots no longer science fiction. Florida grower, 110(2), 12-13. Retrieved February 23, 2018, from [2]

- Hill, P. (2016). 9 robots designed to enhance the farm workforce. Farmers Weekly, 165(3), 66-70,72,75. Retrieved from [3]

- Robert Bogue, (2013) "Can robots help to feed the world?", Industrial Robot: An International Journal, Vol. 40 Issue: 1, pp.4-9, [4]

- Victor Bloch, Avital Bechar, Amir Degani, (2017) "Development of an environment characterization methodology for optimal design of an agricultural robot", Industrial Robot: An International Journal, Vol. 44 Issue: 1, pp.94-103, [5]

- Bac, C. W., van Henten, E. J., Hemming, J. and Edan, Y. (2014), Harvesting Robots for High-value Crops: State-of-the-art Review and Challenges Ahead. J. Field Robotics, 31: 888–911. doi:10.1002/rob.21525

Robots and machinery used in outer space

- Rećko, M., Tołstoj-Sienkiewicz, J., & Turycz, P. (2017). Versatile soil sampling system capable of collecting, transporting, storing and preliminary onboard analysis for mars rover analogue10.4028/www.scientific.net/SSP.260.59 [Robotic arm for Mars Rover] Link to article

- Czaplicki, P., Recko, M., & Tolstoj-Sienkiewicz, J. (2016). Robotic arm control system for mars rover analogue. Paper presented at the 2016 21st International Conference on Methods and Models in Automation and Robotics, MMAR 2016, 1122-1126. 10.1109/MMAR.2016.7575295 [Soil sampling] Link to article

- Sakib, N., Ahmed, Z., Farayez, A., & Kabir, M. H. (2017). An approach to build simplified semi-autonomous mars rover. Paper presented at the IEEE Region 10 Annual International Conference, Proceedings/TENCON, 3502-3505. 10.1109/TENCON.2016.7848707 [Making a Mars Rover semi-automatic] Link to article

- Wong, C., Yang, E., Yan, X. -., & Gu, D. (2017). Adaptive and intelligent navigation of autonomous planetary rovers-A survey. Paper presented at the 2017 NASA/ESA Conference on Adaptive Hardware and Systems, AHS 2017, 237-244. 10.1109/AHS.2017.8046384 [Intelligent navigation] Link to article

- Parness, A., Abcouwer, N., Fuller, C., Wiltsie, N., Nash, J., & Kennedy, B. (2017). LEMUR 3: A limbed climbing robot for extreme terrain mobility in space. Paper presented at the Proceedings - IEEE International Conference on Robotics and Automation, 5467-5473. 10.1109/ICRA.2017.7989643 [Robot with climbing arms (maybe possible to use for planting and harvesting] Link to article

- Garrido, S., Moreno, L., Martín, F., & Álvarez, D. (2017). Fast marching subjected to a vector field–path planning method for mars rovers. Expert Systems with Applications, 78, 334-346. 10.1016/j.eswa.2017.02.019 [Vector field-path planning] Link to article

- Scopus search link

Soil on Mars

- Boynton, W.V. , D. W. Ming, S. P. Kounaves, S. M. M. Young,† R. E. Arvidson, M. H. Hecht, J. Hoffman, P. B. Niles, D. K. Hamara, R. C. Quinn, P. H. Smith, B. Sutter, D. C. Catling, R. V. Morris. (2009). Evidence for Calcium Carbonate at the Mars Phoenix Landing Site – Science

- Hecht M. H. , S. P. Kounaves, R. C. Quinn, S. J. West, S. M. M. Young,† D. W. Ming, D. C. Catling, B. C. Clark, W. V. Boynton, J. Hoffman, L. P. DeFlores, K. Gospodinova, J. Kapit, P. H. Smith. (2009). Detection of Perchlorate and the Soluble Chemistry of Martian Soil at the Phoenix Lander Site – Science.

- Kounaves S. P., Brandi L. Carrier, Glen D. O’Neil, Shannon T. Stroble, Mark W. Claire. (2014). Evidence of martian perchlorate, chlorate, and nitrate in Mars meteorite EETA79001: Implications for oxidants and organics – Icarus.

- Manning C. V. , Christopher P. McKay, Kevin J. Zahnle. (2008) The nitrogen cycle on Mars: Impact decomposition of near-surface nitrates as a source for a nitrogen steady state – Icarus.

- Mustard J.F. , Christopher D. Cooper & Moses K. Rifkin. (2001). Evidence for recent climate change on Mars from the identication of youthful near-surface ground ice – letters to nature.

- Smith M. L., Mark W. Claire, David C. Catling, Kevin J. Zahnle. (2014). The formation of sulfate, nitrate and perchlorate salts in the martian atmosphere – Icarus.

- Stroble S. P., Kyle M. McElhoney, Samuel P. Kounaves. (2013). Comparison of the Phoenix Mars Lander WCL soil analyses with Antarctic Dry Valley soils, Mars meteorite EETA79001 sawdust, and a Mars simulant – Icarus.

Coaching Questions

Coaching Questions Group 1