Chemicals of Europa

As we mentioned at the end of our previous blog post, there are certain chemicals we know Europa would need to have in order for there to be life.

Detection Of Chemicals

At first it may seem strange to be talking about the chemicals of Europa at all. To date, no probes have skimmed the atmosphere of Europa, let alone landed and taken samples for chemical analysis. Yet here you are about to read about the chemicals that are present. This is made possible by of one of the most basic tenets of quantum mechanics, namely the idea that electrons have quantized energy levels. This means that electrons can only exist in certain regions of an atom, with a specific energy inherent to that region. In order to move from one of these energy levels to another an electron must either emit or absorb a photon whose energy is the difference between the energy levels. The energy, and also color of a particular photon is determined by its frequency. Therefore, if you look at the light emitted by a heated substance, you will see distinct bands of colors indicating the electron transitions occurring. What makes this useful for identifying chemicals is that the energy levels that are available to the electrons and the transitions that occur are completely dependent upon the element or compound. Moreover, each unique compound has its own emission and absorption spectra, the features of which can be detected even amongst a whole moon full of chemicals nearly 400 million miles away. This method has discovered the presence of two important chemicals on Europa: oxygen and hydrogen peroxide.

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The Importance of Oxygen and Hydrogen Peroxide

The reason that scientists think that finding evidence of hydrogen peroxide and oxygen on Europa is important is because they are among the best oxidation agents known to exist. Oxidation agents are essential to every form of life that we know exists. They are most important because of their role in redox, or oxidation-reduction, reactions. In a redox reaction one compound takes electrons from another.  The compound that gains the electrons becomes reduced, and the compound that loses the electrons is oxidized. Examples of redox reactions include everything from the rusting of iron (where iron is oxidized and oxygen is reduced) to the reaction between glucose and oxygen.

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Respiration- Both Simple and Complex

Perhaps the most important redox reactions for living organisms are those involved in respiration. Just like all compounds, organic compounds, such as the proteins and carbohydrates that make up organisms, have energy stored in the bonds that hold it together. Taken as a whole, respiration works a lot like combustion, in which a hydrocarbon is oxidized and energy is realized in the form of heat. However, if fires were constantly starting in our mitochondria, we would have some significant problems. Fortunately, the process is broken into many steps, each of which releases a relatively small amount of energy. In complex multicellular life on Earth, this process is done through a series of increasingly powerful oxidizing agents known as the electron transport chain. The electron transport chain transfers electrons from the organic compound being brought down through a series of complex compounds until it ends up being captured by oxygen, the final electron acceptor.

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Water

Perhaps the most important substance for life to exist is liquid water. In the first blog post, we talked about how and why scientists suspect that there is liquid water on Europa. Now we are going to talk about why water in particular is so important.

Polarity

Anyone who knows anything about electronegativity can tell you that water is a polar molecule. The oxygen atom takes on a partial negative charge (denoted 𝛿-) and each of the hydrogen atoms takes on a partial positive charge (denoted 𝛿+). These partial charges allow water to dissolve countless polar and ionic solids, hence why it is referred to as the universal solvent. Most biological reactions will only happen if all of the reactants are in the aqueous state. There is a tendency for polar compounds to dissolve other polar compounds and for non-polar compounds to dissolve other non-polar compounds, and this allows for the easy storage of water. Non-polar molecules like lipids are used to form membranes in cells that are capable of retaining water.

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Water’s efficacy as a solvent is part of why it is so vital to life on Earth. All (known) living organisms contain liquid water in their bodies. Water is used to transport nutrients and other vital substances (e.g. glucose) to the areas of our body in need. Other compounds, such as salts are also transported via water. In most animals, blood forms the primary method of active nutrient transfer in the body, and blood’s ability to transport the nutrients depends on water’s solubility.

Hydrogen Bonding

Because water contains hydrogen atoms bonded to oxygen atoms, it contains in what is called “hydrogen bonds”, the strongest type of intermolecular force. This leads to a series of interesting and important properties of water. For one, each water molecule is strongly attracted to the other water molecules around it, making it hard for water molecules to break away and evaporate into the vapor phase. This gives water a relatively high boiling point (100°C) for such a small molecule. This means that it would take very serious changes in the environment to cause a phase change for large amounts of water. Hydrogen bonding is also responsible for water’s unusual property of having it’s solid phase (ice) be less dense than its liquid phase (water). The optimal bond lengths for the hydrogen bonds are actually greater than the distances water molecules usually are from each other causing them to expand as they freeze. This allows for the phenomenon of underwater oceans to exist because the less dense ice essentially floats on top of the water.  The ice basically thermally insulates the rest of the water from the surrounding freezing conditions. In Europa’s case, the ice acts as an insulating blanket, trapping the internal heat generated by Europa’s movement around Jupiter. This insulated layers allow for the possibility of a liquid ocean existing.

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Future

Future missions to explore Europa, like NASA’s proposed Europa Clipper aim to analyze the surface of Europa. The mission would launch a satellite to orbit Europa, performing repeated close flybys of the moon’s surface. Various scientific instruments would be used to analyze the surface and trace atmospheric composition of Europa. High-resolution cameras would also enable exquisitely detailed surface imaging of Europa’s icy outer layer. Additionally, there exists the possibility for radar to be included on the satellite, which would allow NASA to determine the depth of Europa’s surface ice.

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Will It Go ‘Round in Circles: PAHs

What are PAHs?

PAHs, short for Polycyclic Aromatic Hydrocarbons, are groups of naturally occurring or man-made chemicals that result from the incomplete burning of many fuels such as coal, oil and even gas. When drawn, they look like multiple rings of benzene bonded together to form chains or sheets or… other odd shapes. You’re probably thinking, “How are rings going to hurt me?” Yet they do. They have been linked to cancer and can even hinder reproductive health. Clearly, in our current age and society the abundance of PAHs is potentially much higher than any previous generation. It is also necessary to notice that substances which produce the most PAHs are the compounds with the most moles of Carbon. Other than messing around, PAHs have two primary uses: research and dyes. They are also used to make plastics and pesticides. 

That’s Great, but what do we actually see?

PAHs in their base forms, because they are made of only carbon and hydrogen, are organic molecules and are thus nonpolar. Thus, they barely dissolve in water if at all, but they love to dissolve in fats, oils, and other organic solvents. PAHs are all solids, but their form depends on which method is used to crystallize them–some end up forming needles or plates. Their colors vary: for instance, anthracene is colorless in its purest state, benzo(a)pyrene is pale yellow, and pyrene can be either depending on the method it is crystallized.

 

I Thought Rings Were for Marriage

You’re probably thinking, “Oh, it’s an organic molecule, right? It can’t possibly be bad for me…” Apparently, the only type of rings the body tolerates come in the form of engagement and marriage. The body really doesn’t want PAHs inside. For starters, 200 of them are found in cigarette smoke, and many of these have the ability to hinder reproduction. Then they have the ability to indirectly cause cancer.

Benzo[a]pyrene is one of the worst PAHs there are; its effects have been well documented. Chimney sweeps often found themselves getting scrotal cancer due to this compound–in the mid 19th century. In today’s world, benzo[a]pyrene has been found in cigarette smoke, being one of the molecules that could potentially cause lung cancer, among others, by binding to DNA. In doing so, they may end up interfering with DNA replication. The mechanisms by which the DNA is metabolized are far too complex to be understood here (at least at the high school level for someone who hasn’t done any research), but know this: the body metabolizes it to form its toxic forms. Not only that, but it hampers your immune system. Overall, the body metabolizes benzo[a]pyrene and many other PAHS through microsomal enzymes, forming compounds that bind to DNA and introduce mutations.

And You Might Be Wearing Them Now

Most PAHS lack practical everyday uses, barring that some of them are toxic. Most of them that are used are used for research purposes only. Yet, as previously mentioned, some could be on you right now in your clothing. They were used in the process of making the color. The PAHs that have dyeing abilities include but are not limited to anthracene, carbazole, and pyrene. Anthracene is used to make red dyes, carbazole for violet, and pyrene for fluorescence. This technology has been used for quite a while; the patent for anthracene and its process was filed in 1925. Also, while its status as a PAH is debatable, naphthalene has been found in mothballs, a critical component of clothing storage, though it has been phased out because it has a tendency to catch on fire. But in the more practical sense, PAHs show up in many things derived from coal tars, including asphalt (the stuff cars drive on) and even cosmetics (things you put on your face).

 

And in a way that could actually benefit humanity, some PAHs are implemented into dye-sensitized solar cells. Dyes are used to boost output in otherwise unfavorable conditions while also diminishing costs by eliminating some of the expensive materials used in it. These dyes are often coated on the titanium dioxide found in the solar panel. The dyes can be based off of PAHs, for they give them superb photoconducting skills. For instance, carbazole is made electron-rich due to its nitrogen atom, making it useful for the  electron transfer necessary to induce current. And a dye known as TC501, bridged by anthracene, improved the open-circuit photovoltages and short-circuit photocurrent densities of a dye-sensitized solar cell, so much so that the solar conversion efficiency jumped to 7.03%, which is a relatively remarkable number. Many of the mechanisms by which PAHs assist in photoelectric conversions are specific to that PAH, and some of them are not yet fully understood. And speaking of extraterrestrial energy…

There’s Plenty of Space for This Poison Elsewhere

Naturally, we are able to observe things specifically on the planet Earth, otherwise we need either telescopes or overactive imaginations (we recommend some of both). Using this, science can now tell us that certain molecules also occur outside in the cold, not-empty void of interstellar space. The spectra of PAHs have been found in conjunction with large molecular and dust clouds; it is speculated that they form by photoionisation, which is also what causes hydrogen clouds to form in these places. Photoionisation, as the name may suggest, involves light providing the energy to ionise molecules and cause them to form into compounds. Sounds like a great way to cook

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For those who have an inexplicable fear of deep space, there’s something for you as well. PAHs have also been found in the atmosphere of Titan. Titan, as you should probably be required to know, is Saturn’s largest moon. It’s unique because it is the only moon to maintain a substantive atmosphere. To the average flying robot, it is an orange ball. Titan is a lot closer than all interstellar space, so we can accurately detect what is in the ball of Orange. It turns out that, besides a load of nitrogen (boring), there are PAHs as well. Those that the European Space Agency found are a bit more complex than the ones our beleaguered lungs are most familiar with, but they are still the same sort of molecules. It may be worth adding here that Titan also seems to have surface lakes of hydrocarbons, which may be of similar origin. Seti, or the Search for ExtraTerrestrial Intelligence, has found indications that these molecules, besides being distributed in gas clouds, are also found in interstellar dust and locked up in water ice. These are the basic ingredients in planet formation and by extension that of more complex organic forms.

Good Poison?

You learned earlier that PAHs often result from the burning of organic or fossil-derived materials. The existence of such complex  molecules in both interstellar clouds and the atmosphere of a moon suggest that maybe the molecules related to life are not so rare as we might’ve thought, and it certainly opens some new eyes and avenues for which to explore. Scientists have been forever intrigued by the presumably unique condition of life on the planet Earth. With the discovery of new worlds beyond our solar system, and the recent insights into the conditions on some places a bit closer, perhaps we will discover that, just maybe, we are not alone.

Sustainable Living Conditions in Space

The Cell Respiration Components on Earth

C6H12O6 + 6 O2 + 36 ADP + 36 Pi —-> 6 CO2 + 6 H2O + 36 ATP + heat

       The cell respiration equation is the single most important chemical reaction occurring in the body of any multicellular living thing on Earth. It is the equation that stores energy from glucose molecules in the cell as ATP, the main energy storage in most cells. This ATP is then broken apart into ADP and phosphate to release that energy and do cell work. Cell work is defined as any job a cell performs, whether it be creating a certain material or simply expanding and contracting repeatedly forever. It also powers mitosis, meiosis, and allows the cell to grow.

       However, the equation shown above only applies to a single cell using a single piece of glucose to produce energy. In reality, cells are storing the energy from glucose as ATP constantly, every moment of every day, in every cell in the human body. The millions of cells in a person’s body means that one must carry out the above reaction millions of times, every day. No wonder people eat so much, with all of that glucose they need!

       Even if it’s multiplied for every cell in the human body, the above equation is still a simplification. In reality there are many steps hidden beneath that equation.

  1. Glucose – The only outside product that the cell requires to do work, glucose is the most basic sugar the body can process. The C6H12O6 portion of the equation, glucose stores a lot of energy within its bonds. It undergoes a process called glycolysis within the cytoplasm of the cell that turns glucose into pyruvate that can be further processed and used to make extra ATP, turn NAD into NADH, or turn FADH into FADH2. Glycolysis by itself generates 4 ATP but requires 2 ATP to start the process, resulting in a net gain of 2 ATP. Glucose is created by the body during digestion, when it breaks down more complex starches and sugars into the more simple glucose molecule that cells can process.

  2. Oxygen – The 6O2 term of the product side of the equation, oxygen is required during the stage of respiration called oxidative phosphorylation. This stage uses a series of redox reactions to transfer electrons from electron donors within the mitochondria of the cell to the oxygen, releasing energy that is used to create ATP. This is known as the electron transport chain, as it transports electrons from the donors to the oxygen. This eventually becomes CO2 and can be found in plentiful quantities in Earth’s atmosphere. Acquiring enough oxygen for cell respiration is as simple as breathing in.

  3. ADP and Pi – ADP and Pi are two components of ATP. ADP stands for adenosine diphosphate. It is comprised of two main components, the adenosine base and the phosphate tail. As it is diphosphate, it has two phosphates in its tail. While not generally done in normal cell respiration, these phosphates can be broken off to release some energy and produce AP, or adenosine phosphate, which only has one phosphate on its tail. The Pi in the equation stands for the inorganic phosphates that are being attached to the ADP throughout the process of cell respiration. Both ADP and phosphate are recycled in the cell meaning it is never created nor destroyed.

  4. ATP – The main product of the cell respiration equation is adenosine triphosphate or ATP. The main energy carrier of the cell, ATP is made up of an adenosine base and a phosphate tail containing three phosphate groups. The third phosphate group is what is broken off when the cell requires energy to do work. Throughout the entire process of cell respiration, 38 total ATP are created and 2 ATP are used, resulting in a net gain of 36 ATP from a single molecule of glucose. Like ADP and phosphate, it is recycled in the cell until it dies.

  5. CO2 – A waste product of cell respiration, CO2 is inert by itself, but can suffocate cells in large quantities. The body needs to get rid of the CO2 generated by cell respiration, and does that whenever one breathes out.

2.     The Equation Components for Earth Orbit in the ISS

       The two issues space engineers have for designing a permanent orbital station such as the ISS is filtering of carbon dioxide, production of oxygen, and how to supply glucose. Supplying glucose to the astronauts in the space station is relatively easy, if expensive. Every shuttle that goes up to the station to change out the crew is also packed with supplies for the astronauts until the next shuttle goes up. This is much more expensive than supplying the ISS with a renewable food source, but much less complicated and leaves room for more scientific equipment and living quarters on the space station.

       However, this still leaves the somewhat more complex issues of carbon dioxide filtration and oxygen production. While these two may seem to go hand in hand, they actually require very different systems to accomplish.

  1. Carbon Dioxide Scrubbing – Carbon dioxide buildup is one of the main hazards for the International Space Station. With up to eight astronauts living and working in the station at the same time, it can happen quickly if special precautions and advanced filtration systems aren’t used to remove the waste gas.

    1. Trace Contaminant Control Assembly – Air first passes through the Trace Contaminant Control Assembly on its way to the carbon dioxide removal system. As its name suggests, the TCCA removes any trace amounts of potentially harmful substances, such as gas and vapors from lab experiments. If these were left to accumulate, it could cause permanent damage to the station or the astronauts.

    2. Temperature and Humidity Control – The Temperature and Humidity Control system’s function is also obvious. It circulates air constantly, allowing water to condense and bringing the temperature to a constant level for recirculation through the system.

    3. Carbon Dioxide Removal and Overboard Venting – After having the water removed for recirculation through the station, the dry air is sent to Carbon Dioxide Removal. The CO2removal system on the ISS involves a regenerable metal-oxide removal system, which uses a metal oxide to absorb the carbon dioxide from the air. Extremely hot air has to be pumped through the system to activate the regeneration system and regenerate the oxide. Carbon dioxide collected in this way is then vented overboard.

  2. Oxygen Generation (See Fig. 3)

    1. Carbon dioxide removal is not enough to support life, oxygen has to be present as well. The Oxygen Generation system on the ISS was created to do just that. Before the current systems were implemented, the ISS used to get oxygen from the remaining oxidizer present in the space shuttles that brought astronauts to and from the station. The new generation system allows the ISS to go longer without oxygen refueling from a shuttle. The only requirement for the stations generation system is water and electricity. The water collected earlier from the Temp and Humidity Control systems is hydrolyzed into hydrogen and oxygen. The oxygen is pumped throughout the ISS and the excess hydrogen is vented overboard.

  3. Water

    1. Water only appears in the cell respiration equation on the products side, but still has to be considered when sending astronauts into space. Water is not only important for drinking, but it generates the oxygen required for the astronauts to continue living. Water on the ISS is both recycled and generated by the systems on the station. The fuel cells of the ISS that use electrolysis to combine oxygen and hydrogen into water and electricity generates drinkable water for the astronauts to use, as well as the energy that keeps the station running. Water is also kept track of meticulously, with every ounce that the astronauts waste from their body collected and filtered. The water collected in the Temp and Humidity control system is sent directly to Potable Water Processing which sanitizes it and brings it to a constant temperature. Urine is also collected and heavily filtered throughout the station in the same system. This sanitized water is sent to the oxygen generation system, as well as any other systems that require water such as showers, hand washing, and drinking water dispensers.

    2. Electrolysis is the decomposition of water (H2O) into Oxygen (O2) and Hydrogen gas (H2) by passing an electric current through it. This is done by attaching a power source to two electrodes, or plates that are placed in water. Hydrogen appears on the cathode, or negatively charged plate, while the oxygen will appear on the anode, or the positively charged plate. The plates ‘attract’ different particles because of the two different reactions involved within Electrolysis: Reduction and Oxidation

      1. Oxidation involves the loss of electrons overall. Because of this, it takes place at the positive electrode, the anode, due to the lack of electrons on it. This half reaction is: 2 H2O(l) → O2(g) + 4 H+(aq) + 4e−.  In this reaction, the liquid water is electrolyzed resulting in Oxygen gas, and aqueous H+ ions. The electrons are put through the battery into the cathode bar.

      2. Reduction involves the gain of electrons. By gaining the electrons lost in the oxidation reaction at the anode, we have the half reaction: 2 H2O(l) + 2e− → H2(g) + 2 OH-(aq).  In this, electrons are added to liquid water to create hydrogen gas and OH-.

      3. These reactions put together simplify into the overall reaction of 2 H2O(l) → 2 H2(g) + O2(g). The H+ and OH- ions are joined back into liquid water, and put back into the equation. Then, the gaseous oxygen and hydrogen are captured and used as needed.

Simple Electrolysis demonstrationAtoms in the Chemical Equation

       All of these systems have to be specialized, protected, transported, and maintained by the countries part of the ISS program. This tends to get extremely costly, inefficient for a single-use ship. As the ISS is a more permanent fixture of the night sky, the cost becomes less and the benefits become greater.

3.     Is it Worth the Effort and Cost?

As it is so expensive to send astronauts up in the first place, is space travel really worth it anymore? Many people would argue that it isn’t without accomplishing anything new. The truth is, humanity has a lot to learn about space and space travel still and the International Space Station is perfectly equipped to help humans learn these things.

  • Effects of Staying in Space for Years

    • Travelling to far-off planets such as Mars could take up to a year of space travel. Permanent space stations such as the ISS have the systems and supplies needed to research the effects of low-gravity, cosmic radiation, and confined spaces on a human for that kind of time. To bring humanity to Mars, and eventually the stars, systems for keeping humans in space without any contact from the outside world for months or years at a time are required.

  • Spare Repairmen

    • The Global Positioning System, a huge network of satellites in orbit all across the Earth, occasionally requires maintenance that cannot be done remotely. A stable “repair crew” for satellites that lived in a space station, even one in low-Earth orbit, would be more efficient than sending shuttle after shuttle to repair them when damaged. While the initial setup would be expensive, as well as the systems required to keep them alive while in space, the cost over time would be extremely small compared to sending up repeated shuttles. The same goes for non-satellites in orbit as well, such as the Hubble Space Telescope.

  • Increased Research Potential

    • The atmosphere, the great sphere of gases that sustains life and protects us from the harmful radiation of the sun’s light, is an astrophysicist’s worst nightmare. It scatters light and radiation in all directions, making pictures of space in all spectrums of light blurry and distorted. The Hubble Space Telescope, one of the most famous telescopes in existence, was a huge leap forward as it allowed scientists to see clearly without the scattering effect of the atmosphere. Sending a crew of astrophysicists and astronauts into space in a similar fashion and leaving them there to collect data would be invaluable in understanding the universe.