X-ray Diffraction Used by Curiosiy

As we talk about space and the chemistry of foreign bodies millions of miles from Earth, it seems silly not to discuss one of the most important aspects regarding the analysis of such data; the retrieval of samples. Presently there are probes traveling through space gathering data and sending it back to Earth, such as the New Horizons Probe, which was launched by NASA in 2006 and is expected to pass Pluto in July 2015, as well as rovers on Mars, such as the Mars Opportunity Rover, which was launched in 2003 and has already trekked 20 miles.

Mars Opportunity Rover

Currently, there is a new rover on Mars, called the Curiosity Rover. It was this rover that created so much hype as it descended successfully onto the Martian surface on August 6th. This rover is set apart from previous rovers for its sophisticated on board sample analysis system. Through such instruments, it is possible for the rover to send important data back to Earth. One of the most important equipment on Curiosity is a spectrometer called the Chemistry and Mineralogy instrument, or Chemin for short. It is about the size of a laptop computer inside a carrying case and it measures the abundances of various minerals of Mars, which are indicative of environmental conditions that existed when they formed. 

As the gif demonstrates, Chemin performs X-ray diffraction measurements. It fires thin beams of X-rays through powdered material gathered by Curiosity. Some of the X-rays get absorbed by the atoms in the sample and then re-emitted at energies that are specifically characteristic of the particular atoms present in the sample. X-rays can also bounce away at a certain angle that corresponds to the internal crystalline structure of the sample. Measuring this angle which which the X-rays are diffracted into the detector can identify the minerals.

The image above is the X-ray diffraction results produced by Chemin which is sent back to Earth. The diffraction signals are the rings that represent the fingerprint of the minerals. The rings provides information on both what minerals are present as well as how abundant they are. 

And Chemin is only one piece of equipment on the Curiosity Rover. There are also cameras, radiation detectors, environmental sensors, and atmospheric sensors. Weighing one ton, more than any other rover made, the Curiosity Rover truly deserves the name Mars Science Laboratory. 

The Significance of Saturn to Past Civilizations

When we think about the planets, we think of these massive extraterrestrial objects that just happen to be in our solar system, revolving around the sun just like the Earth does. These planets have an atmosphere of their own, are made up of different materials, can be ridiculously far away, and some possibly have the means to support life. But to people years and years ago, the planets meant so much more. These planets were so magnificent in their structure and so far away because they were not simple objects in the skies. The planets we commonly see in a textbook were to them the Gods that control the universe and everything in it.

Zeus in his fight with Cronus. 

In Greek mythology, Saturn is the all powerful being Cronus, who was the father of Zeus (Jupiter). Cronus was the head of the throne over all the other Gods in the universe. However, to prevent being dethroned, Cronus ate his children. Zeus ends up overpowering Cronus, puts him in chains, and banishes him completely.


In Egyptian mythology, the story plays out a little differently. Saturn was the God Osiris. Osiris is murdered and completely dismembered by his brother Seth. Osiris' wife Isis (who was Jupiter) is able to collect all of the dispersed parts, and puts them into a swathing. Osiris' body is restored and he is brought back to life, becoming the king of the Underworld. Isis conceives a baby with Osiris named Horus, who fights Seth to avenge his father's death. 

The standoff between Horus and Seth 

In both of these situations, Saturn is portrayed as an amazing God who ends up losing his power forever. Saturn is then put into the shadow of another being like Jupiter. Maybe when civilizations saw Saturn, they were captivated by its rings and named it to be the almighty God instead of other planets. Maybe when past civilizations were around, they were easily able to see Saturn, but as years went by, Jupiter became the more common sight. Regardless of the reason, the beliefs of these cultures show how amazing these objects in the sky were to them, and how prevalent they were to their daily lives.

Like Dissolves Like Millions of Miles Away

One of the main reasons scientists study space is to find signs of life on other celestial bodies. This is also the basis for why Mars gets so much attention. Out of all the celestial bodies known to us, it is the one most likely to contain life. The reason why Mars has the possibility of containing life is that it has a strong possibility of having water on its surface. Water is considered the most essential part for life to exist for a few reasons. For one, every organism on Earth needs water to survive. Another reason is that all of the organic compounds that make of living things work well with water.

This makes sense because most of the organic compounds that are necessary for life are polar, such as glucose. Even some of the compounds that are not polar have high molar masses. Due to their high molar mass, these compounds have large London Dispersion Forces (LDF). Solubility of molecules depends on their intermolecular forces (IMF). Solvents with high IMFs dissolve solutes with high IMFs and vice versa; this is the “like dissolves like” rule. This why water, a polar molecule, can dissolve all of the organic compounds that organisms need to break down for food. What if organisms used compounds and solvents with lower IMFs?

New research about Titan, Saturn’s moon, proposes this same theory. Titan contains liquid and gaseous methane in its atmosphere and on parts of its surface. Scientist proposed a theory stating that there is a possibility that organisms on Titan could use methane as their organic solvent instead of water. Since methane is nonpolar and has a low LDF, compounds that are nonpolar and have low LDFs would be needed for the methane to be useful. Acetylene is a compound that scientist believe could be used in place on glucose if this theory were proven true. Since, this follows the “like dissolves like” rule, this concept is quite plausible.

Does the type of ice even matter?

Unlike what many people believe, Mars is actually very similar to Earth. Mars also have polar ice caps, which get bigger and smaller in accordance to the seasons. These seasonal polar caps are made from the martian air that freezes during the winter. They are made out of frozen carbon dioxide, or "dry ice." So why are these caps made out of carbon dioxide? Why not water?

Answering this question seems very simple. For one thing, the atmosphere of Mars is 95 percent carbon dioxide. That means that when the air freezes during the winter, the gaseous carbon dioxide is converted in solid carbon dioxide and stored in the polar caps. Depending on the time of year, more than a quarter of the atmosphere can be found frozen on the ground in these caps. 

But is that really the only answer? We can dive a little deeper into chemistry to fully answer this question. 

Carbon dioxide has a low boiling point. This is because the only intermolecular force in carbon dioxide is London Dispersion Forces, or LDF. It does not have dipole dipole interactions because of the structure's symmetry, nor hydrogen bonding, because it is a nonpolar molecule. Therefore, it does not require much energy to separate carbon dioxide molecules from the solid state to gas state. It would take low amounts of energy and low temperatures to have dry ice, and these measurements are found conveniently on Mars.

Maybe you already knew that carbon dioxide has only low LDF. But did you ever think to connect that simple idea to the polar ice cap cycle existing on Mars? These simple connections can easily be made, if you just look for them throughout the universe. 

Atmosphere of Saturn

If you look across the skyline of American cities, this sight is not very uncommon. It seems like there is smoke coming out of these buildings, corporations, and factories. After all, they are called smokestacks. In fact, you would not be too far off to say that this is smoke. Smoke is a collection of tiny solid, liquid, and gas particles. But what you see in this picture is a specific form of smoke known as smog. Smog might not be as familiar to the average person. 

This cycle shows how smog is produced

Smog is created by the many pollutants in our atmosphere creating ozone, and reacting with light. Refineries, factories, chemical plants, and the burning of fossil fuels for car engines produces volatile organic compounds like acetone, benzene, formaldehyde, etc. , sulfur. and nitrogen oxides. This in turn makes ozone. While we regularly hear of ozone as the layer in the atmosphere protecting the earth from the ultraviolet rays of the sun, ground level ozone can be quite dangerous. The ground level ozone can be the cause of breathing problems, asthma, reduced resistance to lung infections and colds, and eye irritation. It can even inhibit plant growth and cause terrible damage to crops and forests. Smog is most visible as the morning haze we sometimes might see in the morning or "smoke and fog". 

An actual picture of Saturn

We know that tons and tons of pollutants are being released into the atmosphere, but a lot of the time don't even bother to think twice about it. Well here is a simple reason why we should put a lot more focus on the way we treat Earth: The picture above is a picture of Saturn. One of the first questions you might have is why Saturn is such a weird color? While Earth is approximately 79% Nitrogen and 21% Oxygen, Saturn is 75% Hydrogen and 25% Helium. But in the atmosphere of Saturn there are trace amounts of nitrogen, oxygen, and sulfur. Why is this such a big deal? Surrounding Saturn is a layer of smog! Even with such small amounts of nitrogen, oxygen, and sulfur, the majority of the planet is covered in a film of it. It is almost scary to think that a layer of this nasty gunk is slowly building up on Earth and might destroy the beautiful blues and greens we think of when we look at a picture of Earth. Looking back at the picture at the top, a grayish Earth just might already be here...

The Atmosphere of Mars

The atmosphere of planets is an important variable that drastically affects the surfaces. For example, since the atmosphere of Venus is so thick, Venus is a barren and burning planet. The Earth's atmosphere is a vital factor to life on earth. Neptune is blue because of the composition of its atmosphere, mostly methane, and has storms up to 2,400 km/hr, the fastest winds in out of all the planets.

The Planets and Pluto. Not to scale.

Mars in particular has a thin atmosphere. It is 100 times thinner than that of Earth and composed of 95.3 percent carbon dioxide, 2.7 percent nitrogen, 1.6 percent argon, .13 percent oxygen, and .08 percent carbon monoxide, with trace amounts of water, nitrogen oxide, neon, hydrogen-deuterium-oxygen, krypton and xenon. The atmosphere is thick enough to support weather, clouds, and winds. Seasonally, the density of the atmosphere changes because the carbon dioxide freezes out of the air in the winter. Mars also has the largest dust storms in the solar system, capable of blanketing the entire planet for months. These dust storms occur because the airborne dust absorbs sunlight, which warms the surrounding atmosphere, causing warmers air to flow to colder regions, generating winds; gradually strong winds lift dust off the ground, creating huge dust storms.

Two images taken by the Hubble Space Telescope showing Mars before (left) and during (right) the great Martian dust storm of 2001. 

Some scientists believe that at one point in history, Mars had a thicker atmosphere, cloudy skies, and liquid water flowing on the surface. But then, throughout its history, a process called sputtering would have knocked away atoms from its atmosphere through impacts from energetic particles. This video explains the process. 

It is interesting to see that while Mars and Earth look drastically different, in the past Mars might have just been like the Earth of the present, capable of housing life. This is what the hopes of many scientists lie on, the chance that Mars will once again be able to house life. While it might seem like a scene straight out of a sci-fi movie, life on mars might not be in the too distant future. 

The Soil of Mars

Many people wonder what it would be like to step foot on Mars. Many people also wonder if the terrain of Mars could support life. With the help of recent discoveries by NASA’s Curiosity Rover, we are one step closer to finding out. Currently the Curiosity Rover is located in a region of Mars called “Rocknest.”

(Left) This image shows “Rocknest” as it would look on Mars.
 (Right) This image shows“Rocknest” under lighting conditions on Earth.

The rover took a sample of soil from this region. The sample was analyzed with its Chemistry and Mineralogy instrument, as known as CheMin for short. The CheMin uses an Alpha Particle X-Ray Spectrometer (APXS) in order to analyze samples. The CheMin shoots X-Rays at a sample of soil, and using a method called X-Ray defraction. They use X-Ray diffraction because each mineral has a distinct interaction with X-Rays. Using this method not only determines what minerals are in the soil, but also how abundant they are.

This image shows how X-Ray defraction works. Each ring represents a mineral and its abundance.

For a better understanding of how the CheMin works, check out this video:

This was the first sample the rover took. Part of the soil was determined to be basaltic and alkalic material. These materials are similarto the minerals found in Hawaii and other volcanic areas. This is expected because Mars is one of the most actively volcanic celestial bodies in our solar system. Some of the materials discovered include volcanic glass, silicon, aluminum, sodium, and potassium. Most of these materials are thought to have been formedthrough the breakdown of rocks by water, an essential part of determining if a planet can contain life. However, there are other processes that could break these rocks down, so scientists are not jumping to any conclusions.

Although all of this is preliminary, scientists are very optimistic about future tests.

The Ringed Planet

Astronomers have been looking up into the sky for ages. Ancients could see what appeared to be five distinct planets revolving around our very own Earth. One of the more recent astronomers, Galileo, had his curiosity spiked in a planet that had three celestial bodies connected together, the middle being the largest.  Could nature really allow such a monstrosity to take part in the great sky above? Even with telescopes, the planet seemed so small and very distant.

Years later, we know the planets revolve around the sun, and the three headed beast in the sky is really Saturn surrounded by its rings. And yet besides this, there is still so little we know about Saturn and its rings. Saturn's rings are actually made of a multitude of particles that range in size that revolve around Saturn due to its gravitational pull. However, these particles that make up the rings can stretch out up to hundreds and thousands of kilometers! What makes Saturn so interesting is that the rings are made out of ice and some types of rock. Since we know water is the beginning of life, it is no surprise that scientists are very intrigued about life on Saturn and its surrounding moons.

From the pictures you see of Saturn, you might think Saturn only has a couple of very large rings. Wrong! Saturn has thousands of tiny ringlets. Who would've known! But besides this, Saturn's rings have gaps in them. Some of Saturn's moons like Mimas have a large enough mass to affect some of the particles by its gravity. The gravity of the moons yank the particles out of the rings. And all of this is only the beginning of Saturn. The actual planet Saturn has many secrets that just need to be explored!