Blue on the Big Red-A History of Water and Life on Mars

Tej Mehta

Originally published November 26, 2015

Image of Mars as taken by the Hubble Space Telescope

Are we alone in the universe? Humanity has been searching for evidence of life elsewhere in the cosmos for hundreds of years, and recently, the key to life on Earth, liquid water, was found on our neighboring planet Mars. In September of 2015, the National Aeronautics and Space Administration (NASA) confirmed evidence of liquid, flowing water on the planet Mars. The lead author of the new report, Lujendra Ojha, noted the presence of hydrated minerals on some of the hills of Mars, which appear to flow and change direction over time. Given the growing public interest in the Red Planet, in part evidenced by the success of modern space dramas like The Martian, we wanted to highlight the importance of NASA’s new discovery in the context of previous water-related discoveries on Mars. While few people expect to find little green men, the discovery of even single-celled organisms on the Red Planet would finally answer one of humanity’s greatest questions.

Scientists have speculated about the possibility of water on Mars since the early days of telescopic observation, when William Herschel, the famous German astronomer, recorded his observations of the Red Planet in the 1780s, noting striking similarities between Mars and Earth. Like other scientists at the time, Herschel believed that Mars’s polar ice caps were evidence of water, but he also believed that large, dark spots on Mars’s surface were oceans and clouds. Herschel went so far as to postulate that the differences in surface topography in relation to seasonality were caused by inhabitants on Mars who were growing vegetation.

Herschel’s popularization of the theory of Martian residents likely influenced one of the greatest Mars sensationalists, Percival Lowell. Taken in by a popular scientific idea of the 1890s, Lowell constructed the Lowell Observatory in Flagstaff, Arizona to help observe and make detailed drawings of the planet’s surface, believing that the “inhabitants” of Mars were building visible canals on the Martian surface to direct water flow. His ideas were rejected by later astronomers, though the Lowell Observatory was ultimately used by Clyde Tombaugh to discover the dwarf-planet Pluto and Lowell himself was able to generate tremendous public enthusiasm to hunt for life on the Red Planet.

Despite ongoing public and scientific interest, water-related discoveries on Mars did not truly surmount until modern analytical techniques for astronomical observation were developed. In the 1930s, astronomers began to observe Mars using the techniques of spectroscopy, which works by splitting light into different wavelengths and analyzing those wavelengths separately. Early experiments by Walter Adams and Theodore Dunham showed effectively no water vapor or oxygen in the Martian atmosphere; later, more refined experiments determined the amount of oxygen to be around one percent that of Earth and even water vapor was detected in small quantities, though not until 1963. Eventually, and after years of contention, a number of observations determined that Mars has two polar water-ice caps –  one that has a perennial dry-ice coating and one that acquires a dry-ice coating during the Martian winter.

Modern spacecraft-based Mars exploration began with the Mariner 4 flyby in 1965. The spacecraft’s images and measurements showed a very thin Martian atmosphere and a pox-marked surface, indicative of many asteroid collisions and little to no geologic activity. Such a lack of geologic activity suggested a lack of flowing water on the Martian surface and a thin atmosphere implied that any liquid water on the surface would either quickly boil or freeze. These observations led many to question the possibility of any significant water on the surface, and the chance of finding life on Mars seemed unlikely to much of the scientific community.

The view of Mars as a “dead” planet hampered future exploration; however, nearly a decade after the Mariner 4 mission, Mariner 9 was the next probe to reveal significant information of past water on Mars in 1971. This discovery rekindled scientists’ hope to find water and life on Mars. While previous spacecraft had only conducted flybys, Mariner 9 was the first to enter the orbit of another planet and remain there for its entire mission, which proved to be a much more desirable method of planetary observation. Mariner 9 was able to reveal not only the presence of riverbeds and canyons, but also weather fronts, fog, and other past and present indicators of liquid water on Mars.

The success of the Mariner program, and Mariner 9 specifically, influenced the design of the following Viking missions to Mars. Between 1976 and 1982, the probes Viking 1 and Viking 2 provided a wealth of information about Mars and were the first successful rovers to land on the Martian surface. Chemical analysis of the soil by the rovers indicated the possible presence of organic materials and water in the surface, though it was noted that the presence of strong UV light and perchlorate in the soil would make it extremely difficult for life to exist in the Martian top-soil. Combined data from the Viking orbiters and rovers showed a wealth of information for water-based erosion on the Martian surface. Strong evidence was found for past river valleys, natural dams, streams, rainfall, and even mud caused by heating of select locations by meteor strikes or volcanism.

The Viking program was retired on November 13, 1982, and the information garnered by it has been in use to this day. Since then, a variety of data about water on Mars have been collected by multiple probes and rovers. In the late 90s, the Mars Global Surveyor discovered evidence of past lava flows, implying geologic activity and warming. In 1997, Pathfinder found evidence of wet soil. Between 2002 and 2008, Mars Odyssey, Phoenix, and Mars Express each found evidence of past water distribution, while in 2004, Opportunity found evidence of past oceans and coastlines. Some of the latest, most influential evidence for water on Mars comes from the Mars Reconnaissance Orbiter (MRO). The September 2015 announcement by NASA came in light of flowing, hydrated minerals detected by MRO.

Warm seasonal flows in Newton Crater on Mars as captured by Mars Reconnaissance Orbiter

Using similar spectroscopic techniques as Walter Adams and Theodore Dunham had nearly 80 years prior, MRO was able to detect these hydrated minerals on “recurring slope lineae” when local temperatures were above -10 degrees Celsius. While flowing water was previously thought to be impossible given current conditions on the Martian surface, the extreme saltiness of these hydrated minerals could allow for liquid water to exist, much like how salt spread on roads can help keep water liquid below 0 degrees Celsius. Of course, the big question on everyone’s minds is now “Can we find evidence of life on these slopes?” to which the answer is “Maybe”. The hydrated minerals are not present on the surface year round, and evidence for ground water beneath the slopes is still unclear. Additionally, the extreme saltiness of these minerals and the possible water around them is toxic to all but the most resistant forms of known life. Future expeditions will attempt to characterize more recurring slope lineae as well as other potential sources of current water on Mars, and the Curiosity rover is currently searching for fossilized bacteria on the Martian surface when it’s not too busy taking selfies.                 

                 Self-portrait of Curiosity rover taken on November 1, 2012

Faced with the current worldwide situation of economic instability and crisis, the value of Mars-research and space exploration in general are often undercut, such as with the Obama administration’s 20% budget reduction of NASA’s planetary-sciences division – but the importance of Mars-research and space exploration cannot be overstated. From an economic standpoint, the discovery of water on Mars would make colonization and resource-extraction efforts profoundly more plausible and could be a long-term solution to humanity’s population explosion and resource-mismanagement. Not only is Mars-exploration economically enticing, but humanity has been fascinated by the Red Planet since ancient times, and the prospect of life on Mars feeds our curiosity about the universe and could help tell us whether or not Earth is the only planet capable of harboring life. From William Herschel with his telescope, to NASA’s Jet Propulsion Lab, we have spent hundreds of years studying Mars and launched over 50 missions to investigate the planet. The discovery of water on Mars is not simply bringing closure to decades of past speculation, but is the beginning of new possibilities and a chance to challenge our current solitude in the universe.

Edited by: Marika Wieliczko

Tej Mehta is a graduate student in the Rollins School of Public Health and can be contacted at tej.ishaan.mehta@emory.edu.

Protons for Patients at Emory - Cancer Treatment with a Big Cost?

Tej Mehta

Originally published October 14, 2015

photo by: paula tyler

In May of 2013, Emory Healthcare and the Winship Cancer Institute (in partnership with a private funding entity) began construction of the Emory Proton Therapy Center. The $200+ million, 107,000 square-foot facility, which is slated to open in January 2017, will be the first of its kind in Georgia. Based on current construction estimates, the Emory facility will be the 17th operating center nationwide, and will prominently feature new “pencil beam scanning” technology, a major development in the field of proton therapy. The technique itself holds significant promise for many patients in the Emory Healthcare system, but is the potential benefit of proton therapy worth its additional price? The Emory facility has partnered with Advanced Particle Therapy LLC, a proton therapy developer, to help fund the construction and operational expenses.

In 1946, Robert R. Wilson at the Harvard Cyclotron Laboratory, first proposed protons as a therapeutic tool, and the first treatment in the United States occurred in 1954 at the Berkeley Radiation Laboratory. Due to major engineering limitations, proton therapy continued to be used sparingly for many years, predominately for research purposes. In 1989, the first hospital-based center was developed at the Clatterbridge Center for Oncology in the UK, followed by the first US hospital-based center in 1990 at Loma Linda University Medical Center. Since that time, proton therapy centers have been developed at a slow but steady pace, currently numbering 15 operating facilities and an additional 20+ centers under construction. This implies a current access rate of 1 facility for approximately every 20 million US citizens. Globally, there is a dramatic upsurge of interest in proton therapy, with nations like Norway developing widespread access by commencing construction on approximately 1 facility for every 1 million inhabitants.

Like other forms of radiotherapy, proton therapy kills cancer cells by causing direct or indirect DNA strand breaks. In modern external beam radiotherapy, tumor-specificity is achieved by physically shaping the beam to minimize exposure of normal tissue to unnecessary radiation; however, because high energy X-rays continue to travel through tissue, some radiation is always deposited in normal tissues in the exit path of these beams. Protons, like high energy X-rays, can also be shaped to match the shape of the tumor,  but because of their unique physical property of losing energy while traversing tissue and then depositing all of their energy at a pre-defined depth (based on the initial energy of the beam), there is close to zero exit dose. The result is that while other forms of radiation therapy will deliver radiation to healthy tissue beyond the tumor, proton therapy delivers little to no excess radiation to healthy tissue posterior to the entry beam. This special ability of protons is due to a phenomenon called the “Bragg Peak,” which represents the precipitous and sudden loss in energy that stops protons. Modern proton therapy clinics, such as the Emory facility, also use the previously ​​mentioned technique - pencil-beam scanning - which is analogous to 3-D printing. Like 3-D printing, where thin layers of material are repeatedly applied to make a larger 3-D shape, pencil-beam scanning continuously applies thin layers of protons to a tumor until the entire tumor is treated with radiation. This unique capacity not only eliminates radiation damage past the stopping point of the beam, but also reduces radiation damage to normal tissues all around the tumor. These advantages of proton therap​y have been lauded by clinicians and the therapy is generally recognized as particularly useful in patients with a likelihood of long-term survivorship, such as children and young adults. These individuals are typically at greater risk of developing organ dysfunction and secondary cancers as a result of radiation to their normal tissues. Additionally, in situations where an adequate dose to control the tumor simply cannot be safely deposited with conventional modalities, proton therapy is often the best recourse.

Despite these apparent advantages, proton therapy has received significant criticism, both with regards to cost and the level of evidence documenting its true effectiveness. Currently, the primary concern about proton therapy is whether the obvious dosimetric advantages result in “cost-effective” clinical advantages. The upfront construction cost of a multi-room proton therapy facility is well over $100 million, and various analyses have projected that treatment with protons is twice as expensive as X-ray radiotherapy. However, other studies have determined proton therapy to be reasonably priced for most cases, particularly given the potential costs of treating adverse effects caused by standard radiotherapy. For example, one study published in the journal Cancer in 2005 found the average cost of treatment for conventional radiation therapy and proton therapy to be $5,622 and $13,552 respectively. However, the same study found the cost of treating adverse events from conventional radiotherapy and proton therapy to be $44,905 and $5,613 respectively, demonstrating that while the upfront cost of proton therapy may be high, the total costs are significantly reduced.

The other primary criticism against proton therapy is whether or not it is truly as effective as its proponents claim it to be. Thus far, there have been few controlled, randomized clinical trials to demonstrate improved survival or quality of life with proton therapy over other forms of external beam radiotherapy. One such trial randomized patients with ocular melanoma to particle therapy with Helium (similar to proton therapy) against a localized form of radiation known as plaque brachytherapy, and reported superior clinical results for patients on the Helium therapy arm. Several non-randomized trials have supported the clinical benefits of proton therapy. Conversely, detractors of proton therapy point to the lack of randomized clinical trial data as cause for concern with proton therapy, while proponents argue that no clinician has true equipoise to conduct such a randomized trial, stating that to knowingly withhold proton therapy from patients who could benefit from the treatment is unethical. Other critics of proton therapy raise concern over the potential inaccuracy of the exact placement of the Bragg Peak within the tumor. Because of the sudden deposition of energy caused by the Bragg Peak, small errors in measurement or slight movements of the patient could cause a dose-shift. Most modern proton systems deal with this by reducing error through a series of technical refinements, and by performing what is known as “robustness evaluation,” as well as accounting for this uncertainty through a process known as “robustness optimization”. ​

Emory Healthcare and its affiliates have weighed the costs and benefits of proton therapy and elected to build the facility. The construction of a proton therapy center in Atlanta by Emory Healthcare demonstrates Emory’s conviction to patient care and treatment options and aims to improve the survival and quality of life outcomes of many patients. As the first proton therapy center in Georgia and one of only a handful of treatment centers in the country, Emory has again distinguished itself as a nationwide leader in healthcare.

Edited by: Carson Powers

Tej Mehta is a student in the Rollins School of Public Health and can be contacted at tej.ishaan.mehta@emory.edu.

Explained At Last: Why Alkali Metals Explode in Water

Benjamin Yin

Originally published April 14, 2015

Photo by: Kristen thomas and Jadiel wasson

In the pilot episode of the iconic 80s TV show, MacGyver, the titular character made his debut as a resourceful secret agent by making a sodium bomb to take down a wall, rescuing a couple of scientists. For MacGyver, with his extensive knowledge of the physical sciences, the process was simple: he immerses pure sodium metal inside a bottle of water and the explosive reaction between sodium and water is great entertainment for viewers of all ages.

Today, this little display of pyrotechnic shenanigans is often seen in high school chemistry demos. Alternatively, one can find many dozens of internet videos documenting this violent reaction between alkali metals like sodium or potassium and water, often accompanied by exclamations and whistles of joy. It’s no surprise that some of these videos have also gone viral. This amusing diversion of chucking alkali metals into water to watch it explode has been around since the 19th century and scientists have had a solid description of the nature of this reaction for about as long. Or so we thought.

The classic explanation of elemental sodium’s volatile reaction with water involves the simple reduction-oxidation chemistry of sodium and water: electrons flow from sodium metal into the surrounding water, forming sodium hydroxide and hydrogen gas. This is a very fast reaction that produces a lot of heat. Hydrogen gas is extremely flammable in air, and in the presence of a heat source, this mixture can lead to a hydrogen explosion, not unlike the infamous incident that allegedly set the Hindenburg zeppelin aflame. The release of the large amount of energy in these reactions results in rapid expansion of the surrounding gas, which is what causes chemical explosions.

Generations of chemists have accepted this seemingly obvious explanation without much deliberation. It is perhaps surprising then, that one curious soul decided to look at this century-old reaction more in-depth.

Philip Mason earned his PhD in chemistry and has co-authored more than 30 scientific papers, but is probably better known for his YouTube channel, where he regularly posts videos, often in vlog format, under the pseudonym “Thunderf00t” (yes, that’s two zeros substituting for the letters “O”). His favorite post topics are often pieces of popular science he encounters, and Mason has earned the support of a huge public following with his YouTube channel. In 2011, using donations from some of his more than 300,000 YouTube subscribers, Mason purchased the materials and consumer grade high-speed cameras necessary to look at what he thought would be “home chemistry.”

The YouTube project, it turns out, raised many questions, for which Mason found traditional answers unsatisfactory, namely the explosive nature of alkali metals in water. Compelling footage also showed a secondary gas explosion above the water surface that resembles a hydrogen explosion, demonstrating that the initial stronger and faster explosion can’t be explained with our traditional understandings of this reaction. Some scientists have suggested, instead, that the explosion is caused by the sheer amount of heat released during the reaction. If this were the case, the heat would boil the water and a rapid generation of steam leads to explosion. Mason remained unconvinced. A key insight by Mason and his colleagues was that as hydrogen and steam are generated when the alkali metal comes into contact with water, the interface between the metal and water should be blocked off by the products and therefore inhibit further reaction. This would result in the exact opposite of the explosive reactions being observed. Crucially, immersing solid chunks of sodium and potassium under water still results in rapid explosions, so this too could not be the explanation for the initiation of the explosion. These enigmas led Mason to bring his YouTube project into the lab.

To get a better look at the reaction, Mason and his colleagues turns to research grade high-speed cameras. Filming at around 10,000 frames per second, they were able to capture the beginning of the reaction between alkali metals and water in astounding detail. What they captured is striking: the reaction is immediate, and the metal shatters on contact with the water surface. Within two-ten thousandths of a second, spikes of metal are flying apart from anywhere the surface touches water. As the sheer force of the rupturing metal bursts forth, a brilliant blue wash appears to stain the blast of water in the very next frame. This stunning blue color is due to solvated electrons in water, which is usually far too short-lived for people to see.

What isn’t so easy to interpret are the metal spikes flying apart, piercing the water in the process. However, with some chemical intuition and computing time on supercomputers, Mason and his colleagues came up with an explanation for this observation that ultimately describes the explosive nature of alkali metals in water.

When large numbers of electrons escape from the alkali metals into the surrounding water, the metal itself becomes extremely positively charged. Like the static charges that can make our hair spike up for that mad scientist look, the positive metal atoms now repel each other, except with much more violent force. Atoms that were previously bonded together as a solid now suddenly fly apart at extraordinary speed. This, in turn, exposes fresh metallic surfaces to water for the explosive reaction to take place. This little-known phenomenon is called Coulomb explosion.

The immediate application of this knowledge for preventing explosions in industrial use of alkali metals will be useful. Just as important, the discovery of this mechanism of explosion in a chemical reaction over a century old reminds us not only of how little we know, but also how much we simply fail to even consider. In the face of public apathy for science, it is encouraging that such a significant scientific discovery should come from a YouTuber, funded partially by the YouTube community, and documented in vlog format throughout the research process. It leaves us wondering what other remarkable discoveries such public engagement could lead to.

Mason and his colleagues published their research in the February issue of Nature Chemistry, they acknowledged the support of his YouTube followers.

Here's the video:

Link for article: 

http://www.nature.com/nchem/journal/v7/n3/full/nchem.2161.html

Edited by: Marika Wieliczko

Solar Water Splitting: Future Paths to Clean Unlimited Energy

Marika Wieliczko

Originally published April 8, 2015

photo by: kristen thomas

With recent advances in science, the ability to artificially split water – much like what plants do all the time – might be humanity’s way of finally having access to unlimited clean energy.

Looking back, one of the most important scientific developments of the 20th century was the industrial synthesis of the compound ammonia from nitrogen and hydrogen. Analogous to the oxygen atom in water, H2O, ammonia, or NH3 is the most basic combination of nitrogen with the simplest element, hydrogen. Developed initially for military applications, the revolutionary Haber-Bosch process, compresses nitrogen gas and hydrogen gas under extreme conditions to yield ammonia.

The ability to produce ammonia from its elements facilitated an unprecedented boom in human population. Living things require useable forms of nitrogen for making proteins and DNA, but most of the nitrogen on the planet is in the form of unreactive nitrogen gas, which is the bulk of the air we breathe. Unlike the oxygen, which most organisms use for metabolism, nitrogen gas is almost completely unreactive. Only a handful of microorganisms are capable of “fixing” the N2, by breaking its very strong nitrogen-nitrogen bond so that the individual nitrogen atoms can be used in more complex molecules required by the organism. Before the Haber-Bosch process was developed, the amount of usable nitrogen on the planet was limited by the rate at which these microorganisms could enrich the soil with usable nitrogen to incorporate into the food chain, which by then had essentially plateaued. Once human beings mastered the ability to fix nitrogen on their own, the bottleneck that had been keeping population growth in check was gone, and in only one hundred years, 1.6 billion people grew to over 6 billion.

Such a dramatic and sudden increase in the population has led to fears of overpopulation, and the consequences for the environment of the additional demand for resources and surplus waste. Scientists have long recognized the need for sustainable energy; most current sources, such as burning fossil fuels, are not renewable and release excess waste that is unlikely to be inconsequential on this massive global scale. One of the most promising sources of sustainable energy is sunlight, and provided we can find ways to convert that light energy into solar power we can use efficiently, could sustain all of the planet’s energy needs for generations to come.

Plants, and a handful of microorganisms have been capturing and harvesting solar energy for millions of years through photosynthesis. In this process, energy from sunlight is used to convert carbon dioxide and water into carbohydrates, or sugars. The waste product is molecular oxygen, the essential component of the air we breathe. The energy is stored in the chemical bonds until they are broken during metabolism. In effect, all of the oxygen on Earth originated through this process, and allowed for the evolution of complex life.

photo by: kristen thomas

Whether it occurs in plants or bacteria, photosynthesis begins with the absorption of light. The light energy is transferred to an electron in the light-absorbing molecule. In this energetically excited state, the electron can be captured by a neighboring acceptor molecule, leaving a positive “hole” behind. The electrons to neutralize these positive holes are harvested from water by the oxygen-evolving complex, or OEC. The OEC contains four manganese ions and one calcium, arranged in a cube-like shape, along with several oxygen atoms and water molecules. The cluster takes two water molecules and combines them into molecular oxygen, O2. The process has been studied thoroughly, but many of the details are not completely understood. We do know that the process occurs in steps, and the positively charged hydrogen ions, H+, are released in sequence, and kept separated from the negatively charged electrons in order to generate a potential across the cell, that it can use for energy.

Both metabolism and combustion of fossil fuels are effectively the reverse of photosynthesis. In the presence of oxygen, molecules that contain carbon and hydrogen are converted into carbon dioxide and water. Despite debates over the existence or causes of climate change, scientists have long anticipated the need for sustainable sources of renewable energy, and have recognized that one of the most promising paths is to learn from nature and develop technology for artificial water splitting and solar energy capture.

Significant progress has been made in recent years, with, for instance, the appearance of so-called “artificial leaves”. Usually, in artificial systems and plants alike, each of the overall reaction steps is accomplished by separate components. One component absorbs light, another generates oxygen and still another for managing protons or hydrogen production, in addition to other components that may be needed to keep the oxygen and hydrogen reactions separated, as both do not usually occur under the same conditions.

photo by: kristen thomas

​​One particularly exciting system was recently reported by researchers in China and Israel. These scientists, led by Zhenhui Kang, have discovered that by combining two materials, carbon nitride and carbon nanodots, an indirect route involving hydrogen peroxide allows for a synergistic effect. While each component alone is a capable catalyst, carbon nitride is quickly deactivated by the products it generates. When combined however, each component alleviates shortcomings of the other. This solid material, when placed in water and irradiated with light, generates a 2:1 ratio mixture of H2 and O2 gas. This particular system is difficult to understand, and almost seems too good to be true.

The major drawback is that this mixture of gases is explosive, ideally they would be generated in separate, isolated components. Another weak point is the overall efficiency, when comparing the energy stored in the chemical bonds of O2 and H2 that are formed to the energy in the light needed to drive the process. While the efficiency is far from optimal, the material is made of abundant elements and is extremely stable, and after 200+ days of continuous use, the material continues to steadily split water using sunlight.

Nature often serves as a source of inspiration or guidance, but artificial systems address different needs. While it is amusing to imagine putting water into the gas tank of a solar-powered car, with only water vapor on the tailpipe end, the need for technology for splitting water into O2 and H2 is more extensive than that. The Haber-Bosch process, after all, relies on the reaction of N2 and H2, and the ultimate sources of H2 are typically fossil fuels. Water splitting technology, especially if powered by sunlight, holds enormous promise for changing the way we use resources by closing loops in inefficiency and reducing or even eliminating unnecessary waste. Solar water splitting continues to be an active and exciting field of research, and in the face of impending urgency for green technology, may one day be called the most important scientific development of this century.

Edited by: Anzar Abbas