Sarah Cusson
The Red Planet: Why Scientists and Engineers are Captivated With Mars
Abstract: For years, scientists and engineers have been focusing all of their space exploration efforts on the planet Mars. What makes the red planet so much more special than any other planet in the universe? As it turns out, Mars’ atmosphere has that perfect mixture much like Earth's that makes life possible on its surface. In a quest to find out if there is life on Mars, scientists and engineers have discovered a flurry of information that could change the way they think about planet Earth. With that, and our insatiable quest to land man on another planet, Mars has that it factor when it comes to planets, making it desirable for machines and humans alike to explore.
Sarah Cusson is a senior studying Astronautical Engineering who spent a six-month internship designing the United States' next human rocket, SLS.
On September 12, 1962, President John F. Kennedy stood in front of the world and said that the United States would land a man on the moon by the end of the decade. In his speech, he said. "We choose to go to the moon in this decade and do the other things, not because they are easy, but because they are hard, because that goal will serve to organize and measure the best of our energies and skills..." [1]. While this goal seemed impossible at the time of the speech, just seven years later on July 20, 1969, Apollo 11 landed on the moon carrying three Americans. Today, the United States finds itself in a similar position as it was in 1962. It has always been our goal to further our knowledge on matters that are poorly understood, or to do the things that are hard. In 1962, that matter was landing a man on another planet besides Earth. Today, that matter is landing a man on Mars and returning him safely to Earth. However, there are plenty of planets in the solar system and universe, so why Mars? Why not Venus or Saturn or Jupiter? What makes Mars so special? Engineers and scientists have begun recently to answer this question and show just how close the United States is to getting a man to Mars.
Planets are Far Away and Hard to Get to
Planets are millions and millions of miles away from Earth. To put that into perspective, the distance between Boston and Los Angeles is about 3000 miles. Mars and Venus are the two closest planets to Earth. Due to not being on the same orbit, Venus and Earth are, at any one time, between 23.6 million miles and 162 million miles apart [2]. By contrast, Mars is anywhere between 33.9 million miles and 249 million miles away from Earth [3]. Say a car was traveling at highway speed of 65 miles per hour and did not stop on the way between Earth and Mars. At its closest point of 33.9 million miles away, it would still take 59.6 years to drive there. And, rockets need fuel just like cars. SpaceX's Falcon Heavy is by a ten-fold the cheapest "fuel source" to put any object into the orbit of Earth. For them, it costs about $2200 per kilogram to get something into lower earth orbit [4]. Lower earth orbit is the orbit at which most satellites orbit at as well as the International Space Station [5]. The orbit is around 200 kilometers above Earth's surface and is as close as an object can orbit around Earth without reentering the atmosphere and burning up. As is obvious here, it is incredibly expensive to get a small amount of mass just a little bit away from Earth. Therefore, it is most economical for the government and aerospace companies to explore planets that are closer as opposed to those that far away.
Venus is closer than Mars, Why Not There?
At the end of the day, aerospace engineers want to find a place where humans can survive and live. Aerospace engineers are engineers that research, design, test and build aircraft and spacecraft, both for commercial and military use. Part of this includes building spacecraft designed to explore the solar system. There are lots of signs that planets display that makes them a viable place for life, and thus interesting to aerospace engineers. One of them is being in the "habitable zone." Every planet in the universe orbits a star. Planets also absorb radiation from their star which heats the planet. In order for water to be found on a planet, it cannot be too far or too close to its star, or the water will not be in liquid form. The habitable zone is the zone around a star in which, if a planet is in this zone, there is the potential for life [6]. For the solar system, Venus, Earth, and Mars are in the habitable zone. Unfortunately, the atmosphere of Venus is made up almost entirely of carbon dioxide. In addition, the pressure on the surface of Venus is almost ninety times that of Earth [7]. This means that humans would immediately be crushed and killed if they landed on the surface of Venus. Therefore, Mars is closest planet on which a human could feasibly survive. This is of great interest to scientists and aerospace engineers as they are always trying to find a new planet for humans to explore.
Mars Used to Be Like Earth?!
Mars current atmosphere is about a hundredth as dense as Earth's current atmosphere. This means while Earth has an atmosphere full of the oxygen and nitrogen molecules that bodies need to survive on, Mars does not. The density of the atmosphere on the surface of Mars is the same density of atmosphere that Earth has at about 100,000 feet above its surface, which is about four times the height of Mount Everest. Mountaineers on Everest often have to bring supplemental oxygen canisters to survive at such a high altitude, entirely due to the density of air particles. When the density is lower, less particles of air enter the body with each breath, meaning the body is often starving for oxygen. Now, imagine trying to breathe at four times the summit height of Mt. Everest. It would be nearly impossible.
However, Mars' atmosphere wasn't always this thin. Billions of years ago, Mars had an atmosphere very similar to Earth's [8]. While the mixture of gases differed slightly, the density and quantity was similar. This was discovered when engineers sent a rover to Mars [9]. On board the rover was a machine that ingests Martian rock and determines the composition of the rock. The machine then told engineers and scientists that the composition of the rocks was different that those of Martian meteorites, leading to the conclusion that the atmosphere went through a change billions of years ago. This discovery is incredibly important to the future of Earth’s atmosphere. It is critical that geologists and aerospace engineers are able to figure out what caused this drastic change. If they are not able to figure out what happened, the same events could happen to Earth's atmosphere leaving humans with no air to breathe. Once a supported theory is established, the next big challenge will be for aerospace engineers to solve the puzzle of how to stop the same events from happening to Earth. A few theories have come to light since the beginning of the study. Currently, engineers believe that it is possible either an asteroid hit Mars and a portion of the atmosphere blew away in a violent upheaval or it was a result of millions of years of solar wind erosion [8]. Solar wind erosion is similar to the sand-blasting of a rock. By blasting the light particles (solar wind) at an object (Mars' atmosphere), it slowly eroded away. Regardless, engineers and scientists are constantly designing new rovers to send to Mars, test its atmosphere, and solve this mystery.
Life Outside of Earth
In addition to solving the mystery of Mars’ atmosphere, the rovers sent there have another critical mission. And that is, to answer the question that's never been answered before: Are humans alone in the universe? It is humans' nature to see if life exists beyond Earth. While no life has been found outside of Earth yet, Mars is a very good place to start looking. There are a few key components to indicate life existing on a planet. One of those is water. Another one is the existence of carbon. Carbon is the basis of all life and is necessary for organisms to exist somewhere.
In early 2009, NASA announced that through infrared scanning, they had found clouds or concentrations of methane on Mars [10]. Methane is a hydrocarbon which contains four hydrogen molecules and one carbon molecule. This discovery was a large indication that there was either life on Mars or there used to be life on Mars. It is also the first concrete evidence that exists showing the compounds for life exist in places other than Earth. Unfortunately, the Curiosity rover tested some air samples and did not detect methane or find signs of life [11]. This does not mean that methane does not exist on Mars. The rover simply has not found it yet, or the methane is not present in the atmosphere, but stored in the rocks below the surface. More testing needs to be done before any conclusions can be made.
Besides methane being a sign of life, it is also of high interest to propulsion engineers. The way a chemical rocket works is that when an oxidizer, a compound that causes the oxidation-reduction process to being, and a fuel are combined and ignited, the combustion process begins. The combustion process creates a large amount of heat in the resulting gases. Because the gases contain so much energy, when they are subsequently accelerated downward, the rocket goes up due to energy balance and thrust is therefore produced. However, in order to sustain this combustion and produce enough thrust to get to Mars, a large quantity of fuel and oxidizer is needed. With this comes extra weight to the vehicle, and, in the aerospace industry, weight equals cost. Methane is a cheap and common fuel used for rocket propulsion. It has been proposed by companies that they would travel to Mars with just enough fuel to get there. This decreased weight would save millions, maybe even billions of dollars over the course of the mission. Once at Mars, methane would be harvested from the planet. This harvested methane would thus be used as the fuel for the rocket to make the return trip to Earth. This innovative and cost-effective solution could help make a manned mission to Mars occur within the next fifteen years.
In addition to methane, the other key ingredient to life, water, has also been found on Mars. As recently as September 26, 2013, the Martian rover Curiosity found water in dirt samples it analyzed [13]. This discovery was actually a surprise for scientists, who were not actively testing for water. However, it is a huge step forward towards finding life on Mars. In addition, it helps validate a few theories. Gamma-ray evidence previously suggested that as much as one-third of the Martian surface was once covered in oceans [14]. Finding water helps validate this theory. In addition, it helps validate the theory that humans could thrive independent of Earth on Mars. One big concern with the prospect of humans on Mars is where the source of the water and food supply would come from. Previously, it was believed that there would need to be rockets sent every so often to resupply people with goods. However, with the discovery of water comes the new thinking that perhaps humans could survive without assistance from those on Earth.
So When Do Humans Make It?
While all these discoveries about Mars are important, they do not mean too much if aerospace engineers and companies cannot get a person to Mars. Currently, China, Russia, the United States, and Europe are working on vehicles that could make it to Mars. In addition, there are many commercial companies working on this cause. The most advanced of these companies is SpaceX, who is currently working on their capsule Red Dragon [15]. With the multitude of competitors and the large breadth of technology already in existence, it is very likely that humans will be landing on Mars by 2030. Who knows, a few short years later, you could be making a journey over to the red planet.
References
[1] J.F. Kennedy. (1962, September 12). Moon Speech - Rice Stadium. [Online]. Available: http://er.jsc.nasa.gov/seh/ricetalk.htm.
[2] J. Coffey. (2008, May 8). Venus Distance From Earth. [Online]. Available: http://www.universetoday.com/14152/.
[3] Staff. (2012, February 29). What is the Distance Between Earth and Mars? [Online]. Available: http://www.space.com/14729-spacekids-distance-earth-mars.html
[4] J. Strickland. (2011, September). The SpaceX Falcon Heave Booster: Why is it Important? [Online]. Available: http://www.space.com/14729-spacekids-distance-earth-mars.html
[5] Polaris. (2001). Types of Orbits. [Online]. Available: http://www.polaris.iastate.edu/EveningStar/Unit4/unit4_sub3.htm.
[6] The Habitable Zone. [Online]. Available: http://www.pbs.org/lifebeyondearth/alone/habitable.html.
[7] N. Redd. (2012, November 16). Venus' Atmosphere: Composition, Climate and Weather. [Online]. Available: http://www.space.com/18527-venus-atmosphere.html.
[8] T. Phillips. "Solar Wind Rips Up Martian Atmosphere," in 2008 Huntsville Plasma Workshop, Huntsville, AL, 2008.
[9] J. Tuff et al. "Volcanism on Mars Controlled by Early Oxidation of the Upper Mantle," Nature, vol 498, pp 342-345, June 2013.
[10] B. Stiegerwald. (2009, January 15). "Martian Methane Reveals the Red Planet is not a Dead Planet." [Online]. Available: http://www.nasa.gov/mission_pages/mars/news/marsmethane.html.
[11] A. Chang. (2013, September 20). "NASA Rover Finds No Hint of Methane in Mars Air." [Online]. Available: http://www.sci-tech-today.com/story.xhtml?story_id=030000NUXUTU.
[12] Glenn Research Center. "Combustion." [Online]. Available: http://www.grc.nasa.gov/WWW/K-12/airplane/combst1.html
[13] M. Wall. (2013, September 26). "Curiosity Rover Makes Big Water Discovery in Mars Dirt, a 'Wow Moment.'" [Online]. Available: http://www.space.com/22949-mars-water-discovery-curiosity-rover.html
[14] U. of Arizona. (2008, November 18). "Gamma-Ray Evidence Suggests Ancient Mars had Massive Oceans." [Online]. Available: http://www.sciencedaily.com/releases/2008/11/081117212321.htm
[15] Karcz et al. "Red Dragon," October 2011. Unpublished. Avaiable: http://digitalvideo.8m.net/SpaceX/RedDragon/karcz-red_dragon-nac-2011-10-29-1.pdf.