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About this Article
Written by: Denise Nemenz
Written on: May 1st, 2005
Tags: space, aerospace engineering
Thumbnail by: NASA/JPL/Cornell
About the Author
Ms. Nemenz was a junior in the College of Letters, Arts and Sciences at the University of Southern California in the fall of 2005. She was majoring in Physics and Computer Science.
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Volume VII Issue I > Terraforming Mars
Mars, a planet once warm enough to support water, is now a cold and dry wasteland unable to sustain human life. Many scientists believe that through the introduction of carbon dioxide to the atmosphere, the Martian environment can be terraformed into a planet like Earth. Possible methods for introducing carbon dioxide include the spread of green plants and the construction of CFC factories. A lingering question, however, is whether it is ethical to reform an entire ecosystem.
Imagine walking outside your home on a warm summer's night and feeling a cool breeze hit your face. You walk across your lawn and feel the soft grass bend beneath your feet. Then, you look up at the beautiful full moons?

Introduction

NASA Mars Exploration Program
Figure 1: Erosion on Mars
Someday this fantasy could be reality, as it may be possible for humans to inhabit the planet Mars. But, for now, the surface of Mars is a frozen wasteland void of liquid water, a necessary condition for life. Many scientists, however, believe that this has not always been the case. Eroded canals and networks of valleys indicate that Mars' surface was once warm enough to support running water [1] (see Fig. 1). For unknown reasons, the planet cooled down rapidly, freezing the majority of the water into the ground [2]. Because the surface of Mars did not contain enough of the minerals that cause volcanic activity, the water was unable to be recycled into the atmosphere. Over the years, however, bursts of heat have allowed some water to escape into the atmosphere in the form of clouds and fog [2]. This has led to the Mars of today—a lifeless planet with no accessible water.
But because Mars once had a warm environment suitable for life, some scientists believe that such an environment can be recreated. Most specialists believe that it is possible, but not without much effort. Researchers such as planetary scientist Chris McKay have been developing ideas to terraform Mars; that is, modify the conditions of Mars so that it becomes more like Earth [1]. In order to understand how this might be possible, it is important to first look at what key conditions make Mars uninhabitable in the first place.

What needs to be changed?

Mars is the most suitable planet in our solar system for human habitation because it bears some semblance to Earth -- a similar rotation rate and adequate surface gravity -- that will make it easier for humans to adjust. A similar rate of rotation will make the days feel about the same length as Earth days, and adequate surface gravity will allow our muscles to function properly [3]. That being said, Mars possesses many physical characteristics that are not conducive to human life. Although an incredible number of nuanced changes would have to be made to make Mars inhabitable, the following will describe the two main areas that would need to be changed: atmosphere and surface temperature.

Atmosphere

The current Martian atmosphere is far too hostile to support the human body. One problem is that the atmospheric pressure on Mars ranges from six to ten millibar, which is less than one percent of Earth's atmospheric pressure at sea level: 1000 millibar [4]. The importance of pressure stems from the scientific certainty that higher pressure states will move into lower pressure states. If the atmospheric pressure is lower than a human's lung pressure, then that person's lungs will burst. The average human lung pressure is around 250 millibar; Mars' atmospheric pressure will need to be raised at least to an equivalent amount [3].
A second problem is that the elemental composition of the Martian atmosphere little resembles that of Earth. The majority (95.32%) of the Martian atmosphere is carbon dioxide, and oxygen only constitutes a mere 0.13% [5]. On Earth, the two main elements are nitrogen (75%) and oxygen (23%). Carbon dioxide makes up only .05% of the Earth's atmosphere ("Earth"). Humans respiratory functions require that oxygen make up at least 13% of the atmosphere, and that no more than 10% of the atmosphere be carbon dioxide [3]. The abundance of carbon dioxide found on Mars is not necessarily an obstacle, however. Although carbon dioxide is not healthy for the human respiratory system, plants and other photosynthetic organisms readily utilize it. Therefore, the large amount of carbon dioxide could be used by those plants during photosynthesis to convert the atmosphere into the more valuable element, oxygen. This concept of using plants to change the atmospheric composition is one of the cornerstones of current theories for terraforming Mars.