Mars Missions

Mars has attracted human interest throughout history. The War of the Worlds (1898) by H. G. Wells, about an advanced Martian civilization that came to attack Earth, was inspired by the work of the Italian astronomer Giovanni Schiaparelli, who observed canali (channels) on Mars. (The Italian word canali was mistranslated as "canals.") This led to interest in the possibility of intelligent life on Mars.

Although it is now known that there is no intelligent life on Mars, planning for exploration of the Red Planet is at an all-time high. The question of whether simple life ever arose on Mars is a strong motivation for exploration. Other questions include how the Martian climate evolved and how it differs from that on Earth and how the surface and interior of Mars evolved.

Proposed Missions

With the long-term goal of human exploration, many preliminary missions are needed to address these questions and engineering issues. Water is the link between these goals, and the plan of the National Aeronautics and Space Administration (NASA) is to "follow the water." The strategy will be to sample the Martian environment through in situ experiments and by bringing pieces of the planet back to Earth.

The proposed mission plans for the next decade include one or more spacecraft launches every two years. These spacecraft will be designed to address the primary scientific questions and conduct the experiments necessary to prepare for the launching of astronauts to Mars. The vehicles will probably alternate between orbiter and lander spacecraft. Beginning in 2007, there will be less expensive spacecraft, termed "scouts," which will supplement the program by addressing objectives not targeted by the other missions.

Life and Water on Mars

Life on Earth contains organic carbon and needs water and energy to exist. Searching for carbon in the soil and ice on Mars and understanding how the amount of carbon has changed during that planet's history are primary goals of future Mars missions. It is important to understand where water (ice, liquid, and vapor) exists on Mars today, how much there is, and how it is transported around the planet. There may have been much more liquid water on Mars in the distant past. Flowing water may have deposited sand and silt in the bottoms of lakebeds or oceans. If standing water once existed, these areas will be a primary place to search for fossilized life.

The Mars Odyssey orbiter spacecraft, launched in April 2001, is designed to detect evidence of ancient water on Mars and possible locations of current water in the subsurface. The two rovers that will be sent to land on Mars in 2003 will study rocks and soils to determine whether water was ever present at those sites.

The Mars Reconnaissance Orbiter, planned to be launched in 2005, will have cameras that can see beachball-size rocks on the surface. This will allow scientists to compare surface to orbiter observations and may indicate which parts of the surface were created by volcanic flows and which were created by sand and silt deposited in water.

Scientists would also like to know how the Martian climate has changed since the ancient past. The atmosphere of Mars contains mostly carbon dioxide, with very little water. This means that there are only very thin clouds that occur rarely. Because it is very cold on Mars and the atmosphere is thin, there is no rain. Mars also has severe dust storms during the southern hemisphere summer.

However, if liquid water flowed on Mars in the distant past, the climate might have been very different from what it is today. To understand those changes, it is necessary to understand the present-day climate. The Mars Odyssey spacecraft will gain insight into the climate, but the Mars Reconnaissance orbiter will contain instruments specifically designed to address these issues.

Astronauts on Mars

Landing astronauts on Mars will not be easy. A spacecraft with humans on-board will be much heavier than any previous spacecraft and thus will enter the Martian atmosphere at a very high speed. It therefore will need a new type of aeroshell and a strong parachute to slow it down.

With humans onboard, a safe landing becomes more critical—for instance, it will be important to avoid large rocks or cliff walls. To do that, instruments and software are being developed to view the ground below the spacecraft just before landing and automatically select the safest touchdown spot. The plan is to have the Mars 2007 spacecraft demonstrate these capabilities.

While on the surface, the astronauts will need to have continuous communication with Earth. This will require a network of communication satellites around Mars to provide the connection at all times of the Martian day and night. Most future science orbiters will be designed to continue in use as communications satellites. There is also a plan to have an Italian Space Agency communications satellite at Mars in 2007. Since it is difficult to bring much to Mars, rocket fuel to return to Earth probably will have to be made on the surface.

It will be very difficult for humans to survive on Mars. One of the main concerns is the radiation level on the surface of the planet. The Mars radiation environment experiment, named MARIE, is flying on the Mars Odyssey spacecraft and will help investigate the level of radiation above the atmosphere.

Understanding how much water is present and where it is located will be crucial for human survival. If water is found in deep reservoirs, instruments such as drills will be designed and tested to bring it to the surface. There also may be very small amounts of water in the soil that instruments can separate out.

If enough water and oxygen are not brought to Mars, instruments will be needed to create them on the surface. Bringing enough food will also pose a challenge. It is vital to learn enough about the soil on Mars to determine whether it is safe and can be used for growing plants for food. In addition, the soil may corrode the spacecraft or the space suits. The survival of the astronauts also will depend on having enough power to operate all the necessary machinery.

With more sophisticated instruments on Earth, scientists are certain to learn a great deal from returned Martian rock and soil samples. In the second decade of the proposed Mars plan, NASA intends to return the first sample in 2014 and the second in 2016.

see also Astrobiology (volume 4); Human Missions to Mars (volume 3); Living on Other Worlds (volume 4); Mars (volume 2); Mars Bases (volume 4); Mars Direct (volume 4); Natural Resources (volume 4); Planetary Protection (volume 4); Power, Methods of Generating (volume 4); Resource Utilization (volume 4); Scientific Research (volume 4); Telepresence (volume 4); Terraforming (volume 4).

Leslie K. Tamppari

Internet Resources

Brians, Paul. "Study Guide for H. G. Wells: The War of the Worlds (1898)." Washington State University. <http://www.wsu.edu:8080/~brians/science_fiction/warofworlds.html>.

"Marie Instrument."2001 Mars Odyssey. Jet Propulsion Laboratory. <http://mars.jpl.nasa.gov/2001/instruments/lander_marie_text.html>.

Mars Odyssey. Jet Propulsion Laboratory, 2001.<http://mars.jpl.nasa.gov/2001/>.

Migration See Living on Other Worlds (Volume 4).