Why Go to Mars?

On the occasion of the millennium, the President and the First Lady have called upon citizens to "honor the past" and "imagine the future." In this spirit, the White House Millennium Council, along with the U.S. Department of Education, the National Aeronautics and Space Administration and its Jet Propulsion Laboratory, the National Endowment for the Arts, and the J. Paul Getty Trust, has launched a national arts, sciences, technology, and education initiative entitled The Mars Millennium Project. At the heart of this project is heightened interest about Mars.

People have been interested in the planet Mars for thousands of years. The ancient Egyptians and Babylonians gave names like "The Red One" and "The Star of Death" to the reddish star that wandered through the night sky. The Greeks and Romans also thought it looked threatening and warlike so they named it for their war gods, Ares and Mars.

Many people used to believe that Mars must be inhabited. So until 1965, science fiction entertained people with stories of swashbuckling adventures with the natives on Mars or frightened people with tales of Martians invading Earth. But in 1965, a little spacecraft called Mariner 4 flew by Mars and took a few pictures of the southern hemisphere. Everyone was disappointed to find out that there were no Martians –– Mars was a cold, dry desert. In fact, until 1971, people thought Mars was like the Moon –– covered with nothing but meteor craters.

Then the first Mars orbiter took pictures that showed huge volcanoes and giant valleys in the north. One volcano, Mount Olympus, is three times as high as Everest, the biggest mountain on earth, and is as big as the state of Missouri. Valles Marineris is a huge canyon which would stretch all the away across the United States and is five miles deep in some places. There were clear signs –– dry lakes and river beds –– that water had once flowed on the surface of Mars, although there is no water there now. All of a sudden, Mars was a very interesting place! And it still is, even though the Viking spacecraft which landed in 1976 failed to find any signs of life in the top part of the soil.

But why would people want to go to Mars? Because it is part of the "final frontier" –– space. Almost everywhere on Earth has been explored, except parts of the deep ocean (which is almost as hard to explore as deep space). Mars is the only other planet in the solar system besides Earth that people might be able to eventually live on. Although Mars is cold, dry and nearly airless, it was once warmer and wetter. If we could find water in the rocks or beneath the surface, people could eventually make their homes on Mars, maybe within the lifetime of some of us living today –– maybe as early as 2030!

We are exploring Mars right now with robotic spacecraft partly to pave the way for humans. The Pathfinder landed on July 4, 1997 and sent out the little rover, Sojourner Truth, to explore. Pathfinder and Sojourner saw hills, a river valley, and rocks that might have been formed at the bottom of lakes.

Pathfinder also sent back data that gave us a sense of what it would be like to stand on Mars. First, although sometimes the temperature at the equator sometimes gets up to that of a crisp fall day most of the time it's very cold –– as cold as 150 degree below zero at night. Pathfinder's weather station found that the temperature would vary a lot from your head to your feet. Sometimes your head would be many degrees colder than your feet, and sometimes vice versa. These temperature differences result partly from the wind that swirls most of the time, sometimes kicking up dust devils. Sometimes the wind is fast enough to create giant dust storms that cover large portions of the planet, but the dust is so fine that the only effect on your view would be that the sky would be even pinker than usual. Yes, pink. Sometimes with blue clouds.

As you looked around the view would be stark but beautiful. The scientists have decided that the predominant color on Mars is not red, but butterscotch! There are many shades of gray, pink, dusky red and yellow. Rocks of all sizes and shapes stick out of the dusty soil. Unfortunately, you'd have to wear a space suit to protect you from the cold and provide oxygen, but it would still be a thrilling experience.

Mars Global Surveyor, currently in orbit around Mars, is picking up more signs that water used to exist on Mars. It's taking close up pictures of features which seem to be dry river beds and craters which once had lakes in the bottom. Mars Climate Orbiter and Mars Polar Lander are on their way to Mars and will get there on September 23 and December 3, 1999. Mars Climate Orbiter will measure the water still in Mars' atmosphere. The Polar Lander will dig into the soil near the South Pole and find out how much frozen water exists there. Mars Polar Lander also carries two little probes that will crash into the surface at hundreds of miles per hour and penetrate up to six feet. These probes, called Deep Space 2, will measure the temperature and water content beneath the surface. Future robotic missions are being designed to fly every 26 months, for 2001, 2003, 2005 and so on. If all goes well, we'll bring back the first sample of Martian rock and soil to the Earth in 2008.

Before we can send humans to Mars, we need to send scouts, just as the Native Americans like Sacajewea and the European explorers like Lewis and Clark explored the American west before the settlers moved in. In the case of Mars, though, the scouts will be robotic. So starting in 2001, the Mars missions will be trying to understand what dangers and opportunities future human explorers will face. The 2001 lander will measure the amount of dangerous radiation to determine if people would be able to build domes on the surface or if they will need to make their homes underground. 2001 will also try to find out if the soil of Mars is poisonous, and if we can make oxygen out of the carbon dioxide atmosphere so that future human explorers can make their own breathing gasses. 2001 will also carry Sojourner Truth's "sister" rover, Marie Curie, to repeat Sojourner's explorations at a new place on Mars.

Why else are we exploring Mars with robotic spacecraft? First, because we would like to find out what happened to Mars to see if the same thing could happen to Earth. When the solar system was formed four–and–a–half billion years ago, Earth, Venus and Mars were all pretty much the same: small, rocky planets. But Venus got too hot (the surface temperature of 900 degrees would melt lead), and Mars got too cold (a couple of hundred degrees below zero at night –– colder than anywhere on Earth). Earth, though, stayed "just right." Scientists even call it the "Goldilocks effect." Why did Earth stay warm enough so that liquid water could exist and not freeze or boil away? Could the climate change on Earth make our planet into a Venus or Mars?

Venus is so hot because it has a "runaway greenhouse effect." The greenhouse effect is why your car gets really hot with the windows rolled up when it's sitting in the sun. The sunlight goes in through the windows and heats up the inside of the car, but the heat can't get out through the windows because it is a different wavelength (color) than light. As a result, the car just gets hotter and hotter. The same thing can happen to a planet which gets a lot of carbon dioxide in its atmosphere, like Venus. The sunlight gets in and the heat can't get out. That is partly why several missions have been sent to Venus, to see whether we could cause a runaway greenhouse effect on Earth.

Mars, on the other hand, got so cold partly because it is 50 million miles further from the sun as Earth, and partly because it is smaller, so there is not as much gravity to hold the atmosphere onto the planet. Mars has no water on the surface today, and its atmosphere is very thin. If you were standing on the surface of Mars it would be like being at 100,000 feet altitude on Earth. Most people can't get enough air to breathe even at 20,000 feet, and water or ice can't exist where the atmosphere is as thin as it is on Mars. What little atmosphere that is left is almost all carbon dioxide –– no oxygen. So Mars is not a nice place to live right now.

Scientists think Mars used to be much warmer and wetter because the robotic spacecraft orbiting it have taken pictures of ancient lakes and streambeds. For water to have flowed on the surface long enough to make these channels, Mars would have had to have an atmosphere and been warmer than freezing. Now on Earth, anywhere there is liquid water there is life. Life began, the scientists believe, almost as soon as the Earth cooled down enough so that water would not just boil away into the atmosphere. Today there is life on Earth in boiling hot springs in Yellowstone Park and in deep ocean volcanic vents. Life can also exist where it's very cold, such as in the dry valleys of Antarctica –– inside rocks and in lakes under the ice.

So, if there was water on Mars, could there have been life? Scientists have examined meteorites that we know came from Mars and found chemicals which they think might show that life once existed on the red planet. If there is water underground on Mars, might life still exist? No one thinks that life on Mars ever advanced much beyond the algae or bacteria stage. No Martian civilizations are likely to have gotten started because Mars looks like it got too cold a couple of billion years ago. On Earth, it took several billion years for life to get beyond algae. But even algae on another planet would be exciting.

Right now, the only planet we know that has life is Earth. If we could find that life once existed on Mars, even very simple life, that would mean that life can get started in a variety of different conditions, not just on a small, watery planet 93 million miles from a small, yellow sun. And that would mean that it is much more likely that life exists out there in the universe among the billions of planets which must circle the trillions of stars. If life exists all over the universe, then there is probably intelligent life somewhere else –– maybe someone that we can listen to with our radio "ears," or maybe even talk to someday.

Whether we can find signs of past life on Mars (or even some struggling microbes living now) with robotic spacecraft or whether we need to send humans to explore is not yet known. If we do find signs of life, humans would have to be very careful not to kill it off or to contaminate the planet with our own kind of life. We really don't know what humans (or our future robotic spacecraft) will find on Mars. That is what exploration is all about.

The Mars Millennium Project was inspired by this same sense of exploration. It is important that every child be given the opportunity to explore the communities in which they live and gain a greater understanding of the wonderfully diverse elements that make it unique. By asking teams of children to design a livable community for the planet Mars in the year 2030, they must first identify all of the things that make their present community livable.

Through this interdisciplinary project, children will be exposed to the sciences, the arts, the humanities, and technology. In the process, they will see the intrinsic value that each discipline brings to their communities. So while preparing for the future, our children will be learning valuable lessons about the world in which they are presently living.

by Donna Shirley
Mars Exploration Program Manager
Jet Propulsion Laboratory (Ret.)