When President Bush announces an ambitious plan on Wednesday to send astronauts back to the moon as a stepping stone to a manned Mars flyby, many may wonder why not aim for the Red Planet directly.
One big reason is practice. Many scientists believe that before astronauts attempt to reach Mars, a so-called "camp site" on the moon is needed to test out transportation and survival capabilities.
The moon is an average 250,000 miles from Earth — a stone's throw compared to the average 48 million miles that separate our planet and Mars. There are many critical questions about surviving on a hostile surface that still need to be addressed, such as radiation exposure, microgravity concerns and keeping up supplies of air, food, water and energy. Most believe it's best to figure out these issues from a place that's closer to home.
As a 1992 NASA report states, "the relatively accessible moon affords valuable experience in living on a hostile planetary surface while still maintaining the option to return quickly to Earth in an emergency."
Getting to Mars, even in a fly-by mission, is a grand goal that's "surpassingly fascinating and desirable," says Harley Thronson, director of technology in the Office of Space Science at NASA headquarters in Washington. But, he adds, "It's virtually certain we would need an intermediate step like the moon to get there."
Here are some key factors scientists need to address to establish a lunar base camp and a subsequent manned trip to Mars.
According to a May 1992 NASA report, nuclear energy could offer powerful propulsion for the heavy-lifting that will be required to carry the significant supplies for setting up camp on the lunar surface. It will also be critical in cutting the traveling time to Mars and reducing travelers' exposure to dangerous radiation.
Among the most critical worries facing lunar inhabitants and Mars explorers is exposure to cancer-causing doses of radiation. Radiation from solar flares or cosmic ray "storms" can last for days and astronauts could be exposed to massive doses since they will be spending record time in space.
To protect humans in space, scientists will need to improve their ability to predict space weather and solar storms, as well as develop safe, shielded vessels. Once warned, explorers could take refuge in shielded capsules in spacecraft or in underground bunkers on the moon or Mars.
Any spacecraft or habitat must have adequate air suitable for human breathing. One important aspect of maintaining breathable air is establishing recycling systems that remove carbon dioxide and contaminants.
On lunar and Mars surface camps, explorers could possibly establish a steady oxygen supply by mining minerals from soil and extracting elements needed to create oxygen.
For a moon outpost or a Mars journey to be feasible, explorers will need to grow most of their food supplies. This could involve building greenhouses for growing vegetables, and possibly even developing meat products in laboratory nutrient solutions.
In order to manage human waste and other waste, extreme recycling will be required. Astronauts on the space station already use systems to recapture water from their urine and perspiration. Solid human waste could be treated and used to fertilize greenhouse products. It will also be important to recycle any supplies that have served their initial purpose.