Ever since Italian astronomer Giovanni Schiaparelli sketched precisely measured maps of Mars in the late 1800s, and dubbed some of the channel-like features "canali," no planet in our solar system has gripped the human imagination more tightly.
Canals implied water. Water implied life. Mars quickly became the focus of popular lore, from H.G. Wells's "War of the Worlds" down through last summer's movie "Red Planet."
Now, scientists are about to move a step closer to answering questions about what really does - and once did - exist on the mysterious planet.
Tomorrow, the United States is set to launch an orbiting prospector that will scour Mars for evidence of water, both past and present.
The probe will not only help satisfy scientists' curiosity about one of the great mysteries of the solar system, but could also provide a needed boost for NASA, under fire for cost overruns on the International Space Station.
The craft, Mars Odyssey 2001, is designed to build detailed maps of minerals on the Martian surface. Those deposits will help planetary geologists reconstruct the history of water on the planet, as well as the processes that sculpted the surface. The orbiter, which looks like a backpack with wings, will also remotely probe the first meter of Mars's surface for water ice.
If Schiaparelli wouldn't recognize micro-chip mapping tools, he would recognize the questions driving the $297 million mission.
"Did Mars harbor an environment hospitable to life? If not, what was there?" asks James Garvin, Mars program scientist at the National Aeronautics and Space Administration in Washington.
When the Viking program of the mid 1970s attacked the question of life on Mars, its two landers came up empty-handed, he notes. The landers and their parent orbiters presented what he calls the "old Mars" of lifeless polar deserts. Mars Odyssey will orbit what he calls "the new Mars" revealed by the Mars Global Surveyor, now in orbit.
"We see sediment layers and seepage gullies that raise challenging new questions," he says. Indeed, Mars Global Surveyor has beamed back images of terrain that in places look like the setting for a John Wayne western. The only thing missing from the earthly-looking buttes are Pinons and sage brush.
The seepage gullies in particular have generated debate among planetary scientists. Some argue that near-surface water-ice deposits may warm, melt, burst from canyon or valley walls, and then flow down to the floors.
Other researchers say the flows may stem from subsurface carbon dioxide, which liquifies under the low temperatures and high pressures beneath the surface. The CO2 can escape with enough force to etch the gullies before it vaporizes, these researchers say.
The difference is crucial to mission planners hoping to identify places a lander or rover might search for water.
Moreover, an analysis of Mars Global Surveyor data in yesterday's issue of the journal Nature suggests that features once considered coastlines in an old oceanic plain may be wrinkles that rose when expanding crust put the squeeze on the area. If coastlines aren't really coastlines, was there ever an ocean there?
Mars Odyssey carries two instruments that could help settle such questions. Its thermal-emission imaging system is designed to scan the surface for visible and infrared light reflected from rocks and soils. The infrared detector should pick up deposits of minerals such as carbonates, silicates, sulfates, and phosphates, which form in the presence of water.
Yellowstone-like hydrothermal deposits also should show up, if they exist. And researchers say that the infrared portion of the imager has sufficient resolution to spot any active hot springs during a Martian night.
The imaging systems' visible-light detector, which can spot objects as small as 18 meters across, will be combined with the mineral map to pick potential landing sites for future Mars missions. In addition, Mars Odyssey carries a gamma-ray spectrometer that will look for concentrations of hydrogen in the upper meter of Mars's surface.
The craft's package is topped off with a radiation detector whose data will be used to assess the hazards to humans should manned Mars missions ever be launched.
Beyond science, the Mars Odyssey is "the lead-off batter in NASA's new approach to Mars missions," says Scott Hubbard, Mars Program director at NASA headquarters.
The agency is still smarting from the loss in space of two back-to-back Mars missions, which NASA officials acknowledge resulted from overly zealous adherence to the faster-cheaper-better mantra of the past decade. A new management team, more rigorous reviews and testing, and enough money to do the job without cutting corners are among the changes the agency has adopted.
Now, "each mission does something for the success of the next," Mr. Hubbard says. Mars Odyssey, for example, will remain in orbit to act as a radio relay station for missions such as the twin-rover project slated for 2003. Another orbiter is scheduled for launch in 2005.
Hubbard notes that out of 34 attempts to reach Mars among all spacefaring nations, the global "batting average is .330," although the US alone is hitting .600.
But other teams are trying to improve their standings. Japan is working to launch a Mars orbiter in 2003, when the European Space Agency plans to launch a lander. And British researchers recently have proposed an ESA Mars mission for 2009.
(c) Copyright 2001. The Christian Science Monitor