Demonstrating that the airplane can fly straight and level, turn when required, and ride out whatever turbulence may occur is the project’s primary goal. But the aircraft also has a 4.5-pound science payload consisting of cameras and—if room allows—a spectrometer for assessing the mineral content of rocks and a magnetometer (one of the great surprises to come out of the current Mars Global Surveyor mission is that some regions on the planet appear to have strong magnetic fields). The cameras will be able to spot details on the surface as small as six inches across. “If Mars has rabbits, we’ll see them,” jokes Levine.
Unfortunately, we on Earth won’t be able to watch live video of the mission because the aircraft can’t carry a radio powerful enough to send back that much data. Instead, it will send signals to the spacecraft that brought it to Mars, which will store them and send them back to Earth over a period of days. This is not a perfect arrangement, not least because the carrier spacecraft will be in line-of-sight communication with the aircraft for only 20 minutes of a flight that might last longer. But it should allow some images to come back, with at least one transmitted in real time. There will be some sort of show for Earthlings after all.
Some planetary scientists look on at all this unimpressed. They worry that the Mars Airplane will cost more than currently envisioned—$60 million was one outside panel’s estimate—and that what is basically a technology mission will start to eat into NASA’s science budget. Some would rather have used the first micromission opportunity for a communications relay satellite that could benefit other Mars exploration spacecraft with more ambitious research agendas. And some just don’t think it can be made to work. One scientist cites the Monty Python sketch about the difficulties involved in teaching sheep to fly: “The thing is, they don’t so much fly as plummet.”
But you can bet that if the Mars Airplane does fly, scientists will soon be queuing up to make use of its descendants’ ability to explore the Martian landscape. Once landing and takeoff are mastered—this aircraft will not try either—scientific instruments could routinely be sent to many sites during the same mission, making the investigations that much more productive. And aircraft could do things that no lander (unless extremely lucky) could ever do, like sniff out molecules given off by things living on or under the surface, if they exist. Because such molecules would be local, scarce, and short-lived, says Levine, they would probably be undetectable from orbit. But a search by aircraft (Dale Reed’s Mini-Sniffer again) could well find them. And although the existence of underground life would likely only be firmly established by drilling holes, a sniffer could at least show you where to drill.
The Mars Airplane is the first word in Mars aircraft design, not the last. “This is just the beginning of a generation of airplanes that will fly in the atmospheres of other planets,” says Levine. After all, if you can fly in the near vacuum of Mars, you can fly more or less anywhere. “Over the next 30 years we’re going to have many planes going to Mars, planes flying below the cloud layer on Venus to study the surface for the first time in visible wavelengths; we’ll study the organic haze on Titan; we’ll be sending planes to Jupiter and Saturn and looking under the clouds.” He points out that a recent report from the National Research Council concluded that mobility is not just important for solar system exploration, it’s essential. And mobility is just what airplanes promise.
The vehicles that make good on that promise will have all sorts of shapes and sizes. “There’s not one right way to make a Mars airplane, any more than there’s one right way to make an Earth airplane,” says Larry Lemke of NASA’s Ames center. Big sailplane-like vehicles may be good for some types of remote sensing. But if plans to manufacture rocket fuel from ingredients in the Martian atmosphere pay off, point-to-point mobility might be achieved with aircraft that use sheer speed to get around the difficulties of flying through a thin atmosphere, just as the SR-71 does on Earth. For other purposes, aerodynamically shaped dirigibles might be the way to go. The relative density of Mars’ carbon dioxide atmosphere makes lighter-than-air flight attractive; so does the fact that hydrogen, a better working fluid in every way than the helium used on Earth, will not burn in carbon dioxide. Give a big arrowhead dirigible a flat top and cover it with thin-film solar cells to generate power, and it could fly around Mars forever. Someday. Perhaps.
The Mars Airplane will bequeath technology to these far-off projects, but that may not be its major contribution. The Wright brothers changed not just the way we travel around the world but also the way we see it. Today all the images we have of Mars, save for those of three rocky landing sites, come from looking down at the planet. This orbital viewpoint, while wonderfully revealing, can’t help but turn Mars into a scientific specimen, a data set, a planet to study rather than a world to experience. The Mars Airplane will let us look out, not down, to distant horizons and what lies beyond them. It will let us watch our shadow moving on the rocks below as we fly through the sky. The camera in its rudder will show us the delicate banking of the aircraft’s wings as it heads off in directions no one has ever followed before. Long before human pilots fly over the Red Planet, these pictures may rekindle the romance of a new world in the audience back home.