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|Hubble photograph of Mars, 3/97, NASA|
When astronomer Gioavanni Schiaparelli saw fine cobweb-like patterns on Mars, he thought they looked like grooves or "channels". Writing in Italian, he marked them Martian "canali". It wasn't long before newspapers applied questionable translation skills broke the story of the Martian "canals".
Turn of the century scientists like Percival Lowell concluded these clearly artificial features must signs of intelligent life drawing precious water from the poles. Surely only a global catastrophe could warrant such massive public works. The Martians must be a very ancient race of great technical prowess. What must they be thinking as they look at Earth's great oceans while their own world lay dying?
Thus was born the Mars of classic science fiction writers like H.G. Wells, Edgar Rice Burroughs, and Ray Bradbury. It was a Mars filled with life that man would meet one day. To Wells, the encounter came by Martians invading Earth. Burroughs imagined his hero, John Carter, magically teleporting himself by sheer force of will onto a planet of beautiful Martian princesses and giant, four-armed Martian savages. However, it was Bradbury who created the most memorable Martians. They were wise and cultured, but unprepared for humans and their rocketships. Quickly, they died out, leaving behind a wondrous world to explore and cultivate. The humans who came look at their faces reflected in the broad canals and realize that THEY were the Martians now.
It was not to be, of course. In time, photographic film grew faster and astronomers could take accurate pictures without resorting to artistic license. The canals vanished. What's more, the first close-up pictures of the Red Planet taken by scientific spacecraft showed a barren and desiccated world with few changes apparent in the last billion years. True, there were gorges, river planes, and other signs that great water flows had made their mark in the distant past, but there were no signs of running water today.
It was more than surface features that told scientists Mars was dry. We learned that the air pressure there is so thin that water on the surface can not exist as a liquid. Warmed, it turns to vapor. Cooled, as it is at the Martian poles, it forms into frosty ice crystal. With wetness precluded by basic physics, Mars could only be drier than the most severe deserts of Earth.
More out of personal conviction than scientific evidence, some still held out hope that life is lurking in the Martian soil. In 1976, the twin Viking landers looked there and scientists rendered their verdict -- the majority declared Mars was dead and may always have been. Science fiction writers will just have to get used to it.
Some writers, like Frank Herbert in his Dune novels, adapted the tradition by moving their vision of Mars to undiscovered worlds. Others, like Kim Stanley Robinson, imagined a Mars "terraformed" by Man into a new Earth. So science fiction was once more in step with science -- or so it seemed.
As anyone who has ever dug a well can tell you, just because your topsoil is dry doesn't mean there isn't water underneath. On Mars, the weight of soil could allow subsurface water to flow, providing it's the right temperature and deep enough. A shallow well wouldn't do since calculations show that you'd have to go down a kilometer or more for conditions to be right. Still, that offered some small prospect of finding supplies for future human settlements.
Last month, high-resolution pictures from the Mars Global Surveyor spacecraft were shown to the public and they unraveled all previous thinking about Martian water. They showed small channels cut on the sides of cliffs where landslides had recently occurred. To Earthbound eyes, they appear to have been cut by water. If they were cut by water, it had to spring from no more than 100 meters below ground before evaporating on the surface. Best of all, 100 meters is easy reach for a good well digger.
Much will be written about Martian water in years to come - whether it really is there and if it is how much. Some will write about what can be done for human explorers freed from having to carry all their water with them. For me, I'm just pleased to reflect how rapidly our expectations changed from a "wet Mars" to a "dry Mars" and back to one that might actually be damp in spots.
It can happen in the blink of an eye.
It is human nature to want to forget our mistakes, and to remember only our successes. Looking at the NASA Mars exploration site for example would lead us to believe that the Mars polar orbiter was the first Mars mission ever to fail. This couldn't be more wrong!
Named aptly after the god of War, Mars seems to want to keep it's secrets. Spacecraft have been launched toward Mars from as early as 1960 when the USSR launched 2 probes intended for a Mars flyby. They failed to reach earth orbit. Although the Soviets had incredible successes with their Venus probes, They seemed to have suffered a curse when it came to Mars. Three Mars probes launched in 1962 failed to leave earth orbit, and a third, Mars 1, lost contact with earth en route to Mars.
The U.S. had better luck in 1964 when Mariner 4 made the first successful Mars flyby; however, this was only after Mariner 3 had a booster failure. The same year, Zond 2, a Soviet probe, lost contact with earth en route to Mars.
Mars was dropped as a target until 1969 when Mariner 6 and 7 made successful flybys sending pictures back to earth. The USSR also launched two probes that year, but they failed.
The Soviets tried again in 1971 with three probes: Zond 419, Mars 2, and Mars 3, Mars 2, launched May 19, 1971, successfully reached Mars orbit, but failed during a landing attempt. This was also the case for Mars 3, launched days after Mars 2 on May 28. Mariner 9 beat them both to Mars, making the first Mars orbit even though it was launched later (on May 30). It did not have a landing planned, and successfully completed a photographic mission.
In 1973 the Soviets launched four more Mars probes, Mars 4-7. Mars 5 became the fifth craft to orbit Mars. Mars 4 flew by after a retro rocket failure. Mars 6 lost contact before its capsule could land, and Mars 7 missed the planet entirely.
U.S. successes occurred again in 1975 when Viking 1 and Viking 2 had the first and second successful Mars soft landings. They gave us our first pictures of the Martian surface.
Other Mars probes have been launched with similar records. The 1997 successful pictures from Mars Pathfinder, came after the failure of the Mars 96 probe. Launched from Baikonur on the 16th of November 1996, It failed to leave Earth orbit, crashing down between Easter Island and the Chilean coasts.
It was easy for us as Americans (especially during the cold war) to say that these failures were due to shoddy Soviet workmanship in the face of superior American know-how, but to believe such propaganda is to ignore the basic fact of these statistics. The fact is that Mars is hard to reach. Harder than we like to acknowledge. What do we really know about Mars? We know its orbit, its gravity, its surface pressure, its atmospheric composition, and its lack of a strong magnetic field. We also have some nice pictures of it. If this kind of knowledge were all that we had of the Earth, how many probes would we loose exploring it? How many would land in bogs, or get buried under rock slides, or descend into a hurricane before we had a successful landing.
Tallying up our successes and our failures, I think that you'll find that the failures outweigh the successes. This doesn't mean that we should give up and forget Mars. It only means that we cannot take it for granted. Until we learn to treat it with respect, Mars will remain mysterious and unknown.
References: Wilson, Andrew Solar System Log, 1987. Jane's Publishing Company. NewYork.
The infospace developing group (website) http://www.iki.rssi.ru/mars96/mars96hp.html
Why would we want to live on Mars or the Moon? For colonists, the answer can be summed up in the term "resources". For Earth, the resources are obvious: a large, wet biosphere with ample biological materials which are in turn supplied by an ample inventory of volatile chemicals: water, oxygen, carbon dioxide, and so on.
For the Moon, these things are missing. Of material resources, there are really only a lot of metal oxides. On the other hand, the real resource of the Moon is its location -- on the surface of the Moon you are practically in space! Single-Stage to Orbit (SSTO) is not only possible, it isn't even difficult. We did it successfully in 1969 when the Apollo 11 LEM ascent module, which was only about the size of a delivery van, lifted off. Compare that to the Gemini-Titan vehicle that was designed to do that same job (that is lift two people and small collection of supplies) from the Earth -- a three-stage vehicle which altogether weighed about the same as ten semi-trucks!
What Mars gives us is "the best of both worlds": although there is no large biosphere, Mars does give us all the volatiles and other chemicals we need to provide small ones for ourselves.
Recent spacecraft studies have increased the evidence for large supplies of subsurface water ice on Mars, and we already knew about substantial quantities at the poles. The atmosphere provides a ready medium for early mining of simple volatiles like carbon dioxide and argon (as well as traces of water, nitrogen, and oxygen, although these are really small traces on Mars), which may be very useful for early colonization, although mining solid state resources will probably dominate in the end.
Nevertheless, Mars is not so difficult to escape as the Earth -- compare the orbital velocities of the three worlds:
As you can see, Mars' orbital velocity is about midway betweenthe two, slightly favoring the Moon! After folding in the effect of the atmosphere, which is only about 0.5% of Earth's in pressure, it's clear that SSTO from Mars is much easier than from Earth, if not quite so easy as the Moon. I haven't actually done the calculations, but it seems likely that a vehicle not much different from the DC-X test vehicle could be a successful Mars to orbit shuttle, despite being far from being able to do this on Earth.
Then there's the moons: Unlike the Earth, Mars provides very convenient natural harbors in the moons Phobos and Deimos. The gravity on these moons is just enough to be useful, while not at all impeding what you can do there (a small amount of gravity will tend to remove dust and debris from the air, for example, without putting much limitation on what you can lift, so long as you don't lose control of it!). And, there is enough material there to use some of it in construction instead of hauling everything up from Mars (let alone Earth). These will always be more convenient than the "artificial harbors" (like Mir and ISS) that we are forced to use in Earth orbit. The Moon is perhaps a candidate for this, but is really more like another world.
The surface of Mars is also a psychological resource. The bright sky of Mars is much more homelike than anything space colonists will find in space, and contributes to the "wide open spaces" feeling that Mars has compared to places like the Moon (and other moons in the solar system). And there are wide open spaces: Mars has about as much land area as the Earth (since there is no ocean area). Furthermore, Mars' atmosphere (especially the ionosphere), while not offering complete protection, does shield you from some of the more dangerous radiation (which is not true on the Moon). It's true that the coloring of Mars is sadly lacking in blues and greens, but we will be bringing plants, anyway!
Someday this combination of lifestyle with economic convenience may make Mars the real center of economic power in the solar system (more so than even the Earth), if we can but overcome the obstacles to establishing ourselves there.
Next month we'll focus on the Outer Solar System. Especially the moons of Jupiter and Saturn.
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