Why Martians? Mars is the nearest planet with a visible surface, and superficially looks Earthlike. It has seasons, polar caps, a similar axial tilt and rotation period, and surface markings that change with the seasons. It was natural to suspect the surface might be vegetated. Mars became a mythic arena for us to play out our fantasies.
The martial-sounding music used in the video is from a suite by Gustav Holst called The Planets. The selection played here is, of course, Mars. Holst wrote his music to reflect the mythological rather than scientific nature of the planets. In ancient times, Mars was the god of war (that's where the word "martial" comes from.) In the case of Mars, Holst explained that he was trying to depict the mindless stupidity of war.
War of the Worlds, written by H.G. Wells in 1897, was the first work of science fiction to depict really alien aliens; aliens with nothing in common with humans. The contrast to the complacency of Victorian England was startling. The video depiction of aliens focusing on Earth at ever finer scales violates the limitations of telescopic vision. Telescopes, no matter how perfect, simply cannot see details that small. That's why we have to send probes to the planets.
In 1938, a celebrated broadcast of War of the Worlds caused a nationwide scare, although no two authors agree on the actual extent of the scare, or whether the broadcast was interspersed with periodic disclaimers or not.
In 1877, the Italian astronomer Giovanni Schiaparelli announced that he saw canali on Mars. Canali means "channels" in Italian, but was promptly mistranslated into English as "canals" with the connotation of artificial origin. The American astronomer Percival Lowell was the most famous champion of canals on Mars. Eventually, detailed mapping of Mars showed that the canals did not exist except for one: Vallis Marineris.
Alfred Russell Wallace, co-discoveror of evolution, was one of the most prominent and accurate critics of the "canals", pointing out correctly that Mars was too cold and airless for canals to work. In addition, we now know that both polar regions of Mars are in depressions, meaning that water would have to run or be pumped uphill. Note the atrocious pun where Sagan refers to Martians making a "last ditch" effort.
Long after most astronomers ceased to believe in canals, popular books and periodicals continued to speculate on the nature of the canals. Similarly, long after astronomers had conclusive evidence that Venus was too hot for life, popular media continued to speculate on the possibility of life on Venus. The fantasy was simply more exciting than the reality.
Sagan puts his finger on the cause of Lowell's problem. When observing, one needs to put preconceptions aside. This is a subtle and difficult process. You have to be your own worst critic to make it work. As Sagan notes, "All in all, he believed too much" Nevertheless, for half a century the canals captured public attention. Edgar Rice Burroughs, also famous for the Tarzan novels, wrote a long series of novels about Mars as well.
|The psychology of Lowell's canals becomes clearer when we examine this 1896 map he made of Venus. Lowell had a penchant for seeing straight lines on just about every object he observed.|
The work of early rocket pioneers is detailed on another page. Goddard was influenced by Wells and Lowell, and on October 18, 1899, conceived the incredible plan of using a rocket to go to Mars. As Sagan notes, this was before anyone had ridden in an airplane or listened to a radio. Queen Victoria was still on the throne of England. Even more amazingly, Goddard and other early rocket pioneers lived long enough to see many of their visions fulfilled.
The limitations of long-distance reconnaissance are illustrated yet again by spacecraft studies of the Earth. Even from low earth orbit, there are few signs of life at 1 kilometer resolution, and only hints of large structures at 100 meter resolution. Early spacecraft imagery of Mars was utterly insufficient to rule out the possibility of life there. Even today, with imagery of Mars at the 10-meter scale becoming available, we can say there are no redwood trees, but nothing about small life forms.
One persistent myth is that the Great Wall of China is the only human structure that would be visible from the Moon. Although it's impressively long, the Great Wall is no wider than a typical two-lane road. Any major interstate highway is both wider and longer than the Great Wall, not to mention straighter and more contrasting with its surroundings. Interstate highways should be easier to see from the Moon than the Great Wall. However, neither would be visible to the unaided eye or even a fairly large telescope.
One enduring and noble misconception is that borders are invisible from space. Borders are easily visible; their very artificiality makes them obvious. Differing land-use practices on different sides of the border are the main reason. Along the California-Mexico border, for example, the U.S. side is much more vegetated than the Mexican side owing to overgrazing and cutting of wood for fuel in Mexico. Along the Maine-Quebec border, the Canadian side is farmed and settled but the U.S. side is forest land owned by lumber and paper companies. There are few emptier places east of the Mississippi and not all that many west of it.
There is no canal network. It does not exist. Schiaparelli may have been misled by optical illusions, but Lowell was certainly a victim of his imagination. As Sagan points out, the canals were certainly of intelligent origin; the only question was which end of the telescope the intelligence was on.
It's a pity that Schiaparelli and Lowell are remembered mostly for mistaken observations because both were skilled observers that did much useful work besides.
Lowell's canals are one example of an effect that has occurred several times in the history of science. Physicist Irving Langmuir called it the "threshhold effect". A strange and marvelous phenomenon is discovered on the very threshhold of observability. Now this happens often enough (after all, everything that is easily observable has already been discovered), but usually somebody soon discovers a way to make the phenomenon more observable. Real phenomena eventually lead to observational techniques capable of revealing them in detail. Unreal phenomena never do. Despite scientists' best efforts, nobody could ever quite get a clear photograph of a canal. Nobody can ever quite get telepathy experiments to yield consistent results, or get a really clear photo of Bigfoot or the Loch Ness Monster. The longer phenomena evade capture, the more likely it is they are imaginary. Eventually, most scientists, frustrated by the continuing lack of results, decide the phenomenon doesn't exist. The recent flurry of interest in "cold fusion" is a more modern example.
How can we know the ages of features on Mars ? Until we get rock samples back, we can only know approximately. The few Martian meteorites give ages that are very young by meteorite standards: a few hundred million to a billion years. Also, comparison of crater densities with the Moon gives an approximate idea of ages of surfaces
Viking 1 and 2 carried several experiments to detect life by putting Martian soil into possible nutrients and testing for metabolism. The results are ambiguous. The soil reacted vigorously with the nutrients, then tapered off in activity. Real metabolism would be expected to continue until the nutrient was depleted. Instead, it appears that something in the soil was depleted first. The conclusion of most scientists is that the reactions were due to inorganic chemical reactions. Ultraviolet light from the Sun can create highly reactive molecules that would produce results similar to those seen by Viking.
The Viking attempts to find life on Mars have sometimes been criticized for using search criteria that were too Earth-like. In reality, there were sound reasons for adopting the Viking strategy. For one thing, we know terrestrial biochemistry works. We have no real proof that any other kind of biochemistry even exists, much less what forms it might take. With no information to go on, a search for completely alien biochemistry would have been simply shooting in the dark.
Second, there are sound physical and chemical reasons for being, as Sagan puts it, a "Carbon-Water chauvinist". Carbon can bond to four neighboring atoms and bond to other carbon atoms, thus making it possible to form a vast array of organic molecules. Silicon, sometimes suggested as an alternative, does not bond easily to itself. (Boron bonds to itself, but only bonds to three neighbors, thus limiting its structural versatility, and boron is much ess common in the universe than carbon.) Water is a polar or asymmetrical molecule. It stays liquid over a wide range of temperatures. It attracts ions easily, making it a good transporter of nutrients, but does not dissolve organic molecules (so we do not dissolve in our own cell fluids). Liquid methane and ammonia, two commonly-suggested alternatives to water, are non-polar and lack many of water's useful properties. Thus there are sound reasons to believe life elsewhere will often be based on carbon and water.
The video shows the old stereotype of reducing a human being to the simplest chemical components. You can buy the exact number and proportion of atoms to make a human for only a few dollars. Likewise, you can buy the exact number and proportion of atoms to make a Lexus from a junkyard for only a few dollars. If you want to talk about the exact arrangement of the atoms, the price goes up sharply. Buying the exact organic molecules that make up a human would cost millions of dollars, and that's only the chemicals we can synthesize. There are many chemicals, like proteins, that we simply cannot synthesize as yet, let alone build a strand of DNA from scratch.
The crude but serviceable early Soviet technology visible on the Venera landers was a passing style. The Soviet Phobos missions were as elegant-looking spacecraft as ever flew. Unfortunately, they fell victim to typical Soviet thinking. Phobos 1 died of Chernobyl Syndrome ("let's cut corners and get the job done faster") when a ground controller ignored standard practice and sent a command without having it checked. There was one bad byte of data in it. It caused the spacecraft to lose its lock on the Sun, its batteries ran down, and by the time the error was discovered, the craft was dead in space. A spokesman for the Soviet space program said the guilty technician was not sent to Siberia, but he was also no longer with the space program.
Phobos 2 entered Mars orbit and was literally within sight of its goal, dropping a probe on the satellite Phobos, when it suddenly stopped transmitting. Soviet spacecraft had less redundancy than American craft, so if a major component failed, the mission failed. The former Soviet Union trusted its machines too much and its people not enough. Ironically, their chronic mistrust didn't keep human error from wrecking the Phobos 1 mission.
The Soviet Union had no monopoly on failed missions. The Mars Observer mission was going routinely and even sending back distant views of Mars when contact was abruptly lost on August 21, 1993. It is believed the retro-rockets exploded when they were ignited to put the craft into orbit around Mars.
Mars Pathfinder landed on Mars in the summer of 1998 and released a small rover, Sojourner (named for the Underground Railroad worker Sojourner Truth). The vision of a Mars rover shown in the video thus came to reality. Sojourner carried a video camera and geochemical analyzer. The spacecraft landed in an area where ancient floods had carried rocks from the Tharsis Plateau into the lowlands, enabling it to view a wide sample of Martian geology in a small area. It viewed possible water-deposited (sedimentary) rocks and found that the volcanic rocks had a lot more chemical variability than expected, indicating that the source of molten rock had been active for a very long time.
Mars Global Surveyor entered Martian orbit in November 1997. It used aerobraking, or repeated dips into the fringes of Mars' atmosphere, to settle into a low-altitude orbit, from which it will photograph most of Mars at ten-meter resolution. Because of a wobbly solar panel, the aerobraking is being done very slowly and cautiously, and Mars Global Surveyor will not settle into its final orbit until 1999. Meanwhile, it is already returning large amounts of high-quality imagery.
Sagan relates the moving story of his friend Wolf Vishniac, whose experiment was dropped from the Viking Lander. Vishniac died while attempting to detect life in the nearly lifeless Dry Valleys of Antarctica. Some of his apparatus, dubbed the "Wolf Trap", did indeed capture micro-organisms. However, Antarctica was once temperate and full of life. There is a vast difference between survival of a few life forms in a slowly worsening environment as opposed to evolution in an equally harsh environment
Enclaves are a common theme in science fiction; life holding on in a small spot on an otherwise lifeless world. However, change is the one constant in nature. On Earth, if a cataclysm destroys life in one spot, migrants from elsewhere rapidly recolonize it. But on a truly hostile world, such recolonization may be impossible. The environment in between may be too harsh, or there may be no air or water to transport organisms. When one enclave dies, it is not recolonized, and if a new favorable spot appears, nothing may be able to get to it. When the last enclave dies, that's it.
Hypothesis: if you don't find life almost everywhere on a planet, the planet is lifeless. Viking could have found life almost anywhere on Earth. My conclusion (I hope to be wrong) is that Mars is now lifeless.
The finer the geologic detail we see on Mars, the better the evidence that Mars once had a thicker atmosphere and more water, perhaps even glaciers. Thus, Mars could have had life early in its history.
In some parts of Antarctica, ice flows upward over obstructions and melts at the surface to expose ancient "blue ice". A rock on the surface here can only be a meteorite. The meteorites found here are treated with the same care as the rock samples brought back from the Moon and for the same reason: they are uncontaminated samples of other worlds. Some of these meteorites are identical to lunar rocks, others came from Mars. They were recognized as originating on Mars because gases trapped in the meteorites match the composition of the Martian atmosphere exactly.
On August 7, 1996, the National Aeronautics and Space Administration announced at a news conference that a team of researchers had found possible evidence for ancient life on Mars. The evidence was found in a meteorite, known by its catalog number ALH84001. The evidence for life consists of distinctive organic molecules called polycyclic aromatic hydrocarbons, microscopic nodules and crystals of minerals similar to those created by some types of terrestrial microorganisms, and very tiny spheres and tubes of calcite which have been interpreted as possible fossils of microorganisms.
On a number of occasions in the past, researchers have claimed to have found chemical evidence of extraterrestrial life, only to discover later that the chemicals were the result of terrestrial contamination. Thus, all researchers involved in studies of possible Martian life stress that they have discovered only possible evidence for life. They all agree that none of the pieces of evidence alone is definite proof for life. Nevertheless, supporters of Martian life feel that the simplest explanation for all the pieces of evidence together is biological activity. Skeptics say that there is not yet enough evidence to rule out non-biological origins for the features observed in the meteorites. Also, the supposed fossils are only about one-tenth as large as the smallest terrestrial bacteria and some critics believe it is not possible to have organisms that small. They claim that any system of organic molecules capable of growing and reproducing would require more space. (Viruses are smaller, but are not considered living because they cannot reproduce on their own but only within some other living cell.) The issue may not be finally resolved until samples are returned from Mars by future space missions.
Terraforming is the hypothetical ideal of transforming a planet to make it habitable for humans. We are not yet able to do this on anything like the scale it would take. Terraforming Mars would involve releasing water and creating a thicker atmosphere to be breathable and to retain heat. Genetically engineered plants have been suggested as the best way to begin the process.
If Mars has life, even microscopic, our policy should be to leave it alone. An example of extraterrestrial life would be so important to our understanding of biology that destroying it would be unconscionable. Would we still feel the same way in centuries if Mars has only one or two microscopic life forms that could be preserved in a Petri dish, or after we know of dozens of extraterrestrial life forms? I don't know. But even if Mars is lifeless, do we want to transform a world with such scenic wonders?
What would it be like to be on the receiving end of terraforming? Science fiction author David Gerrold, best known as author of the famous "Tribbles" episode of Star Trek, has a four-part novel series, The War Against the Chtorr, dealing with an alien transformation of the Earth. The series is still incomplete, but it's not looking good for the home team so far.
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Created 13 January 1998, Last Update 17 March 1998
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