Don’t Believe the Hyperbole
It is easy to remind ourselves not to believe everything which is confidently declared as fact, but it is quite another to actually follow that good advice. How many generations of English students, for example, have memorized Shakespeare’s ominous declaration in Merchant of Venice: “All that glitters is not gold–/ Often have you heard that told.” (Act II Scene 7). Even today however, centuries after Shakespeare’s time, we all too often believe appearances, whether they be objects for sale or statements of scientific fact.
Just about everybody has heard, for example, that the geology of Mars bears ample testimony to that planet’s watery past. Most people consider this a fact. Some recent articles on the topic however, demonstrate that this may not be the case.
The main evidence for the alleged watery past of Mars is circumstantial. A recent commentary in the journal Nature for example pointed out: “That water once flowed on the surface of Mars seems clear from decades of awe-inspiring spacecraft images of valley networks and giant fluid-carved channels.” (Dec. 22/29/05 p.1087).
Thus encouraged by appearances of past erosion, several nations co-sponsored orbiting spacecraft to search, by means of remote sensing techniques, for signs of water-altered minerals. If there had been water at one time, such minerals should be present.
For decades, such searches failed to find definitive traces of clays, carbonates or sulphates. For example, during the final stages of evaporation of large seas or lakes on earth, substantial carbonate salts are deposited on the sediments. If such an ocean once existed on Mars however, the drying up of this body left no carbonate signature.
Finally in the late 1990s, a machine on board the orbiting Mars Global Surveyer, identified small patches of the mineral haematite. Generally this mineral requires water to form. This discovery was thus taken as a good sign. But where were the clays? These minerals should be widespread.
The Mars rovers were dispatched to find these and other evidences of the past presence of water. Finally a scientific team reported the scattered presence of phyllosilicates, clay minerals with a layered structure (Nature. December 1/05 p. 623) These clays were found in the cratered highlands of Mars and they were taken to indicate that Mars was wet at an early stage in its history.
The scientists proposed that shallow highly acidic bodies of water existed between sand dunes, and that various episodes of higher and lower water levels led to the precipitating of haematite and other minerals. Less than three weeks later however, two papers were printed (in Nature) which challenged the idea that water was present when these minerals formed. The paper by McCollom and Hynek (December 22/29/05 pp. 1129-31) proposed that these minerals formed at high temperatures from explosively released volcanic ash. No surface water was required, just some water vapour in the volcanic release.
The other paper in the same issue (Knauth et al pp. 1123-1128), proposed that a ground-hugging turbulent flow resulted from the impact of a meteor. The outcome of such an event could very well resemble the land forms and minerals produced on earth through the action of water. It is evident that the presence of these minerals does not prove that water was ever present on Mars since other reasonable interpretations of their formation are possible.
A commentator in this issue of Nature (p. 1088) concludes that it may well be that Mars never had the water needed to harbour life or origin-of-life processes. It is traces of life, after all, not just water, that the scientists really want to find on Mars.
An astute reader will notice that the journal Nature printed three papers within a month, all of which drew different conclusions. There is nothing wrong with this. It is good to examine an issue from different points of view. The problem comes when the media report one conclusion or other as fact. The lesson in all of this is, don’t believe all the “everybody knows” pronouncements about Mars or any other issue. Find out the details.
In the case of Mars, no one has yet demonstrated that large amounts of water were present on that planet. Maybe there was water there, or maybe there wasn’t. We do not yet know and possibly may never know. Just don’t get swept up in the rhetoric on this or any other issue.
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