Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 1/18/85; site seismo.UUCP Path: utzoo!watmath!clyde!bonnie!akgua!gatech!seismo!rivers From: rivers@seismo.UUCP (Wilmer Rivers) Newsgroups: net.astro Subject: Re: Canals on Mars? Message-ID: <970@seismo.UUCP> Date: Tue, 12-Feb-85 08:53:17 EST Article-I.D.: seismo.970 Posted: Tue Feb 12 08:53:17 1985 Date-Received: Thu, 14-Feb-85 00:53:48 EST References: <1137@sunybcs.UUCP> Distribution: net Organization: Center for Seismic Studies, Arlington, VA Lines: 29 > From the Associated Press: > > SAN FRANCISCO - Water on Mars vanished after carving the famed canals > 3 billion years ago, and scientists say discovering where it went will > help them find drinking water for earthlings who someday may colonize > the Red Planet. > > The canals are 2,000 to 3,000 miles long and 1,000 feet deep. Schiaparelli's (1877) canals, made famous by Percival Lowell, were about this long, but no depth can be attributed to them, since in fact they did not actually exist. As Michael Carr writes in "The Surface of Mars", "...the canals appear to be largely an imaginary perception on the part of the observer of irregular groups of surface markings close to the limit of telescopic resolution." The AP report appears to be confusing these non-existent "famed canals" with 2 other features which really do exist : the immense system of connected canyons (originally called the Coprates Canyon, now the Valles Marineris) just south of the Martian equator, and the much smaller networks of erosive channels, at least some of which once contained running water (however briefly - perhaps in a flood). The canyon system, which appears to have been formed by collapse rather than by running water, is a total of 4000 km long and is 7 km deep in places. The channels, on the other hand, show signs of flowing water (or ice, or in some cases lava), but they are only tens of km long, sometimes connecting to 300-km long networks, although certain fluvial features extend about 2000 km (these last are outflow features from catastrophic floods rather than remnants of long-lived drainage). The reporter seems to have been less than clear in the distinction.