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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.