The Early History of Mars Investigations

 

1784  W. Herschel suggests that the bright patches seen at the poles are due to water ice.

 

 

 

1877  Schiaparelli describes long dark streaks as canali, Italian for channel. Although not implying intelligent origin, the term is quickly translated (in English at least) to be canal  an artificial structure.

 

1894  Percival Lowell established observatory in Flagstaff, Arizona.

 

1906  Lowell advanced extensive network of canals, which he believed were built by a race of intelligent beings. The dark regions were due to vegetation. (Earlier suggestions that they were standing bodies of water were shown to be incorrect through the use of polarimetry). Do to the nearly “full” phase of illumination, details of elevation were generally undetected, and Lowell (as well as many others) believed Mars was smooth. This would be required for a straight line canal network to be able to function.

The idea that Mars was inhabited become wide-spread, but not universal. Lowell’s own description of mars and its possible inhabitants, can be found in an on-line version of his book, Mars http://www.wanderer.org/references/lowell/Mars/. Then there is this page taken from a 1911 textbook on astronomy:

 

 

Lowell’s most vocal critic was E.M. Antoniadi. Although Antoniadi began with a general belief in canal-like features, gradually became more agnostic. During the close approach of 1909, his observations, made during long periods of spectacular seeing, convinced him the canals just didn’t exist. In a letter to Barnard he summarized his thoughts this way:

 

My general conclusion on the “canals” are:

 

I.               That the true appearance of the planet is a natural one

II.             That the geometrical network of Dr. Lowell is entirely non-existent; and

III.           That the so-called “canals” of Schiaparelli (and Schiaparelli only) do have some basis, - in this sense, that they are the optical products of very complex and irregular natural duskiness, sporadically scattered all over the Martian surface.

 

Photographic (left) versus drawn (right) images of Mars

 

R.S. Richardson, in his book Exploring Mars (1954), noted that “A perplexing (and irritating) circumstance is that professional astronomers with large telescopes are frequently unable to see canals, while amateurs with small telescopes claim they see them in abundance.” A few professional astronomers noted that under “moderate” seeing conditions, they saw canals, but under the best seeing, the canals broke up into disconnected dots. Clyde Tombaugh, the discoverer of Pluto, was absolutely convinced of their reality.

 

Now, there is a difference between saying that one can see “canals” and that they are real structures on the surface of the planet. The human eye/brain has the “ability” to form patters out of disconnected spots (perhaps to help us spot the creatures that wanted to eat us in our prehistoric days).

For a wonderful look at the history of this phase of the exploration of Mars, see the online book The Planet Mars: A History of Observation and Discovery by William Sheehan: http://www.uapress.arizona.edu/onlinebks/mars/contents.htm . Another good one is Mars: the Lure of the Red Planet, by William Sheehan & Stephen James O’Meara. Both are highly recommended.

 

Likewise, there was much debate concerning the possibility of life on Mars. Regardless of their scientific merits, the writings of Lowell, and the stories by H.G. Wells (The War of the Worlds  1898  see the online book: http://www.fourmilab.ch/etexts/www/warworlds/warw.html ) and Edgar Rice Burroughs (Princess of Mars  1911 - and others in the John Carter series) caught the imagination of the public.

 

Seasonal Color Changes  seemed to some to indicate seasonal changes in vegetation. It is suggested that lichens or some other primitive life form might be present on the surface.

 

 

Seasonal changes visible on Mars

What you see is also dependent on the wavelength, due to Rayleigh scattering in the atmosphere.

 

Mars at violet (upper left) and infrared (upper right) wavelengths.

San Jose as seen from Mt. Hamilton, in California, at the same wavelengths.

 

Spectroscopic Investigations of the Atmosphere

 

Lowell had published a report (unconfirmed by others) of the presence of water vapor in the atmosphere of Mars.

 

1934  W.S. Adams & T. Dunham place an upper limit to the abundance of O₂ in the Martian atmosphere of 0.1% that of Earth (1934, PASP 79, 308).

 

1947  Gerard Kuiper detects CO₂ in the atmosphere of Mars  being about twice that of Earth. However, many astronomers suggested that this paralleled the abundance pattern on the Earth, and that CO2 was a minor constituent. Gerard de Vaucouleurs (1950, The Planet Mars) suggested that the composition of the Martian atmosphere was 98.5% N₂, 1.2% Ar, 0.25% CO₂, <0.1% O₂. (He was wrong.)

Of course, the detection of water vapor was an exceedingly important goal.

 

 

 

 

Dust Clouds

 

Evidence reported sporadically in 1800’s. Strong support by Sciaparelli in 1877.

 

1909, 1924, 1956  Dust cloud envelopes most of the planet!

 

Dark Colors  The greenish regions of the otherwise ochre-red planet suggested the presence of vegetation to many astronomers, most (but not all of them!) unaware of the physiological effect of simultaneous contrast. This makes the appearance of colors dependent on the colors nearby them. But D.B. McLaughlin suggested a volcanic origin, with windblown ash being the source of the changes. Kuiper & Sharanov suggested it was the result of windblown dust.

You can read about the origin of the names for the albedo features in this paper: http://MartianNomenclature.htm