A similar but smaller patch was apparent to Schiaparelli at the same opposition of 1879. This one which he styled the Nix Atlantica lay between the Thoth and the Syrtis Major. It was about half the size of the Nix Olympica and has never since been seen, though it should have been had it continued to be what it then was.
White in Elysium.
On the other hand, phenomena of the sort undetected of Schiaparelli have been remarked at Flagstaff. On May 18, 1901, I was suddenly struck by the singular whiteness of the southeast corner of Elysium where that region bordered the Trivium. Elysium has a way of being bright but not with such startling intensity as this spot presented nor in so restricted an area as was here the case. The spot was so much whiter than anything I had ever previously seen outside the polar caps that it arrested my attention at once. And this the more that I had observed this same part of the planet the day before and perceived nothing out of the ordinary. Once detected, however, the spot continued visible. The next day it was there with equal conspicuousness, and now thrust an arm across the Cerberus, entirely obliterating the canal for the space of several degrees. In this salience it remained day after day till the region passed from sight, to reappear with it six weeks later when the region again rounded into view. The hour of the Martian day seemed to make no difference in its visibility. It was seen from early morning till Martian afternoon, as late as the phase permitted. Clearly there was nothing diurnal about its revealing, and it lasted for at least three months and a half, until the planet got so far away that observations were discontinued.
It was to all appearances and intents snow. But now comes the singular fact about it. It lay within ten degrees of the equator and showed from the end of June to the latter part of August. To our ideas there could be no more inopportune place or time for such an exhibition. For it cannot have been due to a snow-capped peak, as we know for certain that there are no mountains in this, or in any other, part of the planet. Besides, it had not appeared in previous Martian years; which it infallibly would have done had it been a peak. Indeed, it baffles explanation beyond any Martian phenomenon known to me. It seems directly to contradict every other detail presented by the disk.
The phenomenon is thus unique in kind; it is not, however, unique as a specimen of its kind. The eastern coast of Aeria where that region borders the Syrtis Major is prone to a brilliance of the same sort. It is a narrow belt of country that shows thus, nothing but the coastline itself, but this for a considerable distance stretching several hundred miles in length. It has stood out saliently bright now at every opposition which I have observed, beginning with 1894. Sometimes it has been described in the notes as bright simply, sometimes as white, and once, in 1901, as glistening at one point like ice. Yet when upon the terminator it has never stood forth as a mountain range should have done to declare its character.
It has been evident regardless apparently of the Martian season. In 1894 it was bright from October 25 to January 16 (Martian chronology); in 1896, from December 22 to January 7; in 1901, from July 13 to the 15th; in 1903, at about the same date and so in 1905. It was whitest during the latter oppositions, showing that the effect is most marked in its midsummer. All of the above instances of extra-polar white have been located within the tropics. Examples of the same thing, however, occur in the north temperate zone. Tempe, a region just to the west of the Mare Acidalium, is exceedingly given to showing a small white spot close upon the Mare’s border in latitude 50° north. This spot, too, on occasion glitters as it were with ice. It is also at times very small. So that whereas much of Tempe is by nature bright but a small kernel of it is dazzling.
The list might be easily extended from the record book. Thus on March 1 and 2, 1903, the disk showed speckled with minute white spots, one in Arcadia in latitude 41° north, one in Tharsis near the equator, a third just north of the Phoenix Lucus in 10° south, and a fourth, the Nix Olympica, and on April 11, a glittering pin-point starred like a diamond the centre of the Pons Hectoris. On both these occasions the Martian season was summer; July 9 for the latter, June 21 for the former date.
White in the Pons Hectoris.