ARISTARCHUS

23.7N by 47.4W

    LUNAR TRANSIENT PHENOMENA HISTORY

BY

DAVID O. DARLING

Aristarchus. "The brightest formation on the Moon-and the most 'active', since gaseous emissions have been proved, and the area including Aristarchus, Herodotus, Prinz and the Harbinger Mountains has been responsible for more than half the number of TLP reported over the years. As early as 1911 R. Wood, in the United States, took some ultra-violet photographs which led him to believe that a small area near Aristarchus was covered with a sulphur deposit, or at any rate something quite unlike the surrounding regions; this is still sometimes referred to as 'Wood's Spot'. The extreme brilliance of Aristarchus makes it obvious under any conditions, even when illuminated only by earthshine." Patrick Moore on the Moon

"Again, for a considerable distance to the north of Marius there is nothing much to see until we come to the close pair of craters, Aristarchus and Herodotus, and the neighboring serpentine valley, which together are an arresting sight at lunar sunrise. Aristarchus is the brightest spot on the Moon and is the center of a system of bright rays that straggle over the surface of the Oceanus Procellarum. The white bowl of this 29-mile crater is quite dazzling at the full phase. It is easily visible in even a small telescope on the dark part of the Moon early in the lunation when the Earthshine is bright. As previously mention, Aristarchus was once so brilliant that Sir W. Herschel thought he was seeing an active volcano. The shape of Aristarchus is somewhat polygonal. No other lunar crater of this size has such prominently terraced walls, which are quite massive, and there are many prominent spurs and buttresses. Perhaps the most interesting feature of Aristarchus is the system of dusky interior radial bands that run from the floor up the inner walls. Two or three of these are distinctly visible in even a three inch refractor but there are at least nine running  up the north, east and south walls and presumably up the west wall, which is tilted away from us owing to the nearness of Aristarchus to the limb." The Moon Observer's Handbook 1988 by Fred W. Price. 

 

LO4-150H.3 Lunar Orbiter 4 Photograph. (NASA)

The crater Aristarchus, when looking at my own observing experience could fill my own book on this subject. I have witnessed Aristarchus glowing in the Earthshine and have seen faint illumination inside the crater. This lunar formation has such a exceptional history when it comes to lunar transient phenomena that it dominates the entire field. I decided that since every kind of L.T.P. event has taken place here, this crater would be my first in-depth study. The following graph consist of data taken from the Lunar Transient Phenomena Catalog July 1978 NSSDC/WDC-A-R&S 78-05. The catalog was compiled by Winifred Sawtell Cameron  The publisher for this catalog is National Space Science Data Center (NSSDC) / World Data Center A for Rockets and Satellites (WDC-A-R&S) National Aeronautics and Space Administration, Goddard Space Flight Center Greenbelt, Maryland 20771. When looking at the data it is important to remember that sunrise does not take place until the twelfth day of lunation, so a great many of the reported events take place on the dark region of the Moon, between the second and fifth day old Moon. From the sixth to the tenth day, the sunrise terminator proximity to Aristarchus prevents observations of the dark portion of the lunar disk. Events have been reported in this time period and must have been exceptionally brilliant to compete with brightness of the lunar disk. The most interesting thing about this data is on day fourteen which is one day before Full Moon the lunar transient phenomena peaks out at thirty eight events. A detailed examination of the individual L.T.P. reports on this lunation date will give us a better understanding of what is taking place here.

Photograph shown below was taken using my 12.5 F 5 Newtonian reflector, with 12.5mm eyepiece and 2x Barlow. Using digital still camera DSC-P71 mounted for eyepiece projection. The photograph was taken on April 3. 2004 at 1:20 U.T.

 Photograph © 2004 by David O. Darling, Director L.T.P. Research

The learn more about Aristarchus region click here to view multispectral mosaic image taken by Clementine space craft. Mosiac. The false color image of Aristarchus shows different mineral deposits from a broader perspective, see false color. This image shows concentrations of iron located on the Aristarchus plateau, see Iron. To view Aristarchus image in true color go to real color. I have also included a series of drawings showing the appearance of the crater under different illumination. See Drawings. To look at the history of L.T.P. history for this crater can be checked here.

Graph © 2004 by David O. Darling, Director L.T.P. Research

The first graph represented all the lunar transient events reported for this crater. Due to the large number of events I decided to break them down into their individual classifications as given in the L.T.P. catalog. These five classification are Brightening, Bluish, Reddish, Gaseous, and Darkening. This will give the reader a better understanding of the dynamics taking place within this crater through out the lunation period.

This graph shows the distribution of the L.T.P. classification called brightening. As you can see this phenomena is mainly reported as an Earthshine event. The number of events reported on the graph for the fourteenth day are considerably less.

Graph © 2004 by David O. Darling, Director L.T.P. Research.

The lunar transient phenomena called violet or bluish as it will be referred to in this web site dominates the lunation on two specific periods. The first is on day twelve and second on day sixteen, with the Full Moon taking place on the day fifteen. 

Graph © 2004 by David O. Darling, Director L.T.P. Research.

The data indicates that the reddish events are reported at the time of lunar sunrise on this crater and  a second jump on the day after Full Moon..

Graph © 2004 by David O. Darling, Director L.T.P. Research.

The gaseous events is a special classification. This phenomena can be classified as a red or darkening event but if it behaves like a gaseous medium then both these classifications are given. Again the most active day takes place one day after Full Moon.

Graph © 2004 by David O. Darling, Director L.T.P. Research.

This graph reflects the lunar transient phenomena that is reported the least in association with Aristarchus. There are so few darkening events reported that it no significant pattern is revealed.

Graph © 2004 by David O. Darling, Director L.T.P. Research.

The graph below shows the phenomena broken down by its five basic components as listed in the Transient Phenomena Catalog July 1978 NSSDC/WDC-A-R&S 78-05.

Graph © 2004 by David O. Darling, Director L.T.P. Research.

    When looking at the lunar transient phenomena reports by months of the year, we find a continued increase until May then a drop. The month of July is spike may be caused by the landing on the Moon on July 20, 1969. At this juncture I have no explanation for the increase activity in the months of October and November.

Graph © 2004 by David O. Darling, Director L.T.P. Research.

The graph below shows the apparent brightness of the crater Aristarchus using the Santa Barbara CCD software by doing a cross section of the lunar formation going from the outside wall through the center of the crater then going to the outside wall again. I have done extensive measurements of the crater's albedo in attempt to document what changes take place throughout the period of lunation. The central peak of this formation is considered the brightest albedo feature on the Moon.

Graph © 2004 by David O. Darling, Director L.T.P. Research.

The next area of study is the whether lunar libration is a contributing factor for lunar transient phenomena. Since this study will consist of many graphs it will be located on another page. Click Here.