CHAPTER 2

LUNAR TRANSIENT PHENOMENA TYPES

 



The study of Lunar Transient Phenomena or L. T. P. is the study of short lived changes that take place on the Moon surface. The term Lunar Transient Phenomena as defined in the Anchor Dictionary of Astronomy means "short lived changes in the appearance of the lunar feature. These include reddish glows and obstructions of the surface detail that are triggered by lunar tides and occurs within lunar craters and around the perimeters of lunar basins. A carbon spectrum was obtain from an L. T. P. in the crater Alphonsus".


What physical appearance that L. T. P. takes on and the possible causes are much more involved beyond the brief explanation given by that dictionary. When looking at the different 
classifications of L. T. P. we get the following:

Gaseous: This is when the surface may appear diffused or nebulous. This effect can be tied in with Obscuration of the surface. It is believed that the obscuration may be caused by 
an out gassing from the interior of the Moon. This effect has been seen by many observers over the years in such areas as Mare Crisium basin, and the interior of Plato. I have seen this effect inside the craters Aristarchus, Tycho, and Plato.

Brightening: This effect can be associated with abnormal Albedo variances of lunar crater rims, or the extreme brightening of high Albedo features that for no apparent reason become even brighter. Features that been reported with this kind of phenomena are the rims of the craters Proclus, Censorinus, Aristarchus.


Darkening: This effect has been reported by observers on features such as Picard, and was witnessed by myself inside the crater Proclus. This can have the appearance of black ink. 
Some observers have reported that this blackness had the appearance of flowing across the lunar surface. This effect was also observed by myself over the crater Reiner, Picard and 
inside the crater Proclus. 

Bluish: The bluish effects are mostly reported on the darkened portion of the Moon when it is in crescent phase. Observers have reported features glowing with a bluish tint or in
electric arc blue. This takes place on the earthshine portion of the Moon. The most reported crater on the Moon for this kind of phenomena is Aristarchus. It has been reported many times over the years to be glowing bright in the earthshine region of the Moon while the entire earthshine portion of the disk is dusky and obscured with very few features being visible. 
(See Earthshine Observing Program.) This effect has also been observed during lunar eclipses of the Moon.

Reddish: This effect has been reported on the rim of the crater Aristarchus and inside the crater Gassendi. This effect can be detected using the Moon blink when viewing the Moon with Wratten #25 red and the Wratten #38a blue filters. When moving these two filters between the eyepiece and your eye you can get a blink effect. (See Conducting a Moon Blink)

Obscuration: This effect can be associated with out gassing and effect of the disappearing surface features. This has been reported in the crater Plato with the famous disappearance 
of the small craters on the floor. Others have reported large portions of the Mare Crisium basin to appear obscured with fine detail and small craters missing on the floor of Plato, while nearby features of similar size can be easily seen.


Shadow Effect: This is reported when the stark darkness or inky blackness of the lunar shadow is not there, but has taken on the appearance of dawn or dusk. The shadow is no longer black but gray in appearance. The shadow effect can also be associated with shadows being cast upon the surface when it is not expected to be any shadow visible. An example would be dark filled interior of a crater being observed but the sun angle being to high for any shadows to be cast inside it.


Contrast Effects: The effect can appear along the zone between the sunset and sunrise terminator or boundaries between light and dark. It can appear to be a graying effect or unusual appearance of the crater floor with in the light portion. This effect can be closely associated with the shadow effect, and obscuration.

Star-like Flashes: This is when the observers is surprised with brilliant flash that exploded in front of their eyes. These are most likely flashes produced by impacting meteor storm onto 
the lunar surface. When an observers see this kind of event striking the dark side of the Moon it will be burned into their memory for all time. So much interest has been generated by this
program that A.L.P.O has even established a new department dedicated to monitor for future impacts. See A.L.P.O. Observing program.


Star-like Lights: This is when a stellar point of light is observed on the Moon and can last for several minutes to up to an hour. These star like points are mostly reported by 
observers on the dark side of the Moon when the Moon is 3 to 4 days old. Star like lights have also been reported during total lunar eclipses.

Recurrent Lunar Phenomena (RLP): "There is a final aspect to consider, visual oddities that owe their origin to angle of illumination or phase of the Moon. For instance, the southernmost point of the northern peak of the central mountains of Gassendi exhibits deep red colouration during the period of approximately 18 to 24 hours after the terminator has receded. Cape LaPlace will display a dark shadow at the western (IAU) tip of its peninsula long after shadows in the region have been obliterated by high angle of illumination.  The crater Bullialdus has a feature on the west wall which casts a spectacular round shadow while the crater  is still under relatively high angle of illumination. Atlas, that has a depression in the inner southwest corner, throws an immensely black shadow just after local noon. There are uncounted traps for the unwary such as these, and for this reason the Section is listing these appearances as they are identified. For, perhaps, want of a better name the author decided to refer to them as Recurrent Lunar Phenomena (RLP), though of course they are not true phenomena." Guide to Observing the Moon British Astronomical Association Chapter 9 The Observation of Transient Lunar Phenomena by Peter W. Foley.

Other: This category represents the phenomena observed that does not reflect any of the above listing.