One of the problems with lunar photo's have always been the extremely poor resolution of photograph's that NASA released over the years. While in the Army, I have seen some very high resolution photographs taken from military "sources", so I know that the ability to see high resolution is not lacking, only the photo's that NASA has been willing to release is ... lacking. Now, on to LTP's.
Reprinted from Sky & Telescope Magazine, March, 1991.
LUNAR TRANSIENT PHENOMENA (LTP)
by Winifred Sawtell Cameron,
On January 24, 1956 amateur lunar observer R. Houghton was drawing the crater Liebig on the edge of Mare Humorum when something bright flashed in the field of his 7-inch telescope. The flare came from the nearby crater Cavendish, which was just emerging from the lunar night. Closer inspection revealed that a peak on the crater's eastern wall was repeatedly flashing.
Houghton called astronomer Brian Warner and told him what to look for. Warner too saw the flashes and called them "so conspicuous that they were seen immediately." The other peaks in the vicinity remained normal.
On the night of November 2-3, 1958, Soviet astronomer Nikolai A. Kozyrev witnessed a strange phenomenon while making spectrograms of the crater Alphonsus with the Crimean Astrophysical Observatory's 50-inch reflector. As he watched through the telescope's guiding eyepiece, he saw the crater's central peak blur and turn an unusual reddish color. The spectrograms confirmed his visual impressions of a volcanic event; they showed an emission spectrum of carbon vapor (S&T: February, 1959, page 184).
On July 19, 1969, the Apollo 11 command module had just achieved orbit around the Moon when the Mission Control Center in Houston, Texas, received word that amateur astronomers reported transient phenomena in the vicinity of the crater Aristarchus. Asked to check out the situation, astronaut Neil Armstrong looked out his window toward the earthlit region and observed an "area that is considerably more illuminated than the surrounding area. It just has -- seems to have a slight amount of fluorescence to it." Although he wasn't sure, Armstrong believed the region was Aristarchus.
Accounts of lunar transient phenomena (LTP'S) are not new. Over the past 30 years, I have collected close to 2,000 observations dating from as far back as 557 A.D. Most are visual reports of bright spots, flashes, hazes, and curious temporary colorations of the lunar soil. Reputable observers such as William Herschel, Wilhelm Struve, and E. E. Barnard have seen them. Some LTP's have even been photographed, as well as recorded polarimetrically, photometrically, and spectroscopically. Yet, despite a profusion of observations and six Apollo missions to the Moon, the nature of LTP's remains elusive and their origin an enigma.
About 200 of some 30,000 lunar features visible in telescopes have been recorded as LTP sources. Half have shown activity only once. Of the remainder, a mere dozen features contribute three-fourths of all reports. One area, Aristarchus-Herodotus-Schroters Valley, is responsible for fully one-third of the total number sighted.
Most LTP activity occurs along the edges of the maria, near volcanic features, like domes, sinuous rilles, and craters with dark halos or floors. But these regions, like the rest of the Moon, have long been considered geologically dead. Circular maria are large, primordial impact basins that were filled with lava about 3 billion years ago. There is evidence, however, that volcanism has occurred in some craters that are perhaps only a million years old. Could the bright flashes, hazes, and colors reported at these sites be proof that the Moon is still active?
THOUGHTS ON THE ORIGIN OF LTP'S
Possible explanations for LTP's are not lacking. One of the earliest proposals was made by Jack Green of Douglas Advance Research Laboratories in Huntington Beach, California. While studying the standing levels of water and oil in deep wells, he found that the levels varied in concert with the Moon's anomalistic month (27.55 days, from perigee to perigee), as if the strength of the Moon's tidal force affected the tiny cracks in the bedrock through which oil and water move. Based on this idea, he suggested that LTP's are degassing phenomena brought about by the Earth's tidal effects on the Moon. Maximum degassing, he believed, would occur at the Moon's most eccentric apogees and a minimum at the least eccentric perigees. After analyzing 1,200 observations, however, I could not find such a relationship.
Some LTP phenomena may be caused by sunlight interacting with the lunar soil. On October 30, 1963, James Greenacre and Edward Barr observed red spots sparkling on the southwest wall of the crater Aristarchus, the east wall of Schroter's Valley, and a hill between them (S&T: December, 1963, page 316). The phenomena was observed visually by others and recorded spectroscopically as well. At the same lunar phase a month later, Greenacre and Barr saw a similar event. Since sunrise on these features occurs when the Moon is about 11 days old, Greenacre thought that the low lunar Sun was somehow responsible. Indeed, thermoluminesence may be the cause. Gases in the lunar soil, frozen during the night, could heat up and escape near sunrise.
Could high-energy solar particles impacting the Moon also trigger LTP activity? Shortly after a large flare erupted on the Sun in 1963, Zdenek Kopal and Thomas Rackham at Pic du Midi Observatory in southern France photographed a local brightening around the craters Copernicus, Kepler, and Aristarchus. Kopal proposed that energetic particles from the flare caused lunar rocks to fluorescence. Such activity might be expected especially at full phase when the Moon passes through the Earth's magnetosphere, where solar wind particles become trapped.
ANALYSIS
LTP sightings fall into five categories: brightenings darkenings, reddish colorations, bluish colorations, and obscurations. When plotted against the lunar anomalistic month, the data show that LTP activity peaks somewhat when the Moon is moving from apogee to perigee, especially about halfway between these points when the Moon is approaching Earth the most rapidly.
When the Moon is opposite that point in its orbit, LTP activity is at a deep minimum. Since tidal stressed build from lunar apogee to perigee, one might expect such a pattern.
When LTP phenomena are plotted against the Moon's phases, it appears that the most phenomena occur around the time of full Moon (though LTP's have been observed throughout the lunar cycle). Also, more are seen near the sunrise line than the sunset line, though that might be simply because far more people observe the waxing Moon in the evening than the waning Moon after midnight. Gaseous phenomena and anomalistic brightenings seem to peak when the Moon is a waxing crescent.
ARE THEY REAL?
Some astronomers dismiss all LTP's as either aberrational effects in Earth's atmosphere, changes in lunar lighting conditions, or outright illusions. Such skepticism, however, flies in the face of those who have devoted decades to familiarizing themselves with the Moon, and who very well know these common observational effects. LTP's are localized phenomena. They are regions or features that experience change while the rest of the Moon remains normal.
No doubt some apparent LTP's are caused by atmospheric effects. One is the "ashen glow." Here, sunlight scattered by Earth's clouds is cast onto the Moon's night surface, resulting in LTP's that simply reflect changes in the level of illumination. Another pseudo-LTP concerns bright features fringed with blue (north) and red (south) seen against dark backgrounds. These probably are aberrational effects, namely atmospheric dispersion near the observer, perhaps enhanced by a lingering temperature inversion.
Sightings of a starlike point on the Moon may also be disregarded as an LTP. This is the only transient phenomenon I have ever observed myself. But I suspect it is merely a reflection effect from flat facets on areas of large rocky outcrops when the Sun and observer are at just the correct angles. (High magnifications spread the light into an area instead of a point.)
Even if we eliminate the three types of non-LTP's discussed here, that still leaves more than 40 percent of the reports unexplained.
There is evidence that the remaining LTP's are of lunar origin. A substantial number of sightings were independently confirmed. Professional astronomers have recorded them on film and spectrograms, as well as with photoelectric photometers and polarization equipment. Experiments on the Apollo missions detected trace outgassings of the radioactive elements radon and polonium, suggesting that more substantial amounts of commoner substances were released at the same time. One experiment possibly detected water vapor during the largest moonquake on record (Richter 4).
The epicenter of that quake was near or in the large, fractured crater Gauss north of Mare Crisium.
While in lunar orbit, Harrison Schmitt of Apollo 17 witnessed a flash near the crater Grimaldi west of Oceanus Procellarum. Since he was dark adapted, it's possible he saw a cosmic-ray flash within his own eyeball. But it's also possible he saw a lunar event. In the past, Grimaldi had been responsible for more than a dozen reports of flashes. The crater Plato near Mare Imbrium is another source of flashes. Although many craters responsible for LTP sightings have central peaks with summit craters, Plato has none.
So the Moon may not be such a cold, lifeless neighbor after all. It still breathes through the action of LTP's, which in my opinion are probably gentle outgassings of less-than-volcanic proportions. Whatever they are, thanks to the LTP's, the Moon remains a curious place.
