ORIGIN AND NATURE OF THE MOON — UREY 263 



craters have no rays: possibly they are older and the rays have be- 

 come obliterated by the fall of niicrometeorites, or perhaps, again, 

 the moon had a temporary atmosphere when they were formed. Pro- 

 clus has rays extending in all directions except towaixl the southeast : 

 Fielder has reported tlie presence of a ridge tliere which may have 

 intercepted the particles. If this is the correct interpretation, we can 

 conclude that the collision sprayed out this material in a horizontal 

 direction. Chemical effects sucli as the escape of gases from below 

 the surface may also have been important in producing this unsym- 

 metrical ray pattern. 



N. Kozyrev [8] has reported that, during November 1958, gases 

 escaped from the region of the central peak of Alphonsus, and he pub- 

 lished a spectrum of these gases. He states that the original spectrum 

 shows the presence of the Co bands which are prominent features of 

 comet spectra. No change in the appearance of the central peak has 

 been noted, and thus this could not have been a typical volcanic erup- 

 tion such as is observed on the earth; possibly it was an eruption of 

 water from the interior. Many small black areas have been observed 

 in various parts of the moon, and in fact several examples appear in 

 Alphonsus. Often they have small craters in their centers and look 

 as though gaseous eruptions of some kind had occurred. If C2 — or 

 rather, compounds which the solar light dissociates to give C2 — escapes 

 from the moon, some blackening of the surface by graphite should 

 occur. 



A very curious and puzzling feature of the surfaces of the m.aria are 

 the great sinuous wrinkles some 100 meters high, some kilometers wide, 

 and hundreds of kilometers long. G. P. Kuiper [9] has recently re- 

 ported that there are often cracks along their tops, and in some cases 

 white material can be seen in these cracks. Does the white material 

 consist of encrustations of salt, possibly deposited by escaping Avater? 

 J. W. Salisbury [10] has made an interesting suggestion in regard to 

 some rounded hills that have been observed for many years. He sug- 

 gests that water has caused hydration of olivine present in these re- 

 gions, causing it to swell and elevate the surface. Possibly the wrin- 

 kles in the maria overlay cracks below, through which water rises 

 from the interior. The wrinkles look much like sand dunes or slides 

 of some Idnd. Their origin is uncertain, but probably tliey are super- 

 ficial in origin, and the unraveling of the puzzle will contribute little 

 toward a fundamental understanding of the moon. 



Long cracks occur in various regions of the moon, and in some places 

 craters are distributed along them. The curious distribution of the 

 craters along these cracks shoAvs that they are certainly not due to col- 

 lisions. They are due to the escape of gases from the interior, and have 

 long been interpreted in this way. An outstanding example lies just 



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