Copernicus Crater Research Articles

Laboratory simulation of the herringbone pattern associated with lunar secondary crater chains

V-shaped ridge components of the herringbone pattern associated with lunar secondary crater chains have been simulated by simultaneous and nearly simultaneous impact of two projectiles near one another. The impact velocities and angles of the projectiles were similar to those of the fragments that produced secondary craters found at various ranges from large lunar craters. Variables found to affect the included angles of the V-shaped ridges are: relative time of impact of the projectiles, impact angle, relative projectile mass, and azimuth angle of the crater chain relative to the projection of the flight line onto the target surface. The functional relationships between the forms of the ridges and many of these variables are similar to those observed for lunar V-shaped ridges. Comparison of the magnitudes of the ridge angles of both laboratory crater pairs and secondary crater chains of the crater Copernicus implies that material was ejected from Copernicus at angles in excess of 60°, measured from the normal, to form many of Copernicus' satellitic craters. Moreover, other independent calculations presented indicate that many of the fragments that produced secondary craters also ricocheted to produce tertiary craters. Application of the study to identification of isolated secondary craters and to the determination of the origin of large lunar craters is discussed.

Lunar crater Copernicus: search for debris of impacting body at Apollo 12 site

In an attempt to characterize meteoritic material at the Apollo 12 site, 4 KREEP concentrates from soil 12033 have been analyzed by neutron activation analysis. These contain a meteoritic component in which siderophile Ir, Re and Sb are depleted by about a factor of 2, while volatile Se, Zn, Ag and Bi are depleted by a factor of more than 5 relative to Au. This pattern does not closely resemble any major chondrite or iron meteorite group, but is very similar to that observed in high-alkali samples from Apollo 14. The meteoritic component in KREEP at both sites is therefore predominantly derived from Imbrian ejecta. However, a second, small component of primitive composition seems to be present in Apollo 12 KREEP, judging from the slight, uniform enrichments in Ir, Re, Sb, Se and Zn relative to Au. This component does not seem to be due to micrometeorites. If it is attributed to the Copernican projectile, the crater Copernicus may have been formed by a cometary nucleus, 4 km in diameter, with an impact velocity of 30–40 km/sec. These conclusions depend critically on the assumption that the meteoritic component in Apollo 12 KREEP is representative of the entire impact.

How old is the crater copernicus?

Two KREEP glass concentrates separated from lunar soil 12033 have been dated with the Ar39/Ar40 method. Both samples show low-temperature plateaus in accordance with a major outgassing of the KREEP glasses (800 ± 40) × 106 yr ago. This is the age of Copernicus, provided the identification of KREEP glass as ray material ejected during the Copernican event is true (Hubbardet al., 1971). The exposure age of the two KREEP glass concentrates is 200 × 106 yr and thus distinctly smaller than the ejection age. Possible explanations for this are discussed.

Copernicus as a Lunar Caldera

All morphological features observed in and around the crater Copernicus are in agreement with a simple volcanic origin. The crater appears to be a caldera exhibiting the following features: multiple volcanoes on the crater floor, lava-floored terraces of different ages, interior leveed lava-flow channels, interior nested domes, near-horizontal lava or ash flows on the walls, exterior lava and tuff flows, and arcuate arrays of elongate volcanic craters on the caldera flanks. The orientation of caldera wall segments, volcano and dome alignments on the floor, and elongate (explosion or fluidized?) craters and craterlets on the flanks is parallel with major tectonic patterns in the Copernicus area. Copernicus is polygenetic. Impact-triggered volcanism is thought to be unlikely in this and other large lunar or terrestrial craters.

Endogenetic Craters Interpreted from Crater Counts on the Inner Wall of Copernicus

Collapse craters formed in terrestrial basalt flows exhibit size-frequency distributions that are similar to distributions for craters located in terraces in the inner wall of the lunar crater Copernicus. These distributions and surface morphology suggest that the interior terraces are basalt lava flows containing collapse craters as well as impact craters.

A mechanism for the production of lunar crater rays

Observations of high resolution photographs of part of one of the prominent rays of the lunar crater Copernicus show that there is a concentration of small bright rayed and haloed craters within the ray. These craters contribute to the overall ray brightness; they have been measured and their surface distribution has been mapped. Sixty-two percent of the bright craters can be identified from study of high resolution photographs as concentric impact craters. These craters contain in their ejecta blankets, rocks from the lunar substrate that are brighter than the adjacent mare surface. It is concluded that the brightness of the large ray from the crater Copernicus is due to the composite effect of many small concentric impact craters with rocky ejecta blankets. If this is the dominant mechanism for the production of other rays from Copernicus and other large lunar craters, then rays may not contain significant amounts of ejecta from the central crater or from large secondary craters. They may in fact only reflect local excavation of mare substrate material by myriads of small secondary or tertiary impact craters.

Infrared emissivity of lunar surface features: 2. Interpretation

Thermal emission spectra of six different areas on the lunar surface are discussed in the light of laboratory studies of the spectral emissivity of rocks and minerals. It is shown that the emission maxima characteristics of lunar spectra are similar to emission maxima found in the spectra of particulate rock samples. Such emission maxima are shown to be diagnostic of general rock type, within limits that are defined. Differences in emission maxima of their respective spectra indicate a significant difference in bulk composition between the material ejected by the craters Copernicus and Theophilus and the surface material of the two circular maria, Imbrium and Serenitatis. Barring some unknown measurement error in the spectra, or some unanticipated effect of the lunar environment on surface spectral behavior, we can conclude that the crater materials display an emissivity maximum characteristic of silica-poor basic rocks, while the circular maria display a maximum characteristic of silica-rich ultrabasic rocks. If this preliminary result is confirmed by future research, it has profound implications for the origin and evolution of the lunar crust.

Lunar Thermal Anomalies: Infrared Observations

The lunar craters Tycho, Copernicus, and Aristarchus have been observed during lunar night at wavelengths between 3 and 14 microns. After an initial fast decrease to a color temperature of 220 degrees K, the temperature remains nearly constant through the lunar night. The data suggest that these thermal anomalies (craters) contain hot and cold regions with the hot portions constituting 2 to 10 percent of the area and probably thermally connected to a subsurface temperatuer of about 200 degrees K.

Secondary craters

Secondary craters formed by the impact of ejecta missiles generally occur outside the lip crest of explosion-induced shock craters. Numerous shallow depressions occurring in the region adjacent to the lunar crater Copernicus have also been interpreted as secondary craters. Missiles which produce secondary craters are: 1. Comminuted and shock compacted material. 2. Single rock or soil fragments. 3. Fragments of structural material. 4. Unconsolidated but discrete masses of crater ejecta. Superposition of ejecta layers, exposed of excavation of the large secondary craters near Sedan, indicates that unwinnowed material arrives first followed by the large masses of unconsolidated alluvium. The impact of these masses forms secondary craters that are essentially compressional features. The large masses are followed winnowed ejecta separated by passage through the atmosphere into a coarse fraction deposited as individual grains and a fine fraction that is deposited relatively slowly as long as the dust cloud remains in the area. The secondary craters observed on Earth have all been formed by missile impact ve velocities lower than the acoustic velocity of the medium; however, on the Moon, primary as well as secondary impact craters can be produced at both subsonic and hypersonic velocities. This indicates that the use of shock crater frequency to infer flux of larger meteorites may not be valid.

Ray Elements and Secondary-Impact Craters on the Moon.

view Abstract Citations (9) References (7) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Ray Elements and Secondary-Impact Craters on the Moon. Fielder, Gilbert Abstract Fifty-nine lunar craters, mostly between 1 and S km in diameter, are identified with certain ray elements of the major ray craters Copernicus and Tycho. A catalogue of the positions of the small cratets is given, and it is demonstrated that they are "secondary-impact craters" produced by rock blocks ejected from Copernicus and Tycho It is shown that the elliptical shape of some of the secondary craters does not depend on the direction of impact of the rock blocks. The mechanics of the process of formation of the secondary craters and their ray elements is discussed for maria composed of (a) a dusty medium and (b) a medium such as solid rock. Publication: The Astrophysical Journal Pub Date: March 1962 DOI: 10.1086/147296 Bibcode: 1962ApJ...135..632F full text sources ADS |

Kinematographic Record of Sunrise on the Moon

ON the night of May 17–18, 1929, between 1.5 h. and about 5.5 h. Greenwich civil time (18 d.) a moving picture was made here of the lunar crater Copernicus, showing changes in the shadows at sunrise. A Victor kinema camera, using amateur-size film (16 mm.), was employed, attached in the focal plane of the 23-inch refractor (30 feet focal length) of the Princeton University Observatory. A yellow Wratten filter No. 45 was inserted about 15 inches ahead of the film. Exposures were made every 6 seconds, approximately, for about 4 hours, on Agfa negative film. The duration of each exposure was about 3.8 seconds, controlled by the rotating camera shutter (sector opening 200°), which was driven by a belt from a light electric motor carried in the same aluminium frame.