УДК 523 Солнечная система
УДК 53 Физика
УДК 520 Инструменты, приборы и методы астрономических наблюдений, измерений и анализа
УДК 521 Теоретическая астрономия. Небесная механика. Фундаментальная астрономия. Теория динамической и позиционной астрономии
УДК 524 Звезды и звездные системы. Вселенная Солнце и Солнечная система
УДК 52-1 Метод изучения
УДК 52-6 Излучение и связанные с ним процессы
ГРНТИ 41.19 Солнечная система
ГРНТИ 41.00 АСТРОНОМИЯ
ГРНТИ 29.35 Радиофизика. Физические основы электроники
ГРНТИ 29.31 Оптика
ГРНТИ 29.33 Лазерная физика
ГРНТИ 29.27 Физика плазмы
ГРНТИ 29.05 Физика элементарных частиц. Теория полей. Физика высоких энергий
ОКСО 03.06.01 Физика и астрономия
ОКСО 03.05.01 Астрономия
ОКСО 03.04.03 Радиофизика
ББК 2 ЕСТЕСТВЕННЫЕ НАУКИ
ББК 223 Физика
ТБК 614 Астрономия
ТБК 6135 Оптика
BISAC SCI004000 Astronomy
BISAC SCI005000 Physics / Astrophysics
We study the morphometric parameters of 111 lunar craters with a diameter of 10 km or more, the formation of which, according to some researchers, can be attributed to the Copernican period. These craters were selected by analyzing data from the Diviner spectrometer on board the LRO probe. The purpose of this work is to study the morphometric characteristics of such craters in order to identify their characteristic features. According to the results obtained, the morphometric parameters of the fresh lunar craters are significantly similar to the morphometric parameters of lunar craters of the 1st degree of degradation (well-preserved craters) according to the classification of the SAI MSU.
Moon; craters
Morphometric parameters of fresh lunar craters
E. Feoktistova1, Zh. Rodionova1, and V. Shevchenko1
Sternberg State Astronomical Institute, Lomonosov Moscow State University, Moscow, 119234, Russia
Abstract. We study the morphometric parameters of 111 lunar craters with a diameter of 10 km or more, the formation of which, according to some researchers Mazrouei et al. (2019), can be attributed to the Coper- nican period. These craters were selected in Mazrouei et al. (2019) by analyzing data from the Diviner spectrometer on board the LRO probe (https://www.diviner.ucla.edu). The purpose of this work is to study the morphometric characteristics of such craters in order to identify their char- acteristic features. According to the results obtained, the morphometric parameters of the lunar craters from the (Mazrouei et al., 2019) are signif- icantly similar to the morphometric parameters of lunar craters of the 1st degree of degradation (well-preserved craters) according to the classifica- tion of the SAI MSU.
1 Introduction
Impact craters have appeared on the lunar surface throughout its his- tory, which is 4.6 billion years. The youngest lunar craters were formed during the Copernican period, which began 1.1 billion years ago and continues to the present time. The shape of an impact crater is determined by the parameters of the collision that formed it and the age of the crater. Quantitative characteristics of the crater shape are its morphometric parameters. The main morphometric parameters of impact craters, following Slodarz (2021), are their diameters, the inclination angles of the external and inner slopes, the maximum and minimum depths and the height of the crater bottom. Analysis of data obtained by the Diviner infrared spectrometer on the LRO probe showed that 111 lunar craters are clearly visible in the IR range: the ejecta of these craters heated and cooled more slowly than the surrounding surface. The authors of the work Mazrouei et al. (2019) attribute this to the fact that these craters were formed over the last billion years and their ejecta have not yet been fragmented by the fall of other bodies and contain a significant number of large fragments. We compared the morphometric parameters of such craters with the morphometric parameters of well-preserved lunar craters.
2 Comparison of morphometric parameters of craters
According to the classification of craters by the degree of degradation of the SAI MSU, impact craters can be divided into 5 degradation classes: class 1 includes well-preserved craters that have a pronounced clear rim and often a system of rays, crater-ruins belong to the 5th degradation class. Degradation class 1 craters make up 19 % (2850) of the total number of lunar craters with diameter 10 km or more. The degree of degradation of a crater does not always depend on its age: for example, the Sharonov crater (12.4◦ N, 173.3◦ E), which belongs to 1st degradation class, was formed in the Eratosthenes period of lunar history (3.2 - 1.1 billion years ago). In this paper, we attempted to determine the morphometric features of fresh craters that would allow us to distinguish them from well-preserved craters of different ages. In the Morphological Catalog of Craters of the Moon Rodionova et al. (1987), craters related to the 1st degradation class were selected. To determine the morphometric parameters of the craters, data from the LOLA altimeter of the LRO probe were used (https://ode.rsl.wustl.edu/moon/). Altitude profiles of 111 fresh craters Mazrouei et al. (2019) and 150 craters of the 1st degradation class were studied (Fig.1). The distribution of craters by diameter for both crater groups is similar: the diameters of most craters in both groups (92 % of craters Mazrouei et al. (2019) and 96 % of craters of the 1st degradation class according to the classification of the SAI MSU) lie in the range of 10–30 km with a maximum in the range of 10–20 km. As can be seen from figure 2, height of the crater rim for both groups lies in the range of 200 – 2000 m. About 60 % of the craters of the 1st degradation class and 81 % of fresh craters Mazrouei et al., (2019) have a rim height of 400 - 800 m. The values of the inclination angles of the inner slopes of the craters for both groups of craters are approximately the same, ranging from 10 to 40 degrees. For the majority of craters of degradation class 1 according to the SAI MSU (73 %), the inclination angles of the inner walls of the crater lie within the range of 20 – 25 degrees. Most of the craters from Mazrouei et al. (2019) have steeper innerslopes: the inner slope angles of such craters are in the range of 25–35 degrees. Most craters of degradation class 1 according to the SAI MSU classification (86 %) have inclination angles of external walls within the range of 2–8 degrees. The outer rims of the craters from Mazrouei et al. (2019) are on average slightly steeper: the inclination angles of the outer walls of the majority (85 %) of these craters are in the range of 4 – 12 degrees. The depth distribution of craters of both groups shows similarities. The depths of most of the craters of the 1st class of degradation according to the SAI MSU (71 %) lie within the range of 1800 - 3200 m (Fig. 3). The depths of the majority (86 %) of fresh craters from Mazrouei et al. (2019) lie approximately within the same range (1600 - 3200 m).
3 Conclusions
The morphometric parameters of lunar craters Mazrouei et al. (2019) are largely sim- ilar to the morphometric parameters of lunar craters of the 1st degree of degradation according to the SAI MSU. At the same time, the craters from Mazrouei et al. (2019) have slightly steeper inner and external slopes. Thus, no significant differences were found in the morphometry of craters determined by thermophysical properties as fresh from the morphometry of well-preserved lunar craters according to the SAI MSU data.
1. Slodarzh N., 2021, Vupusknaya kvalifikatsionnaya rabota bakalavra, p. 271
2. Mazrouei S., Ghent R., Bottke W., et al., 2019, Science, 363, 6424, p. 253
3. Rodionova Zh.F., Karlov A.A., Skobeleva T.P., et al., 1987, Morphological Catalogue of the Craters of the Moon, Moscow University Press
