Lunar High Alumina Basalts in Mare Imbrium
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsIn this study, the compositions of exposed rocks in Mare Imbrium were determined using Lunar Reconnaissance Orbiter (LRO) Diviner oxides and Lunar Prospector Gamma-Ray Spectrometer (LP-GRS) Thorium (Th) products. The exposed HA basalts were identified based on laboratory lithology classification criteria and Al2O3 abundance. The HA basalt units were mapped based on topographic data and their morphological geological characteristics were calculated. The results show that there are 8406 exposed HA basalt pixels and 17 original units formed by volcanic eruptions in Mare Imbrium.
General comments:
The structure of this paper is clear, and the objective of this research is obtaining lunar high alumina basalts in Mare Imbrium based on laboratory lithology classification criteria and Al2O3 abundance.
Questions:
1) The Question or innovations of this research in not addressed in last part of Introduction, more questions should be listed in this position in order to compare the innovation with published achievements.
2) The figures of this paper are abnormal. For example, in Figure 3, the content and name of this Figure is located in different pages, left a and right b should be added in order to show different research regions. How to understand the vertical profile in Figure 4, what meaning for R=2.5km and f=2.37km?
3) Is the result of this research Figure 7? why not whole Moon? Is the position of F1-F17 right? Please check this position.
Comments on the Quality of English LanguageMinor editing of English language required
Author Response
Responds letter
Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Lunar high alumina basalts in Mare Imbrium”. Thank you very much for your encouragement and suggestions. According to your suggestions, we have supplemented the innovation points and research problems in the introduction section, adjusted the figures and modified the names of the figures, and explained the meanings of all parameters. These changes have certainly improved the quality and readability of the article. In addition, your questions point the way for our future research. In response to your suggestions, I have made the following changes to the manuscript:
Responds to reviewer1’s comments:
Point 1: The Question or innovations of this research in not addressed in last part of Introduction, more questions should be listed in this position in order to compare the innovation with published achievements.
Response: Thank you very much for your questions and suggestions. According to your suggestions, we have modified the last part of the introduction and added the innovation points and research problems of this paper. The supplement is as follows:
According to the composition relationship of adjacent pixels, the interference of the mare-highland mixture is excluded and the HA basalt pixels are identified, their distribution and the map of HA basalt units formed by the early volcanic eruption of Mare Imbrium are provided. The morphological and geological characteristics of these units are calculated, the patterns and eruption characteristics of early aluminiferous volcanic activity on the moon are analyzed.
Point 2: The figures of this paper are abnormal. For example, in Figure 3, the content and name of this Figure is located in different pages, left a and right b should be added in order to show different research regions. How to understand the vertical profile in Figure 4, what meaning for R=2.5km and f=2.37km?
Response: Thank you very much for your questions and suggestions. Based on your suggestion, we have modified Figure 3 to ensure that the content and names in the figure are on the same page. We also added a label "a" to the left and a label "b" to the right of the figure, and we changed the name of this figure. In addition, we have added the introduction of vertical profile and parameters such as R and f to new paragraphs so that readers can better understand them. Moreover, the new figure name introduces the details of the parameters in the figure. The new name is as follows:
Simplified vertical profile of the impact crater. a,b on the crater wall represent the calculate pixels, c,d,e and g on the edge represent the calculate interference factors. f is the threshold established based on the value of the impact crater radius R.
Point 3: Is the result of this research Figure 7? why not whole Moon? Is the position of F1-F17 right? Please check this position.
Response: Thank you very much for your questions and suggestions. Here I would like to explain: in Figure 7, we present the map of HA basalt units formed by the early volcanic eruption of Mare Imbrium, as identified by the distribution pattern of high alumina basalts. In order to make the reader more clearly see the outline and distribution location of the 17 HA basalt units, we do not show them in the whole moon. Based on the locations of the HA basalt pixels we identified, we confirm the locations of F1-F17 as a result of this study. In addition, your suggestions have provided us with important implications. According to your suggestion, we will identify HA basalts in all Mare and Cryptomare and calculate their morphological geological characteristics in future research. At the same time, gravity and anti-gravity data are combined to explore the location and geological characteristics of HA basalts below the regolith and basalt layers. This mission will be challenging, but will also lead to major breakthroughs in the study of the history of lunar volcanism.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Comments and Suggestions for AuthorsAuthors use remote-sensing data to provide some geological classifications of the high alumina basalts in Mare Imbrium on the Moon. Despite authors provide justification of their study, I did not find heir findings too convincing or novel. Area coverage is not significant new finding, age classification more or less confirmed previous findings. Estimations of the burial depth and thickness are controversial as method applied is not explained. These parameters are generally estimated by solving inverse gravimetric problems. At present, I am not convinced that this is legitimate study.
A more detailed list of my concerns is given below:
1/ l.58-63: “ Based on the sample composition returned by Apollo14 and Luna16 missions, the 58 Kramer team used Clementine Ultraviolet-Visible-Infared (UV-VIS) FeO and TiO2 and Lunar Prospector Gamma Ray Spectrometer (LP-GRS) Th data, combined with composition constraints (12-18 wt % FeO, 1-5 wt % TiO2 and 0-4 ppm Th), achieved the remote sensing 61 identification of HA basalts in Mare Moscoviense, Nectaris, Fecunditatis and Northern Imbrium”
This statement needs rephrasing
2/ l.63: Explain in more detail what is “optical maturity parameter”
3/ l.66: “on the lunar surface that may exist HA basalts.” what do you mean?
4/ l.69: “inaccurate Al2O3 abundance ” what do you mean?
5/ l.93: “According to these pixels, the morphological and geological characteristics of Mare Imbrium HA basalts are calculated by using lunar topographic data, and the eruption patterns and distribution characteristics of early Imbrium HA basalts are provided.”
Please explain the principle of how the morphological and geological characteristics of Mare Imbrium HA basalts are calculated by using lunar topographic data already in introduction.
6/ l.112: “according to the calculation method of Greenhagen et al.[51].”
Add some details about this method.
7/ l.132 “maria” ?
8/ l.197-199: “Most of the HA basalt layers were buried by regolith and mare basalt layers, their vertical position can be estimated by observing the position of HA basalt on the crater wall. ”
Rephrase this statement.
9/ l.200: “ digital elevation model [67] and the digital topography model provided ..”
is there any difference between topographic and elevation models?
10/ l.207: “Where i and j represent ” do not start with where as new statement. Rather continue it as previous statement
11/ Fig. 4. In legend provide explanation what is parameter R and f, and explain locations marked by a,b,c,…..
12/ l.246: “Mare Imbrium has a total of 80700 exposed rock pixels,”
This is strange statement that there are exposed rock pixels. Exposed can be area.
13/ L244-259. Paragraph: Provide area and relative % area coverage of individual lithologies.
14/ l.304-308: “F2 has the largest burial depth and its volume is the smallest among 17 units. The five north-central units have large areas (>10000 km2 ) and volumes, except for F10, the four units have similar thicknesses but different volumes. F9 and F10 have similar volumes but different thicknesses.”
15/ How did you estimated the burial depth and thickness?
16/ l.389: write: “characteristics in vertical thickness and maximum, minimum burial depths”
17/ Why there are no concluding remarks in Conclusion section related to thickness and burial depths?
18/ How this study can contributed to the Geological Atlas of the Lunar Globe and the Map Quadrangles of the Geological Atlas of the Moon compiled by the Chinese Academy of Sciences' Institute of Geochemistry?
19/ The limitations of the study are not given.
Author Response
Responds letter
Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Lunar high alumina basalts in Mare Imbrium”. We have modified and checked the full paper according to each of your suggestions, which undoubtedly significantly improved the level of the article. In addition, your suggestions point the way for our future research. According to your suggestion, we have tried to use Bouguer gravity anomaly data to calculate the morphological geological characteristics of high alumina basalts before. However, the spatial resolution of the gravity image is too low (8 ppd), while the spatial resolution of our high-aluminum basalt rock pixel image is 128 ppd. In low-resolution images, the identification information of high-alumina basalts will disappear, resulting in the failure of their morphological and geological features calculation. In the later stage, we will resample all the data to 8 ppd, try to use the gravity data to calculate the morphological geological characteristics, and expand the research scope to all the Mare and Cryptomare. This task will be challenging, but it will also bring a major breakthrough in the study of the history of lunar volcanic activity. In response to your suggestions, here are all of the modified I have made to the manuscript:
Responds to reviewer2’s comments:
Point 1: 1/ l.58-63: “ Based on the sample composition returned by Apollo14 and Luna16 missions, the 58 Kramer team used Clementine Ultraviolet-Visible-Infared (UV-VIS) FeO and TiO2 and Lunar Prospector Gamma Ray Spectrometer (LP-GRS) Th data, combined with composition constraints (12-18 wt % FeO, 1-5 wt % TiO2 and 0-4 ppm Th), achieved the remote sensing 61 identification of HA basalts in Mare Moscoviense, Nectaris, Fecunditatis and Northern Imbrium”
This statement needs rephrasing.
Response: Thank you very much for your suggestions. According to your suggestions, we have corrected the original statement on line 58 of the article to:
According to the composition range of HA basalt samples (12-18 wt% FeO, 1-5 wt% TiO2 and 0-4 ppm Th), Kramer team used Clementine Ultraviolet-Visible (UV-VIS) FeO and TiO2 and LP-GRS Th data, FeO was used as a proxy for Al2O3, achieved the remote sensing identification of HA basalts in Mare Moscoviense, Nectaris, Fecunditatis and Northern Imbrium.
Point 2: 2/ l.63: Explain in more detail what is “optical maturity parameter”
Response: Thank you very much for your suggestions. According to your suggestions, we have added an explanation of the "optical maturity parameters" in line 62 of the article. The supplementary contents are as follows:
Their study used optical maturity parameter (OMAT[41]), the parameter is used to reflect the degree of influence of space weathering such as solar wind and galactic cosmic rays on the lunar regolith[42].
Point 3: 3/ l.66: “on the lunar surface that may exist HA basalts.” what do you mean?
Response: Thank you very much for your questions. According to your questions, we have corrected the original sentence in line 65 of the article. The corrected contents are as follows:
Their study concluded that most of the ancient HA basalts were buried by basin ejecta and basalt flow, and were excavated to the regolith by small impact as ejecta at different periods. They used small impact projectile analysis to identify 34 regions of interest (ROI) for possible have HA basalts on the lunar surface[11,12,29].
Point 4: 4/ l.69: “inaccurate Al2O3 abundance “what do you mean?
Response: Thank you very much for your question. According to your question, we have corrected the original sentence in line 71 of the article. The corrected contents are as follows:
The correlation between FeO and Al2O3 of HA basalt samples is low (R2=0.4923), the method of using FeO to replace Al2O3 may not reflect the accurate abundance of Al2O3 in some regions.
Point 5: 5/ l.93: “According to these pixels, the morphological and geological characteristics of Mare Imbrium HA basalts are calculated by using lunar topographic data, and the eruption patterns and distribution characteristics of early Imbrium HA basalts are provided.”
Please explain the principle of how the morphological and geological characteristics of Mare Imbrium HA basalts are calculated by using lunar topographic data already in introduction.
Response: Thank you very much for your suggestion. According to your suggestion, we supplement the calculation principle of the morphology and geological characteristics of Mare Imbrium HA basalt in line 212 of the method section.
Point 6: 6/ l.112: “according to the calculation method of Greenhagen et al.[51].”
Add some details about this method.
Response: Thank you very much for your suggestion. According to your suggestion, we add the following in line 107:
Their study estimated the location of Christiansen Feature by a three-point parabolic fit to the emissivity of three bands (7.55-8.05, 8.10-8.40, and 8.38-8.68) around 8μm, and equally distributed channels in each 8μm region between 60° N/S at low spatial resolution (32 ppd).
The contents added in line 111 are as follows:
Greenhagen et al.[52] used a polynomial fit across latitudes to smooth the CF values of the highlands and calculated the Normalize Equatorial Noon (NEN) CF image based on the offset of the smoothed values from the highlands, the coverage of image increased to 82.5%.
Point 7: 7/ l.132 “maria” ?
Response: Thank you very much for your key question. According to your question, we have changed the ' maria ' in the full text to ' mare '.
Point 8: 8/ l.197-199: “Most of the HA basalt layers were buried by regolith and mare basalt layers, their vertical position can be estimated by observin observing the position of HA basalt on the crater wall. ”
Rephrase this statement.
Response: Thank you very much for your suggestion. According to your suggestion, we have corrected the original sentence in line 200. The corrected content is as follows:
Basaltic flow events and spatial weathering caused most of the HA basalt layers formed by the original volcanic eruption to be buried by the regolith and basalt layers. Fortunately, the position of the HA basalts excavated by impact on the crater wall is able to reflect the position of original HA basalts layer in the vertical direction. Meanwhile, elevation data and boundaries of HA basalt units can be combined to calculate their morphological and geological characteristics.
Point 9: 9/ l.200: “ digital elevation model [67] and the digital topography model provided ..”
is there any difference between topographic and elevation models?
Response: Thank you very much for your valuable suggestions. According to your suggestions, the “topographic datasets” in line 205 of the original text have been modified to “lunar elevation datasets”. The “digital topography model” in line 207 has been modified to the “digital elevation model”.
Point 10: 10/ l.207: “Where i and j represent ” do not start with where as new statement. Rather continue it as previous statement
Response: Thank you very much for your suggestion. Your suggestion makes us realize the ambiguity and deficiency of the calculation method of the morphological and geological characteristics of high-alumina basalt. In order to explain our research method more clearly, we deleted the second half of the original paragraph and added the method of calculating the buried depth and thickness of the HA basalt layer in the new paragraph, line 212. In addition, according to your suggestion here, we directly explain the position information represented by i and j in the formula in the narration, and no longer start with “where” as a new statement.
Point 11: 11/ Fig. 4. In legend provide explanation what is parameter R and f, and explain locations marked by a,b,c,….
Response: Thank you very much for your suggestion. According to your suggestion, we have added the introduction of the parameters R and f in the name of the map, as follows:
a,b on the crater wall represent the calculate pixels, c,d,e and g on the edge represent the calculate interference factors. f is the threshold established based on the value of the impact crater radius R.
Point 12: 12/ l.246: “Mare Imbrium has a total of 80700 exposed rock pixels,”This is strange statement that there are exposed rock pixels. Exposed can be area.
Response: Thank you very much for this very important suggestion. According to your suggestion, we supplement the map of Mare Imbrium rock classification (Figure 5) and the description of the area of different types of rocks. According to your suggestion, we describe the changed content in line 259, the changed content is as follows:
In Mare Imbrium, a total of 80,700 rock pixels with abundance >0.5 wt% were excavated to the regolith surface, their total area is approximately 4,842 km2, covering approximately 0.5% of the Mare Imbrium area.
Point 13: 13/ L244-259. Paragraph: Provide area and relative % area coverage of individual lithologies.
Response: Thank you for your suggestion. This suggestion can show our results more clearly. It undoubtedly improves the quality of this article. According to your suggestion here, we added the area for different lithologies and their relative area percentage in line 261 of the first part of the results, and added Figure 5, which makes it easier for readers to see the distribution of lunar rock types. We add the following:
The classification of these rocks is shown in Figure 5. It can be seen that most of the Mare Basalt (MB) pixels are concentrated in northern Mare Imbrium, a few scattered in southern. They are distant from highlands and irregularly distributed, with a total area of approximately 1,563 km2, accounts 32.3% of the rock pixel area. KREEP Basalt pixels have the opposite distribution characteristics with MB, they are less in northern where MB accumulation, and more in the southern, with a total area of about 1,551 km2, accounting for 32.0% of the rock pixel area. The Magnesian suite (MS) and Alkali suite (AS) have similar distribution patterns, they are concentrated on the edge of the impact crater, covering areas of approximately 1,261 km2 and 467 km2, respectively.
Point 14/15: 14/ l.304-308: “F2 has the largest burial depth and its volume is the smallest among 17 units. The five north-central units have large areas (>10000 km2 ) and volumes, except for F10, the four units have similar thicknesses but different volumes. F9 and F10 have similar volumes but different thicknesses.”
15/How did you estimated the burial depth and thickness?
Response: Thank you very much for this valuable question. Your question can make us describe the calculation method of the morphological and geological characteristics of HA basalt more clearly. According to your problem, we introduce the method of calculating the morphological and geological characteristics of HA basalt in detail in line 212 of the method part, and supplement the calculation method of burial depth and thickness of 17 HA basalt units in Mare Imbrium. Here I want to response your question: In this paper, the burial depth of the high-alumina basalt layer is calculated by the location of the HA basalt on the pit wall. In the calculation process, we use the distance constraint to reduce the influence of interference pixels such as spatter on the opposite and distal sides of the pit wall. The details are as follows:
The burial depth of HA basalt pixel is equal to the maximum elevation of the adjacent 10 pixels minus the elevation of the pixel. The thickness is equal to the maximum burial depth of adjacent 10 pixels minus the burial depth of the pixel. The maximum and minimum burial depths of HA basalt unit are equal to the maximum and minimum burial depths of HA basalt pixels on the crater wall inside the unit, and the thickness of unit is equal to the average thickness of HA basalt layer inside the unit.
Point 16/17: 16/ l.389: write: “characteristics in vertical thickness and maximum, minimum burial depths”
17/ Why there are no concluding remarks in Conclusion section related to thickness and burial depths?
Response: Thank you very much for your suggestion. According to your suggestion, we modified the first half of the conclusion by adding two summaries about thickness and burial depth, and supplemented it on line 499 in the second half. The supplementary content is as follows:
(5) In northern central part of Mare Imbrium, four units except F10 have similar maximum thickness. F2, located in Sinus Iridum, has the largest burial depth and the smallest volume. (6) The thickness of the HA basalt layers in different units is inconsistent, the distribution is discontinuous. Three levels for the thickness of the 17 units, the eruption source region of each grade is different and their composition is different. They may have originated during different periods and from different eruption sources.
Point 18: 18/ How this study can contributed to the Geological Atlas of the Lunar Globe and the Map Quadrangles of the Geological Atlas of the Moon compiled by the Chinese Academy of Sciences' Institute of Geochemistry?
Response: Thank you very much for your question. Your question is very forward-looking. Our research has been involved in the editing of these two atlases, we use the method in this paper to interpret the geological morphology of the basalts in Mare Imbrium and estimate their morphological geological characteristics. At the same time, we have published four foreign articles and one Chinese article, which has contributed to the accumulation of project results. Although we mainly use thermal infrared data to complete the related work, not directly using CE-1 data, the relevant research results can verify the interpretation results of the two atlases. In addition, we will provide strong support in the editing process of higher spatial resolution geological maps in the future.
Point 19: 19/ The limitations of the study are not given.
Response: Thank you very much for this very valuable suggestion. According to your suggestion, we make a supplement in line 399. The limitations of this study are as follows:
Firstly, our remote sensing identification method for HA basalts is applied to rock pixels with abundance >0.5 wt%, the HA basalts pixels buried by regolith or basalt flows may cause our method to fail. Secondly, HA basalt units adjacent to highlands or with less excavated rocks may be considered as ecdemic ejecta, and they cannot be identified. Third, the proximal ejecta at the crater edge and the HA basalt that slipped to the bottom of the crater make the thickness calculation inaccurate in this study. In the future research, we will comprehensively consider the gravity and anti-gravity factor, explore the distribution patterns and morphological geological characteristics of the HA basalts beneath regolith, basalt layers and deeper layers, and extend the research scope to the whole mare and cryptomare.
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsAuthors addressed all my comments.
