Comments on the Proofs of Paper 1573

Comments on the Proofs of Paper 1573

The institution for Xio is: Planetary Science Institute, China University of Geosciences (Wuhan), Wuhan, Hubei 430074, China

There is a new address for co-author Ostrach as follows: NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA.

Figure 1 is out of place. You have it after the Abstract and before the Introduction. It should be within the Introduction on page 3. The description of Fig. 1 is OK as you have revised it.

1. INTRODUCTION

The first time “size frequency distribution” occurs is in the second paragraph of the Introduction. You should leave it there and just put (SFDs) in parentheses behind it. The rest of the changes in that paragraph are OK.

The changes in the 3rd and 4th paragraphs are OK.

The correction in the 5th paragraph is WRONG! There are two “form”. “these were only presented only in the form of an abbreviated summary form in Strom et al. (2005).” Leave it the way it was. The other changes are OK.

The corrections in the 6th paragraph are OK.

2 THE RELATIVE SIZE-FREQUENCY DISTRIBUTION PLOT

The title of the section 2 should remain “The Relative Size-Frequency Distribution Plot”. The other revisions are OK.

3 CRATERING RECORD OF THE MOON AND TERRESTRIAL PLANETS

For Section 3 the title should read “Cratering Record of the Moon and Terrestrial Planets”.

The corrections for section 3.1.1 Earth are OK.

The corrections for section 3.1.2 Moon are OK.

In Section 3.1.3 Mercury the word “corelates” in paragraph 3, page 7 is misspelled. It should be “correlates”. Otherwise, the corrections are OK.

In Section 3.1.4 Venus the word “modify” in the second sentence should be used. “Restrict” is the wrong meaning. The rest of the corrections are OK.

The corrections for section 3.1.5 Mars are OK.

3.2 Population S-The Secondary Crater Problem

In the second sentence, “The size and spatial distribution of secondary craters (Population S) generally depend on the size of the primary impact crater, the impact velocity, and the gravity field from the planet or satellite gravity field (e.g. Xiao et al. 2014).”, the correction should read “gravity field of the” not “from the”.

The sentence “This supports the interpretation that the upturn seen at small diameters, D . 1 km, in the R plot of the Mars Young Plains craters in young plains on Mars (see Fig. 10)” in the 5th paragraph should remain as it is. The Mars Young Plains is the name of the curve in Fig. 10.

This sentence “On Mercury, the contamination of secondaries might be extremely severe because some craters form very circular and isolated secondaries, even on continuous secondaries that are associated with facies, probably due to the special properties of the target properties (Xiao et al. 2014).:?” should not be changed. The word “facies” is geologically correct.

3.3 Summary of the Cratering Record for the Inner Solar System Cratering

Record:? This title should not be changed. It should remain, “Summary of the Inner Solar System Cratering Record”.

The sentence “The Venus curve is a composite of the production population forthat produced

all craters and for only multiple craters only.:? should not be changed. The terms “production population” are correct. The other corrections are OK.

3.4 The Outer Planet Cratering Record

This sentence, “None of crater populations on satellites of the outer planets

satellites’ crater populations resemble the cratering record on the heavily cratered terrain of the

Moon andor the innerterrestrial planets.:? “ should read “None of the crater populations of on the outer planet satellites resemble the cratering record on the heavily cratered terrain of the Moon or terrestrial planets.”

4 DISCUSSION

4.1 Sources of Population 1 and Population 2 Impactors

The modification to the first sentence in the first paragraph is WRONG (The size of an impact crater is related to the size of a crater made by the impactor as defined by the Pi-group crater scaling law (Croft 1985; Schmidt & Housen 1987; Melosh 1989; Collins et al. 2005).:? The sentence should stay as it was. The size of a crater is related to the size of the impactor, not the “size of the crater made by the impactor”. The other changes to the first paragraph are OK.

The modifications to the second paragraph are OK.

The modifications to the third paragraph are OK.

In the fourth paragraph you have added two “have”s to one sentence. The other change is OK.

The modifications to the rest of section 4.1 are OK.

4.2 Age and Duration of the Late Heavy Bombardment

The modifications of section 4.2 are OK.

4.3 Dynamical Mechanism for LHB

The modifications of section 4.3 are OK.

4.4 Implications for Age Dating from the Impact Crater Record

The first sentence in the 1st paragraph should not be modified. The obliteration is indeed “significant”, not “to some degree”.

The last sentence in this section should not be changed.

5 SUMMARY

The last sentence in this section should not be changed.

The changes to Table A.1 are OK.

References

The Ostrach Icarus paper is now published. It is as follows:

Ostrach, L.R., M.S. Robinson, J.L. Whitten, C.I. Fassett, R.G. Strom, J.W. Head, and S.C. Solomon, 2015, Extent, age, and resurfacing history of the northern smooth plains on Mercury from MESSENGER observations, Icarus, 250, 602-622.

The other corrections to the references are OK.

Figure Captions and New Figure 13.

Figure 2. The last sentence should read: “The shaded area in the bottom panel shows the difference in the crater distribution from Population 1.”

Figure 13. The first sentence should read: “The impact crater SFDs on the heavily cratered (h. c.) units on Jupiter and Neptune satellites (a), and Saturn and Uranus satellites (b).” The other sentence is OK.

The changes in all other Figure captions are OK. Attached to this e-mail is the new Figure 13 with much higher definition.