Comparison of lunar red spots including the crater copernicus

• Y. Shkuratov^a,

• V. Kaydash^a,

• L. Rohacheva^a,

• V. Korokhin^a,

• M. Ivanov^{b, c},

• Y. Velikodsky^{a, d},

• G. Videen^{e, f}

• ^a Institute of Astronomy, Kharkiv V.N. Karazin National University, 35 Sumskaya St., Kharkiv 61022, Ukraine

• ^b V. I. Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, 19 Kosygin Str., Moscow 119991, Russia

• ^c Moscow State University of Geodesy and Cartography (MiiGAIK), 105064 Moscow, Gorokhovsky 4, Russia

• ^d National Aviation University, Cosmonaut Komarov Ave. 1, Kiev 03680, Ukraine

• ^e Space Science Institute, 4750 Walnut St. Suite 205, Boulder, CO 80301, USA

• ^f Army Research Laboratory AMSRL-CI-EM, 2800 Powder Mill Road, Adelphi, Maryland 20783, USA

Received 8 September 2015, Revised 11 February 2016, Accepted 23 February 2016, Available online 3 March 2016

Highlights

• The NW quadrant of the crater Copernicus reveals itself as a red spot on the Moon.

• This is similar to Hansteen Alpha and others extrusions of rhyolite composition.

• The Copernicus red spot is formed from a rhyolite extrusion by the impact.

• The red asymmetry of Copernicus ejecta can be related to the impact eccentricity.

Abstract

The lunar red spots, Helmet, Hansteen Alpha, and the NW quadrant of the crater Copernicus, were selected for a complex comparative investigation of their characteristics measured by the spacecraft Clementine, LRO, and Chandrayaan-1. For the analysis we used the following parameters: the reflectance A(750 nm), color-ratio A(750 nm)/A(415 nm), parameter of optical micro-roughness (LRO WAC), parameters deduced from LRO Diviner data, optical maturity OMAT, abundance of FeO and TiO₂ (Clementine UVVIS and LRO WAC data), oxygen content determined using Lunar Prospector data, and parameters characterizing the 0.95-µm and 2.2-µm bands of Fe²⁺ ions (crystal field bands), and 2.8-µm band of H₂O/OH and/or Fe²⁺ ions. The red spots Helmet and Hansteen Alpha are considered to be extrusions of rhyolite composition, which can be attributed to the Nectarian period; we did not find contradictions of this assumption. As for the Copernicus red spot, this, perhaps, is a similar formation that has been destroyed by the impact. We demonstrate that the material of the Copernicus red spot probably has the same composition as the classical red spots Helmet and Hansteen Alpha. The distributions of the parameter of optical micro-roughness and optical maturity OMAT show that the Copernicus red anomaly was not formed during the long evolution of the lunar surface, but results from crater formation. We find several confirmations of the hypothesis that the Copernicus red spot can be a residual of a red material (possibly rhyolite) extrusion that was involved in the impact process. The red material could have been partially melted, crushed, and ejected to the crater's north-western vicinity. The described red asymmetry of the Copernicus ejecta can be related to the eccentricity, relative to the extrusion, of the impact and/or to the inclination of the impactor trajectory. The latter also is confirmed by an analysis of the region, which is based on the geological map shown in this paper.

Keywords

• Moon, Surface;

• Photometry;

• Spectrophotometry

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