Geological mapping of an interesting lunar site: Tsiolkovskiy crater

Tsiolkovskiy is a 180 km diameter late Imbrian crater located at 20.4° S, 129.1° E on the far side of the Moon [Whitford-Stark & Hawke, 1982].

Compared to the extensive mare deposits present of the lunar side facing the Earth, Tsiolkovskiy crater represents one of the few basaltic exposures on the far side [Pieters & Tompkins, 1999]. Along with its particularly dark and smooth crater floor, the impact crater is also characterized by a morphologically well-shaped central peak on which has been detected both olivine [Corley et al., 2018] and PAN [Ohtake et al., 2009; Lemelin et al., 2015].

The area represents thus a potential scientific site of interest for a safe landing. The production of geological maps aiming at characterize Tsiolkovskiy crater will allow the definition of interesting locations for rover exploration.

A geomorphological mapping of the crater has been performed using the ~100m/pixel LRO-WAC [Robinson et al., 2010] global mosaic along with the ~59m/pixel LRO-LOLA and Kaguya TC DEM merge which has a vertical resolution of 3-4m [Barker et al., 2016]. The mapping defined six units corresponding to the well-recognizable central peak and the texturally different smooth and hummocky materials constituting the crater floor units, and by scarps with slopes >40°, isolated ponds of smooth material discernible from the rough material constituting the crater rim and constituting the crater walls units.

The geomorphological mapping has then been coupled with a spectral characterization of Tsiolkovskiy crater performed on the basis of the ~200m/pixel Clementine UVVIS false color composite (Red 750/415nm; Green 750/1000nm; Blue 415/740nm) [Lucey et al., 2000]. The spectral mapping allowed to discriminate different units characterized by different origin and composition. In particular, the morphologically smooth crater floor unit is composed by fresher basalts and basaltic soils, the steep scarps and the central peak units are mostly composed by norites, troctolites and anorthosites, while the remaining smooth ponds, crater rim and the hummocky crater floor units are generally composed by mature highland soils.

In order to define landing ellipses and broad traverses for a rover exploration of the site, the geological mapping is also been supported by an ongoing high-resolution mapping of a quarter of Tsiolkovskiy crater by means of a mosaic of ~0.5m/pixel LRO-NAC [Robinson et al., 2010] images here scaled to 3m/pixel.

Finally, a radar investigation for the presence of deep structures will be performed to possibly detect lava pile emplacements and voids in the crater subsoil.

Acknowledgments

This research was supported by the European Union’s Horizon 2020 under grant agreement No 776276-PLANMAP.

References

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Pieters, C.M. & Tompkins, S., JGR, Vol. 104, pp. 21935-21949, 1999

Corley, L.M. et al., Icarus, Vol. 300, pp. 287-304, 2018

Ohtake, M. et al., Nature, Vol. 461, pp. 236-241, 2009

Lemelin, M. et al., JGR: Planets, Vol. 120, pp. 869-8878, 2015

Robinson, M.S. et al., Space Sci. Rev., Vol. 150, pp. 81–124, 2010

Barker, M.K., et al., Icarus, Vol. 273, pp. 346-355, 2016

Lucey, P.G. et al., JGR, Vol. 105, pp. 20377-20386, 2000