Lunar impact basins: New data for the western limb and far side (Orientale and South Pole‐Aitken Basins) from the first Galileo flyby

Head, J. W.; Murchie, S. L.; Mustard, John F.; Pieters, C. M.; Neukum, G.; McEwen, A. S.; Greeley, R.; Nagel, Engelbert; Belton, M. J. S.

doi:10.1029/93je01278

Cited by 136 publications

(125 citation statements)

References 40 publications

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“…But spectral data of central peaks of craters inside SPA show ultramafic assemblage dominated by magnesium rich orthopyroxene, suggesting the presence impact melt sheet 9) . This is compatible with previous remote-sensing data 10,11) . Then, higher crustal density would result in larger crustal thickness.…”

Section: South Pole Aitken Basinsupporting

confidence: 76%

Structure of the South Pole-Aitken Basin from KAGUYA Selenodesy Data

Sasaki

Ishihara

Goossens

et al. 2012

AEROSPACE TECHNOLOGY JAPAN

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The South Pole-Aitken basin (SPA) is the largest (2500km in diameter), deepest and presumably oldest impact basin in the solar system. SPA was characterized by an ellipse with axes 2400 by 2050 km, but more precise topography and gravity data are necessary to discuss the structure of large basin like SPA. We use localized representation of gravity potential where Slepian functions were used to estimate the gravity field over certain areas of the Moon and a spherical cap area with a radius of 40 degree from the SPA center. The direction of an ellipse denoting the depression is found to be similar to the previous result. The region with the thinnest crust is offset southward from the center of SPA. We analyzed interior structure of small basins in and around SPA. We interpret that a positive gravity anomaly corresponds to a Moho uplift. Just around the rim of SPA, a distinct Moho uplift beneath Schrödinger corresponds to the presence of olivine and obscure circular structure Amundsen-Ganswindt has a significant Moho uplift, suggesting a buried impact structure.

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Section: South Pole Aitken Basinsupporting

confidence: 76%

Structure of the South Pole-Aitken Basin from KAGUYA Selenodesy Data

Sasaki

Ishihara

Goossens

et al. 2012

AEROSPACE TECHNOLOGY JAPAN

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“…Thus the farside provides a more uniform cm•vas on which to record yom•g bright-rayed craters. A major exception to this generalization is the floor of the iron-rich South Pole-Aitken basin [Head et al, 1993;Lucey et al, 1995a].…”

Section: Introductionmentioning

confidence: 99%

The Phanerozoic impact cratering rate: Evidence from the farside of the Moon

McEwen¹,

Moore²,

Shoemaker³

1997

J. Geophys. Res.

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Abstract. The relatively recent (< 1 b.y.) flux of asteroids and comets forming large craters on the Earth and Moon may be accurately recorded by craters with bright rays on the Moon's farside. Many previously unknown farside rayed craters are clearly distinguished in the low-phase-angle images returned by the Clementine spacecraft. Some large rayed craters on the lunar nearside are probably significantly older than 1 Ga; rays remain visible over the maria due to compositional contrasts long after soils have reached optical maturity. Most of the farside crust has a more homogeneous composition and only immature rays are visible. The size-frequency distribution of farside rayed craters is similar to that measured for Eratosthenian craters (up to 3.2 b.y.) at diameters larger than 15 km. The areal density of farside rayed craters matches that of a corrected tabulation of nearside Copernican craters. Hence the presence of bright rays due to immature soils around large craters provides a consistent time-stratigraphic basis for defining the base of the Copernican System. The density of large craters less than -3.2 b.y. old is -3.2 times higher than that of large farside rayed craters alone. This observation can be interpreted in two ways: (1) the average cratering rate has been constant over the past 3.2 b.y. and the base of the Copernican is -1 Ga, or (2) the cratering rate has increased in recent geologic time and the base of the Copernican is less than 1 Ga. We favor the latter interpretation because the rays of Copernicus (800-850 m.y. old) appear to be very close to optical maturity, suggesting that the average Copernican cratering rate was -3 5% higher than the average Eratosthenian rate. Other lines of evidence for an increase in the Phanerozoic (545 Ga) cratering rate are (1) the densities of small craters superimposed on Copernicus and Apollo landing sites, (2) the rates estimated from welldated terrestrial craters (_< 120 m.y.) and from present-day astronomical observations, and (3) the Proterozoic rate suggested by the crater record of Australia. The hypothesis most consistent with several key observations is that the cratering rate has increased by-2x during the past-300 m.y..

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“…Ancient lunar volcanic deposits, known as cryptomaria (Head and Wilson, 1992), have been identified beneath basin ejecta deposits (e.g., Spudis, 1979, 1983;Hawke and Spudis, 1980;Hawke and Bell, 1981;Bell and Hawke, 1984;Hawke et al, 1993Hawke et al, , 2002Hawke et al, , 2005Hawke et al, , 2013Head et al, 1993;Antonenko et al, 1995;Blewett et al, 1995;Mustard and Head, 1996;Antonenko, 1999;Giguere et al, 2003;Campbell and Hawke, 2005;Lawrence et al, 2008). The name assigned to these ancient volcanic deposits, cryptomaria, implies that these ancient volcanic deposits are mare basalts.…”

Section: Introductionmentioning

confidence: 99%