April 13, 2011

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Refined Ages

LPOD-Apr13-11.jpg
Kaguya Terrain Camera image (a) and derived mare ages (d) from Tomokatsu Morota and colleagues (2011)

The ages of lunar lava flows are important because these surface rocks provide evidence about the thermal evolution of the lunar interior. Based on radiometric dating of returned samples, lunar volcanism occurred between about 4.3 and 2.5 billion years. But Apollo and Luna samples come from only 10 locations so there are many places that remain un sampled and undated. As we have seen before counting the number of impact craters has become an effective proxy for radiometric dating so that we can count craters and infer model ages for all the maria. Japanese scientists have now refined crater counting using 10 m resolution images from the Terrain Camera on the Kaguya spacecraft. There crater counts were within the north western part of the Moon where prior work indicated the youngest lunar maria lavas were located. The new results confirm that lavas erupted in a ribbon (orange) west of Kepler and also east of Bessarion. These lavas are 1.5 to 1.6 billion year old - the youngest on the Moon - so it would be expected that their vents would be easily detected, but I don't see them in a quick search. Also, notice the patch of yellow in the middle of Mare Imbrium. This 1.8 b.y. old lava flow is surrounded by lavas about 3 b.y. old; I wonder if the vent for these yellow flows was along one of Imbrium inner basin rings?
Chuck Wood

Related Links
Timing and characteristics of the latest mare eruption on the Moon. T. Morota and colleagues (2011). Earth and Planetary Science Letters, Volume 302, Issue 3-4, p. 255-266.


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