Thursday, December 3, 2009

LRO's Mini-RF Serenitatus Swath

LRO Mini-RF S-band zoom synthetic aperture radar (SAR) image strip through central Mare Serenitatis on the near side of the Moon (approximate longitude of strip ~ 18° E; center latitude ~ 20° N). (Full Image HERE.)

The radar strip runs through the crater Bessel (inset; 17 km (10 mile) diameter; center at 21.8° N, 17.9° E) and covers the highlands of the Haemus Mts. (rim of Serenitatis basin) in its southern (bottom) third. The full-resolution SAR data are 30 m (90 feet). The streaks of bright and dark material in the walls of Bessel probably reflect the blockiness of landslides within the crater, brighter streaks having more blocks of the 10-cm (4-inch) scale. The radar strip covers a major geological boundary in Mare Serenitatis; the darker, lower maria has higher titanium content than central Serenitatis. We see this geological boundary in the Mini-RF radar image, caused by higher absorption of RF energy by the high content of the iron-titanium oxide mineral ilmenite. Thus, Mini-RF SAR images can be used to map the titanium content of the lunar maria. The background image is part of the Clementine global mosaic [NASA/GSFC].

For no particular reason, a notional view of the interior of Bessel as seen within the Apollo corridor, the high-definition digital elevation model supported in all current versions of the Moon as seen in Google Earth application. Bessel stands out in minimal telescopes from Earth. It's easy to spot, just south of the basin's center, though there is some question whether the 17 km crater actually lies inside a prominent ray of Tycho, running north from Menelaus. That ray does seem to originate at Tycho, though it is slightly "off" when traced all the way back to the more famous ~109 year old crater 2100 km away in the southern highlands. But this "discontinuity" may just be a matter of perspective, an optical illusion, since the ray lines up well with Tycho when viewed from directly overhead.

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