Friday, June 18, 2010

LROC: Test Wide Angle Camera Release

The Orientale basin is the youngest of the large lunar basins. The distinct outer ring is about 950 km from east-to-west, the full width of the LROC WAC mosaic is 1350 km [NASA/GSFC/University of Arizona].

Mark Robinson
Principal Investigator

The LROC team is producing preliminary large area mosaics with Wide Angle Camera (WAC) images now that enough data has been collected to derive inflight calibration coefficients and determine photometric corrections. The mosaic above is from images collected by the WAC in monochrome mode. When the sun is low on the horizon, color and reflectance variations are muted, so instead of imaging in the typical seven-color mode, image data from only one filter is read out. This gives a beautiful look at topography and morphology; later, when the sun is higher in the sky, the area is re-imaged in color, and the surface features can be correlated to their color signatures. Because the mosaic is preliminary, it still has some areas that appear black where image data was not included.

The mosaic is of the multi-ring basin Orientale, the youngest of the large lunar basins. Orientale is only partially flooded by later eruptions of mare basalt, unlike basins like Imbrium, so its internal structure is still visible. This view into the interior can help us learn more about basin formation and the mechanics of how basins develop their concentric rings. Orientale is the site of two Constellation regions of interest; one was the subject of a past featured image, the other is located near Kopff crater inside the basin. Kopff has unusual fractures in its floor (see NAC detailed view below), and the impact crater may have been modified by later volcanic activity, making it an exciting place to visit. Astronauts would also be able to sample the Maunder formation, thought to consist primarily of rocks that were completely melted by the heat generated during the impact.

A NAC view inside one of the fractures on the floor of Kopff crater, a 41 km crater within the Orientale basin and near the Orientale 2 Constellation Region of Interest. Image M122794259RE, scene width is 670 m [NASA/GSFC/Arizona State University].

The approximate location of the NAC detail above, in the range of the M122794259RE frame (yellow), is indicated with the small white square inside Kopff crater. The crater is easily visible on the right side of the central basin of Mare Orientale in the WAC Featured Image [NASA/GSFC/Arizona State University].

While LROC NAC images give unprecedented detailed views of the surface, WAC mosaics provide a synoptic view of the catastrophic power of large impact events, like the one that formed the Orientale basin. Explore the full-resolution NAC image of Kopff, and the full-resolution WAC mosaic of Orientale!

From Lunar Pioneer 3

Standing on the floor of Kopff, a glance over the NAC frame toward the crater rim, ~20 km away.

There is much to see in this medium-close up of the Wide Angle Camera mosaic of Mare Orientale, from the vent of the Orientale pyroclastic formation at center bottom to the complex fracturing and inner rings of the southwestern edge of the impact basin's central floor. The release of LROC WAC mosaics have been highly anticipated, filling gaps in our baseline understanding of the Moon's surface [NASA/GSFC/Arizona State University].

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