... To help find out, NASA launched the twin Gravity Recovery and Interior Laboratory (GRAIL) satellites in 2011 to orbit and map the Moon's surface gravity in unprecedented detail. Comet PANSTARRS Just After Sunset . ... After appearing in a popular photo opportunity with a young crescent Moon near sunset, naked-eye Comet PanSTARRS continues to rise in northern hemisphere skies. ... The comet stands over the western horizon after sunset, joined by the thin, flattened crescent of a day old Moon. ...