The document discusses the Curiosity Clock app, which allows users to view the time and sky as seen from the Curiosity rover on Mars. Key points: 1) The app uses data from the Curiosity rover mission to calculate Martian solar time and the sun's position to simulate the Martian day/night cycle, sky color, shadows, and sunrise/sunset times. 2) Terrain data of Gale Crater from the MOLA instrument allows rendering of a 3D terrain model while orbiter images provide texture details. 3) In addition to the day/night sky effects, the app includes views of stars as they would appear from Mars' surface at night