Daily Extra :
Have you ever heard a sonic boom? When an airplane travels at a speed faster than sound, density waves of sound emitted by the plane accumulate in a cone behind the plane. When this shock wave passes, a listener hears a sonic boom. Large meteors and the Space Shuttle frequently produce audible sonic booms before they are slowed to below the sound of speed by the Earth's atmosphere.
Who Was Born Today?:
1947: Sergey Filipovich Protchenko, Russian cosmonaut
Who Died Today?:
Today in History:
1963: Mariner 2 - USA Venus Flyby (August 27, 1962 - January 3, 1963) went off the air. On December 14, 1962, Mariner 2 arrived at Venus at a distance of 34,800 kilometers and scanned its surface with infrared and microwave radiometers, capturing data that showed Venus's surface to be about 425°C (800°F). Three weeks after the Venus flyby Mariner 2 went off the air on January 3, 1963. It is now in a solar orbit.
1999: Launch of Mars Polar Lander and Deep Space 2 probes. The Mars Polar Lander, also known as the Mars Surveyor '98 Lander, was a companion to the Mars Climate Orbiter. It was to touch down on the southern polar layered terrain, between 73 S and 76 S, less than 1000 km from the south pole, near the edge of the carbon dioxide ice cap in Mars' late southern spring. The last telemetry from the spacecraft was sent just prior to atmospheric entry on 3 December 1999. No further signals have been received from the lander, the cause of this loss of communication is not known.
The Deep Space 2 (DS2) project is a New Millenium mission consisting of two probes which were to penetrate the surface of Mars near the south polar layered terrain and send back data on the sub-surface properties. On 3 December 1999 the probes were nearing Mars on a trajectory to enter the atmosphere and bring them to their intended landing site, but contact was never made with either probe and the mission was presumed lost.