Daily Extra :
Astronomy & Space Word of The Day
orbital period: The time required for an object to make a complete revolution along its orbit.
Today in History:
1992: Pioneer Venus 1 - USA Venus Orbiter (May 20, 1978 - October 8, 1992) lost contact. Pioneer Venus 1 (also known as Pioneer 12) arrived at Venus on December 4, 1978. It operated continuously from 1978 until October 8, 1992, when contact was lost with the spacecraft. It was expected to burn up in the Venusian atmosphere 6 days later. The orbiter was the first spacecraft to use radar in mapping the planet's surface. The electron field experiment detected radio bursts presumably caused by lightening. No magnetic field was detected. From 1978 to 1988 the amount of sulfur dioxide in the atmosphere decreased by 10%. The reason for this decrease is unknown. Perhaps a large volcano erupted just before the orbiter arrived and the amount of sulfur dioxide slowly declined.