In this artist's concept, the Cassini spacecraft is seen with the European Space Agency's Huygens probe attached underneath as it approaches Saturn. The European-built space probe Huygens separated from its NASA mothership late Friday to begin a descent to Saturn's largest moon Titan, during which it will sample the atmosphere of Titan. (NASA)

    WASHINGTON, Dec. 24 (Xinhuanet) -- The European-built space probe Huygens separated from its NASA mother probe on Friday to begin a descent to Saturn's largest moon Titan for an on-site study of the atmosphere of Titan.

    NASA said in an online news release that its Deep Space Network tracking stations in Madrid, Spain, and Goldstone, California, received the signal at about 10:24 p.m. EST (0324 GMT).

    Titan is the only moon that has the atmosphere in the Solar system. Its chemistry is believed to be very similar to that of the early Earth before life is formed. And scientists hope the on-site probe by Huygens would confirm the assumption and help them better understand how life appeared on the Earth.

    The trip by Huygens is also expected to answer the question that whether there is any liquid on Titan's surface. Scientists believe there are methane lakes on Titan.

    The 2.7-meter wide Huygens is planned to reach Titan's upper atmosphere on Jan. 14, 2005 and go through the atmosphere in two and a half hours. Three parachutes will slow its descent so that the instruments it carries can have enough time to take detailed readings.

    After reaching the surface of Titan, if it would be solid, Huygens is designed to operate for a brief period of time, possibly only 30 minutes, before its battery power runs out.

    The Huygens probe, designed and built by the European Space Agency, had been carried by NASA's Saturn probe Cassini, which entered the orbit of Saturn on June 30 after a nearly seven-year journey in the space. Enditem