An unmanned Soviet research probe is orbiting Mars on a research mission to learn more about the planet's climate and soil, the official news agency Tass reported. Phobos II went into orbit Sunday after a six-month, 111-million-mile voyage from Earth, Tass said. The spacecraft is carrying instruments and experiments prepared by 12 countries and the European Space Agency. Soviet officials say the mission will help them prepare for a manned mission to Mars in the early 21st century. Pho-bos II was launched July 12 in an ambitious program to unlock mysteries of the Red Planet and its largest moon, Phobos. Tass said Phobos II is the first spacecraft to orbit Mars. But U.S. officials say American probes orbited Mars during the Viking missions of the 1970s.