Houston has sports teams for every major professional league except the National Hockey League (NHL). The Houston Astros are a Major League Baseball (MLB) expansion team formed in 1962 (known as the "Colt .45s" until 1965) that made one World Series appearance in 2005. The Houston Rockets are a National Basketball Association (NBA) franchise based in the city since 1971. They have won two NBA Championships: in 1994 and 1995 under star players Hakeem Olajuwon, Otis Thorpe, Clyde Drexler, Vernon Maxwell, and Kenny Smith. The Houston Texans are a National Football League (NFL) expansion team formed in 2002. The Houston Dynamo are a Major League Soccer (MLS) franchise that has been based in Houston since 2006 after they won two MLS Cup titles in 2006 and 2007. The Houston Dash play in the National Women's Soccer League (NWSL). The Scrap Yard Dawgs, a women's pro softball team, is expected to play in the National Pro Fastpitch (NPF) from 2016.

Answer this question, if possible (if impossible, reply "unanswerable"): When were the Houston Astros dissolved?
unanswerable