I've never trade futures, so bear with me. I noticed that some futures markets have unusual trading hours. For instance, E-mini S&P 500 Futures & Options are traded from 15:30 to 16:30 and then from 17:00 to 15:15. I'm just curious why there's a separate, 1-hour session each day, rather than just one long session like most futures markets or stock markets. Is there much difference in terms of volume, volatility, and market participants between the one-hour session and the other session? Thanks.