NASA will reveal a "major science finding" about Mars at 11:00 AM (ET) today, but don't expect alien fossils. Rather, the space agency will likely explain how channels called "recursive slope lineae" form on the sides of Martian slopes over time. While that may sound dull, such "dark slope streaks" are one of the red planet's most mysterious features. Most scientists think they're caused by flowing saltwater, since they only happen on sun-facing hills that have surface temperatures above freezing. Flowing water on Mars would be a big deal, of course, since it could support primitive forms of life.