Two Republicans came out on top in last night's Iowa Caucuses: Mitt Romney and Rick Santorum. But it was close: Romney took the lead with just eight votes. And Santorum's stunning second-place finish has a lot of people talking today. We'll look at how he did it - and why many say he could never win the U.S. presidency.

Plus, avalanches are once again in the news. Two people were killed in the past week and just yesterday four people survived three separate avalanches. Tonight, Mark sits down with a father who lost his son in one of those avalanches. And we'll look at why so many people are willing to take risks in the pursuit of an adrenaline rush, with an extreme snowmobiler who survived an avalanche in B.C.

And there's controversy in the battle against childhood obesity in Georgia. Ads designed to address the state's problem - it has the second highest rate of childhood obesity in the U.S. - are under fire. We'll show them to you tonight. And you'll meet the 11 year-old girl who is one of the faces of the campaign.

Tune in tonight at 8 p.m. ET.