Protesters headed to the streets and snipers opened fire in Taiz, Yemen today. As The New York Times puts it, the clashes "threatened a day-old cease-fire agreement" and threw into question whether a power transfer agreed to by Yemen's president in November would mean much for the country.

The Times describes the scene:

Scientists have discovered a planet not too much bigger than Earth that's circling a distant star that's much like our own Sun. What's more, this planet is in the so-called "Goldilocks zone" around that star — a region that's not too hot and not too cold. That's the kind of place that could be home to liquid water and maybe even life.

The planet, known as Kepler-22b, is the first near-Earth-sized planet to be found smack dab in the middle of the habitable zone of a twin to our Sun.

A little-noticed trial in Maryland could affect how many dirty tricks voters will see in the upcoming elections — things like anonymous fliers or phone calls telling people to vote on the wrong day, or in the wrong precinct, or that they can't vote at all if they have an outstanding parking ticket.

The tactics are often illegal, but it's rare for anyone to get caught, let alone end up in court.

Today it is widely understood that slavery is a stain on American history — indelible and regrettable. But on the 150th anniversary of the beginning of the Civil War, a new issue of The Atlantic magazine reaches back to a time when this matter wasn't yet settled, and monumental questions were still up in the air: Would slavery continue? Would America remain united?

Hidden in the soil of Illinois and Iowa, a new generation of insect larvae appears to be munching happily on the roots of genetically engineered corn, according to scientists. It's bad news for corn farmers, who paid extra money for this line of corn, counting on the power of its inserted genes to kill those pests. It's also bad news for the biotech company Monsanto, which inserted the larvae-killing gene in the first place.

When businessman Herman Cain left the Republican presidential race over the weekend, he said he would endorse one of his former rivals.

One likely recipient of that endorsement: Former House Speaker Newt Gingrich. Like Cain before him, Gingrich is trying to establish himself as the conservative alternative to former Massachusetts Gov. Mitt Romney. And Cain and Gingrich share a long history of mutual admiration.

In the past two weeks, Russia's president has once again slammed the U.S. for its missile defense plans in Europe. President Dmitry Medvedev told his nation Russia would aim its missiles at U.S. missile interceptors when they are deployed in Europe. He also said Russia might even pull out of the new START agreement, which limits both sides' strategic nuclear warhead deployments. We've heard these complaints and threats before from Moscow. Nevertheless, the tone of the Medvedev's remarks was quite sharp.

Congress returned to Washington Monday with a pile of unfinished business, and no clarity on a path to getting it done. At the top of the congressional to-do list this week is extending a payroll tax holiday that meant about $1,000 in extra take-home pay for the typical family this year. It is set to expire at the end of the month.

Congressional leaders from both parties say the payroll tax cut is a must-pass measure. It's just not entirely clear how it's going to happen.

A decade ago, shortly after the Taliban had been driven out of Afghanistan's capital, Kabul, the international community gathered in Bonn, Germany, to talk about rebuilding Afghanistan.

On Monday, more than 100 countries again gathered in Bonn, this time to see how they could maintain support for Afghanistan after the U.S. and NATO wind down their combat operations in three years.

Afghanistan's president, Hamid Karzai, said he was grateful for all the help his country has received, and he appealed to the international community to keep it up.

GOP presidential candidate Newt Gingrich had little time to savor his weekend appearance atop the Des Moines Register's influential Iowa caucus poll before front-runner reality set in.

The former House Speaker on Monday sparred with fellow candidate Ron Paul over the relevance of businessman/reality show host/would-be debate moderator Donald Trump's opinion.

He was questioned at a New York City fundraiser about the "baggage" he brings to the race.