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At 6 p.m. ET., a "Million Hoodie March" is set to begin winding through the streets of New York City, from Union Square to the United Nations.

One of the organizers, Daniel Maree, told News One that the march was intended to protest "the absurdity of Trayvon [Martin's] murder."

There's a small spacecraft called Messenger that's been orbiting the planet Mercury for a year. Today, at the Lunar and Planetary Science Conference in Houston, astronomers revealed what they've learned about the innermost planet in our solar system, and some of the new knowledge is puzzling.

Maria Zuber, a planetary scientist at the Massachusetts Institute of Technology, studied a large crater 900 miles across called Caloris.

For the first time, the U.S. Supreme Court has ruled that defendants have a constitutional right to effective assistance of counsel in plea bargains. In a 5-4 decision Wednesday, the court went further, declaring that when a lawyer acts unethically or gives clearly wrong advice, the defendant may be entitled to a second chance at accepting a plea offer.

My sister is no science writer, and I'm no baker, but recently our worlds melded in a surprising way.

Here's what happened: Last October, I attended a workshop on artisanal bread and cheese-making at Salt Water Farms in Lincolnville, Maine. Farm manager Ladleah Dunn introduced us to the concept of making sourdough bread with levain, or starter, instead of packaged yeast.

Dutch lawmakers are calling for a parliamentary hearing, today, after new allegations of abuse by the Catholic Church surfaced over the weekend. This time, an investigation by the newspaper NRC Handelsblad found that Catholic-run institutions had surgically castrated young boys.

Regular aspirin use might reduce the risk of cancer by as much as 38 percent, according to a big new review of research on the issue. But "might" is the key word here, other scientists say. And even if it works, that benefit comes with costs, including an increased risk of ulcers and internal bleeding.

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Former U.N. Security General Kofi Annan got a boost today from the Security Council as he struggles to resolve the crisis in Syria. The council endorsed his peace proposals. They call for a daily two-hour pause in fighting to allow humanitarian aid in and for a political dialogue between the Syrian government and the opposition. Here's NPR's Michele Kelemen.

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In women's college basketball the Sweet 16 is set. And to no one's surprise, the four number one seeds have made it. Can any team beat Baylor, Stanford, Yukon or Notre Dame? Or will those four keep rolling until the Final Four?

Joining me is NPR's sports correspondent Tom Goldman. Welcome back, Tom.

TOM GOLDMAN, BYLINE: Thank you.

The sweeping health overhaul law turns 2 years old this Friday. And as it heads toward a constitutional showdown at the Supreme Court next week, the debate over the measure remains almost as heated as the day President Obama signed it into law.

The standoff between a murder suspect and French police in Toulouse, France, has stirred up a swirl of speculation about the man's background and motives, but so far there are relatively few confirmed facts.

French officials say the suspect is a 23- or 24-year-old Frenchman of Algerian decent by the name of Mohammed Merah, who had a long record as a juvenile delinquent.

He's suspected in the killings this month of three French paratroopers of North African descent, as well as a rabbi and three Jewish schoolchildren.

Saying that Mitt Romney may not be able to "grind his way toward the nomination" despite a huge fundraising advantage, former House Speaker Newt Gingrich told NPR today that he sees no reason to exit the Republican presidential race and that there's a chance of a new contender emerging at the party's convention in August.

"I'm not so sure you wouldn't get a series of brand new players" stepping forward during a brokered convention, he told Morning Edition co-host Steve Inskeep.

The Denver Broncos have traded quarterback Tim Tebow to the New York Jets in exchange for a fourth-round and a sixth-round draft pick, Newsday is reporting.

Tebow became redundant in Denver after the team signed Peyton Manning to a five-year, $96 million contract. Newsday adds:

New Orleans Saints head coach Sean Payton has been "suspended for one season without pay for his involvement in the team's bounty program," NFL.com reports.

The team's former defensive coordinator, Gregg Williams, "has been suspended indefinitely." He ran the program that paid players bounties for hits that knocked opponents out of games. Williams left the Saints after last season to join the St. Louis Rams.

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NEAL CONAN, HOST:

This is TALK OF THE NATION. I'm Neal Conan in Washington. Romney recovers in Puerto Rico and romps in Illinois. House Republicans draw a line. Santorum wants a do-over, maybe in Louisiana. It's Wednesday and time for a...

RICK SANTORUM: Saddle up...

CONAN: ...edition of the Political Junkie.

PRESIDENT RONALD REAGAN: There you go again.

VICE PRESIDENT WALTER MONDALE: When I hear your new ideas, I'm reminded of that ad: Where's the beef?

SENATOR BARRY GOLDWATER: Extremism in the defense of liberty is no vice.