Earlier this week, 32-year-old nuclear scientist Mostafa Ahmadi Roshan was killed by a bomb blast on his way to work in Tehran, Iran.

The attack, carried out with a magnetic bomb placed on Roshan's car by a man on a motorcycle, was like something out of a spy novel. In Iran, however, it's very much a reality. Assassins have targeted five Iranian nuclear scientists in the past two years; four of the attacks have succeeded.

One upon a time, the largest glass telescope mirror was 100 inches in diameter. Today, scientists are casting a mirror 27 feet in diameter that will be part of one of the most powerful telescopes on Earth. NPR's Joe Palca speaks with weekends on All Things Considered host Guy Raz from the mirror laboratory, located under the football stadium at the University of Arizona.

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GUY RAZ, HOST:

The captain of the Italian cruise ship which ran aground off the coast of Tuscany last night has been arrested on suspicion of involuntary manslaughter. The majority of the ship's 4,000 passengers reached land by lifeboat, but three people are confirmed dead. About 30 are reportedly injured and some 50 are still unaccounted for. It is still unclear what caused the ship to come so close to the rocky shore.

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SCOTT SIMON, HOST:

This is WEEKEND EDITION from NPR News, I'm Scott Simon. An enormous cruise ship is lying on its side in the Mediterranean today. The Italian ship, Costa Concordia, ran aground off Italy's Tuscan coast, killing at least three people. Passengers described scenes reminiscent of the Titanic. Fabio Costa was working in a shop on the cruise liner when he felt a jolt.

Fresh Air Weekend highlights some of the best interviews and reviews from past weeks, and new program elements specially paced for weekends. Our weekend show emphasizes interviews with writers, filmmakers, actors, and musicians, and often includes excerpts from live in-studio concerts. This week:

Given Lubinda jumped off a bridge this week and popped up smiling.

The widening gulf between the rich and everyone else is a growing source of tension in America.

A new survey from the Pew Research Center finds the income gap is now seen as a bigger source conflict in the U.S. than race, age or national origin. That's why some believe the issue could matter in the presidential campaign, and others worry it would warp the national debate.

Two out of three Americans now perceive strong social conflicts over the income gap — up sharply from two years ago. Paul Taylor of the Pew Research Center has an idea what's behind the increase.

As Guatemala's new president, Otto Perez Molina, takes office today, the former general carries the burden of a complicated history into a new struggle against violence.

The Muslim Brotherhood has emerged as the big winner in Egypt's parliamentary elections. Long oppressed under the regime of Hosni Mubarak, the Islamist party is now the most important power broker in the country. Lourdes Garcia-Navarro reports that the question on everyone's lips now is what does the Brotherhood really represent and how will it govern?

There is a diversity of views in the Republican field for president that is wide, even wild. Host Scott Simon talks with Ross Douthat, a conservative author and New York Times columnist, about the ideological divides in the Republican Party, as apparent in the GOP presidential race.