Earlier today, Majid Shahriari, a professor in nuclear physics at Martyr Beheshti University, was assassinated in Tehran. Fereydoun Abbasi Davani, professor in nuclear physics at Iran's National Defense University, was severely wounded in a separate attack. Motorcyclists either stuck explosives to the physicists' cars as they headed to work, or threw explosives into the cars. These were just the latest attacks--on January 10, 2010, Masoud Ali-Mohammadi, another Iranian physicist, was killed by a remote-controlled bomb as he left his home.

No group has taken responsibility for the assassination attempt, but President Mahmoud Ahmadinejad has blamed "Western governments and the Zionist regime."

There is too much unknown right now. The attacks could be a concerted effort to retard Iran's nuclear progress, or they could be meant to hype Iran's own "terror threat" and provide an excuse to crack down on domestic opposition. The only certainty is that the life expectancy of Iranian nuclear physicists is falling rapidly, and is now almost as low as that of Iran's civil-rights activists, journalists, and public intellectuals.