After a 2.2 billion mile journey that took seven years, the Cassini-Huygens spacecraft entered the orbit of Saturn, and immediately began sending back data--the closest ever measurements of the ringed planet. In this hour, we'll talk about the mission and what scientists hope to learn.

Plus, Ronald Reagan's death brought renewed attention to Alzheimer's disease, and a call by his widow Nancy Reagan to increase research on stem cells. But how realistic are hopes for a cure based on stem cell technologies? Are conventional drugs still the best hope for treatment? In this hour, we'll get an update on Alzheimer's disease and treatment. New drugs now in clinical trials attempt to combat the disease by stopping the formation of the 'plaques' characteristic of Alzheimer's.

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