Cause of greatest mass extinctions in history and how smart aliens might use gamma-ray bursters

Welcome! "Alien Life" tracks the latest discoveries and thoughts in the various elements of the famous Drake Equation. You may notice that this and future entries are shorter than usual; career, family and book deal commitments have forced me to cut back some of my projects. Now, here's today's news:
g Stars - What is the habitable zone of the nearby star system Eta Cassiopeiae AB? See article.
g Abodes - A new study shows that changes in sea levels and ocean sediments may be responsible for some of the greatest mass extinctions in history. The research sheds light on the connections between life and the environment of Earth. See article.
g Intelligence - You might expect men and women to look at sexual photographs differently. But a new study unexpectedly found that men are more likely than women to first look at faces rather than other parts of a nude body. See article.
g Message - Regardless of what causes gamma-ray bursters, they could be the key to discovering life elsewhere in the universe. An astrophysicist says smart aliens might use the bursts to alert us to their messages. See article. Note: This article is from 1999.
g Cosmicus - A new technique has been developed to identify organic matter in soils using ultraviolet light. The technology could be useful in the search for signs of life on Mars. See article.
g Learning - This retrospective highlights Arthur C. Clarke’s influence on space travel, space exploration, and astrobiology. See article.
g Imagining - Like first contact stories? Then be sure to read Harry Turtledove's novel "A World of Difference," published by Del Rey in 1990.
g Aftermath - What role will extraterrestrials play in humanity’s future? See this paper by University of Toronto Professor Allen Tough. Though written more than 20 years ago, the paper contains plenty of useful ideas that are fresh (and ignored) today, especially those about extraterrestrial behavior and help.