* Astronomy

Title: Short-term Effects of Gamma Ray Bursts on Earth
Authors: Osmel Martín (UCLV, Cuba), Douglas Galante (IAG-USP, Brazil), Rolando Cárdenas (UCLV, Cuba), J.E. Horvath (IAG-USP, Brazil)

The aim of the present work is to study the potential short-term atmospheric and biospheric influence of Gamma Ray Bursts on the Earth. We focus in the ultraviolet flash at the planet's surface, which occurs as a result of the retransmission of the \gamma radiation through the atmosphere. This would be the only important short-term effect on life. We mostly consider Archean and Proterozoic eons, and for completeness we also comment on the Phanerozoic. Therefore, in our study we consider atmospheres with oxygen levels ranging from 10^{-5} to 1% of the present atmospheric level, representing different moments in the oxygen rise history. Ecological consequences and some strategies to estimate their importance are outlined.

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Title: Whilst this Planet Has Gone Cycling On: What Role for Periodic Astronomical Phenomena in Large Scale Patterns in the History of Life?
Authors: B.S. Lieberman, A.L. Melott (University of Kansas)

One of the longstanding debates in the history of palaeontology focuses on the issue of whether or not there have been long term cycles (operating over tens of millions of years) in biodiversity and extinction. Here we consider the history of this debate by connecting the skein from Grabau up to 2008. We focus on the evidence for periodicity that has emerged thus far, and conclude that there is indeed some evidence that periodicity may be real, though of course more work is needed. We also comment on possible causal mechanisms, focusing especially on the motion of our solar system in the Galaxy. Moreover, we consider the reasons why some scientists have opposed periodicity over the years. Finally, we consider the significance of this for our understanding of evolution and the history of life.

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The clock is ticking inexorably toward doomsday even if we don't kill ourselves by poisoning the environment or overheating the planet. You see, there's a little problem with the Sun.
The Sun is slowly getting warmer as it burns the hydrogen in its core. In about 5 billion years, the Sun will begin evolving into a bloated red giant. Its outer gas shell will swell up, engulfing the Earth by the time it reaches its peak size and brightness 7 billion years from now.
But long before that, in 1.1 billion years, the Sun will grow 11% brighter, raising average terrestrial temperatures to around 50 °C (120 °F). That will warm the oceans so much that they evaporate without boiling, like a pan of water left on a sunny kitchen counter.

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Evidence suggests that 'sick Earth' extinctions more likely
In geology as in cancer research, the silver bullet theory always gets the headlines and nearly always turns out to be wrong.
For geologists who study mass extinctions, the silver bullet is a giant asteroid plunging to earth.
But an asteroid is the prime suspect only in the most recent of five mass extinctions, said USC earth scientist David Bottjer. The cataclysm 65 million years ago wiped out the dinosaurs.

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