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<TITLE>Planetary Talk Monday Sept. 13 Fred Singer</TITLE>
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<P ALIGN=CENTER><FONT SIZE=2 FACE="Arial">EPS End of Summer Seminar</FONT></P>
<P ALIGN=CENTER><FONT SIZE=2 FACE="Arial">Phobos-Deimos and the Early History of Mars </FONT></P>
<P ALIGN=CENTER><FONT SIZE=2 FACE="Arial">Fred Singer</FONT></P>
<P ALIGN=CENTER><FONT SIZE=2 FACE="Arial">Professor Emeritus, University of Virginia</FONT></P>
<P ALIGN=CENTER><FONT SIZE=2 FACE="Arial">The Martian moons may hold the key to the early history of Mars and the other terrestrial planets. I will present arguments against simple capture and co-formation. To satisfy the time constraints on Mars core formation set by Hf-W isotope arguments, we investigate possible sources of energy to promote early melting of the planet, including gravitational energy of accretion and the radioactive decay energy of Al-26. An additional source is tidal friction, as pointed out long ago by Francis Birch. It leads to a hypothesis for the origin of Phobos and Deimos as the remnants of a much larger original satellite captured by Mars. We discuss dynamic constraints and possible observations to verify the hypothesis.</FONT></P>
<P ALIGN=CENTER><FONT SIZE=2 FACE="Arial">Monday, September 13, 1pm</FONT></P>
<P ALIGN=CENTER><FONT SIZE=2 FACE="Arial">4th floor, Hoffman Laboratory, 20 Oxford St.</FONT></P>
<P ALIGN=CENTER><FONT SIZE=2 FACE="Arial">Directions: </FONT><A HREF="http://www.eps.harvard.edu/directions.php"><U><FONT COLOR="#0000FF" SIZE=2 FACE="Arial">http://www.eps.harvard.edu/directions.php</FONT></U></A></P>
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