50, 100 and 150 Years Ago; April 2009; Scientific American Magazine; by Daniel C. Schlenoff; 1 Page(s)

PLANET OR ESCAPEE?¿ ¿In their relatively brief acquaintance with Pluto, astronomers have begun to doubt that this object is a planet at all. Pluto¿s eccentric orbit is tilted at a considerable angle to the plane of the ecliptic, in which the orbits of the other planets lie. Even on its closest approach to our region of the solar system, it will shine no brighter than Triton, one of Neptune¿s two satellites, suggesting that it is no larger. There is suspicion that Pluto is an illegitimate offspring of Neptune, a satellite that escaped, as two manmade satellites recently did, to ply its own orbit around the sun. ¿Owen Gingerich"

THE DEEPEST HOLE¿ ¿The crust of the earth is a relatively thin film over the earth¿s interior. Its average thickness is some 10 miles, a mere 400th of the earth¿s radius. Beneath the crust lies the mantle; important details of its composition and character are uncertain. These can only be determined by direct examination. The boundary betweencrust and mantle is the Mohorovicic discontinuity, known to earth scientists as the Moho. To obtain a sample of the mantle, we must drill a hole through the Moho: a Mohole. ¿William Bascom¿