Planet theorists are putting up a valiant fight against new findings, but in some cases, the evidence seems to be winning.

Moon.  “New research provokes more questions about the origin of the moon,” blazes a headline on PhysOrg from last month.  For some time now, the “favored scenario” for our moon’s origin has been that a Mars-size body impacted the earth, and the moon formed from the debris.  Scientists even gave a mythical name to the impactor: Theia.  Trouble is, Theia might really be just a myth:

Now, new research from geophysical scientist Junjun Zhang and colleagues, suggests that such thinking might be wrong. In their paper published in Nature Geoscience, they find that in comparing titanium isotopes from both the moon and the Earth, that the match is too close to support the theory that the moon could have been made partly of material from another planet.

The match of isotopes between Earth and moon is too close to believe that a distant impactor brought material from elsewhere.  But it is even more implausible to imagine Earth spinning so fast to throw off some of its material to form the moon.  This leaves mythmakers in an a-musing paradox: “Hopefully new research will one day provide us with a definitive answer. Until that day though, it seems we will all have to just keep on musing.”

Mars:  The dry-Marsers scored more points over the wet-Marsers this month.  In Nature News (April 11),  Eric Hand wrote an article entitled, “Dreams of water on Mars evaporate:  Climate models reveal the red planet was mostly cold and dry.”  The pendulum has swung back to the dry-Marsers:

Last month, Jim Head, a planetary scientist at Brown University in Providence, Rhode Island, threw a wet blanket on the idea that Mars was ever very wet at all, in a keynote talk at the Lunar and Planetary Science Conference in The Woodlands, Texas. Head and others are assembling a picture of a Mars that was cold and dry from the beginning, punctuated at most by short bursts of wetness. “The notion of a palm-tree-covered Mars has waned,” says Stephen Clifford, a planetary scientist at the Lunar and Planetary Institute in Houston, Texas, who is organizing a conference in May on the early climate of Mars….

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