YTTRIUM EARTHS.

Melting in super-earths.

We examine the possible extent of melting in rock-iron super-earths, focusing on those in the habitable zone. We consider the energetics of accretion and core formation, the timescale of cooling and its dependence on viscosity and partial melting, thermal regulation via the temperature dependence of viscosity, and the melting curves of rock and iron components at the ultra-high pressures charac...

Extractive metallurgy of rare earths

Although most of the rare earth metals were discovered in Sweden, the industrialisation started in the Austrian Empire. This was due to the fact that the Swedish chemist Jons Fridrik Bahr (1815–1875) from Uppsala went to Heidelberg in Germany in 1855 to analyse some rare earth minerals by the spectroscope discovered recently by chemistry professor Robert Bunsen (1811– 1899) and his colleague ph...

The two earths of Eratosthenes.

In the third century B.C.E., Eratosthenes of Cyrene made a famous measurement of the circumference of the Earth. This was not the first such measurement, but it is the earliest for which significant details are preserved. Cleomedes gives a short account of Eratosthenes' method, his numerical assumptions, and the final result of 250,000 stades. However, many ancient sources attribute to Eratosth...

How Many Earths Are Enough?

The goals of NASA’s Terrestrial Planet Finder (TPF) and ESA’s Darwin missions are to find and characterize terrestrial planets in the habitable zones of other stars, and to search for evidence of life in the atmospheres of any planets found. A key issue that must be addressed is the size of the sample of stars that must be searched before the scientific community, the funding agencies, and the ...

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