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...

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 ...

Abstract Understanding the occurrence of Earth-sized planets in habitable zone Sun-like stars is essential to search for Earth analogs. Yet a lack reliable Kepler detections such has forced many estimates be derived from close-in (2 < P orb 100 days) population, whose radii may have evolved differently under effect atmospheric mass-loss mechanisms. In this work, we compute intrinsic rates su...

The physical characterization of exoplanets will require to take spectra at several orbital positions. For that purpose, a direct imaging capability is necessary. Direct imaging requires an efficient stellar suppression mechanism, associated with an ultrasmooth telescope. We show that before future large space missions (interferometer, 4-8 m class coronograph, external occulter or Fresnel image...

A fundamental question for exoplanet habitability is the long-term stability of the planet’s atmosphere. We numerically solve a one-dimensional multi-component hydrodynamic thermosphere/ionosphere model to examine the thermal and chemical responses of the primary CO2 atmospheres of heavy super Earths (6–10 Earth masses) in the habitable zones of typical low-mass M stars to the enhanced soft X-r...

The analytical potential of a weak-base macroreticular anion-exchange resin for the quantitative separation of metal ions in thiocyanate media is investigated and demonstrated. Distribution data are given for the sorption of some 25 metal ions from aqueous mixtures of potassium thiocyanate (1.0M or less) and 0.5M hydrochloric acid. The magnitude of the distribution data suggests many possible s...

1 2 It is now attested that a large part of the Amazonian rain forest has been cultivated 3 during Pre-Colombian times, using charcoal as an amendment. The incorporation of charcoal 4 to the soil is a starting point for the formation of fertile Amazonian Dark Earths, still selected 5 by Indian people for shifting cultivation. We showed that finely separated charcoal was 6 commonly incorporated ...