Showing posts from November, 2012

NASA Spacecraft Finds New Evidence for Water Ice on Mercury

Source:   NASA RELEASE 12-411  Excerpt: NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft… has provided compelling support for the long-held hypothesis the planet harbors abundant water ice … within its permanently shadowed polar craters. …"The new data indicate the water ice in Mercury's polar regions, if spread over an area the size of Washington, D.C., would be more than 2 miles thick," said David Lawrence, a MESSENGER participating scientist …. Given its proximity to the sun, Mercury would seem to be an unlikely place to find ice. However, the tilt of Mercury's rotational axis is less than 1 degree, and as a result, there are pockets at the planet's poles that never see sunlight. …MESSENGER's neutron spectrometer provides a measure of average hydrogen concentrations within Mercury's radar-bright regions. Water ice concentrations are derived from the hydrogen measurements….

The Origin of the Moon

Source:  Alex  N. Halliday,  Science: Vol. 338 no. 6110 pp. 1040-1041 DOI: 10.1126/science.1229954 Excerpt: Any successful model of lunar origin has to explain the Moon’s angular momentum and its slightly lower density (than Earth). …The Moon formed relatively late given its size … more than 30 million years after the start of the solar system, whereas most objects this size are predicted to have formed in the first few hundred thousand years. The oldest rocks appear to have formed from a magma ocean, implying an intensely energetic fiery start…. The oxygen isotopic composition of the Moon is identical to that of Earth to within 5 parts per million, whereas that of nearly all asteroidal and planetary objects are different…. The Giant Impact Theory is the … widely accepted current explanation for the Moon’s late, molten start as a low-density object that now contributes most of the angular momentum in the Earth-Moon system. … an Earth when it was about 85 to 90% formed and anothe