The Moon likely accreted from melt and vapor ejected during a cataclysmic collision between Proto-Earth and a Marssized impactor very early in solar system history. The identical W, O, K, and Cr isotope compositions between materials from the Earth and Moon require that the material from the two bodies were well-homogenized during the collision process. As such, the ancient isotopic signatures ...

The solid planets assembled 4.57 Gyr ago during a period of less than 100 Myr, but the bulk of the impact craters we see on the inner planets formed much later, in a narrow time interval between 3.8 and 3.9 Gyr ago, during the so-called Late Heavy Bombardment (LHB). It is not certain what caused the LHB, and it has not been well known whether the impactors were comets or asteroids, but our pres...

relieved, as by sinking a vacant shaft down to it, a violent explosion would follow. The author concluded from Laplace's law of density that the planet Venus has a rigidity equal to that of a corresponding globe of glass, and that the nuclei of all large bodies are effectively of the highest rigidity. The development of pressure as we decend in the globe was shown to be such as to invalidate th...

Electron antineutrinos accompanying the β-decays of long-lived isotopes of uranium, thorium, and potassium in the earth carry information about the quantity and distribution of these geologically important, heat-producing isotopes. This letter discusses terrestrial antineutrino flux measurements at both a continental and an oceanic site. A combined analysis of both measurements provides informa...

Introduction: An overarching geologic theory, GEOMARS, coherently explains many otherwise anomalous aspects of the geological history of Mars [1]. Premises for a theory of martian geologic evolution include: (1) Mars is a water-rich terrestrial planet, (2) terrestrial planets should evolve through progressive stages of dynamical history (accretion, differentiation, tectonism) and mantle convect...

A nearby supernova (SN) explosion in the past can be confirmed by the detection of radioisotopes on Earth that were produced and ejected by the SN. We have now measured a well resolved time profile of the 60Fe concentration in a deep-sea ferromanganese crust and found a highly significant increase 2.8 Myr ago. The amount of 60Fe is compatible with the deposition of ejecta from a SN at a distanc...

Several aspects of mathematical astrobiology are discussed. It is argued that around the time of the origin of life the handedness of biomolecules must have established itself through an instability. Possible pathways of producing a certain handedness include mechanisms involving either autocatalysis or, alternatively, epimerization as governing effects. Concepts for establishing hereditary inf...

Oxygen is the most abundant element in the Earth, constituting about 43 percent by weight of the crust and mantle. While most of this mass is incorporated into silicates, the next most abundant mineral group in the planet is the oxides. The oxide minerals are generally considered to be those oxygen-based minerals that do not contain a distinct polyanionic species such as OH, CO3, SO4 PO4, SiO4,...

The leaching reaction kinetics of weathered crust elution-deposited rare earth with mixed ammonium salts was studied. The in uence of concentration of reagents and particle size of ore on leaching rate was investigated. The results showed that the di usion process and leaching rate could be improved by increasing reagents concentration and decreasing leaching owing rate and particle size. The l...

The initial isotopic compositions of Nd and Sr in basalts from the Central Siberian Plateau and other major continental flood basalts are reported. The continental flood basalts appear to be the product of partial melting of mantle sources that consist of relatively primitive undifferentiated material and are clearly distinct from midocean ridge basalts, which sample mantle reservoirs that have...