We show that the escape of hydrogen from early Earth's atmosphere likely occurred at rates slower by two orders of magnitude than previously thought. The balance between slow hydrogen escape and volcanic outgassing could have maintained a hydrogen mixing ratio of more than 30%. The production of prebiotic organic compounds in such an atmosphere would have been more efficient than either exogeno...

■ Abstract In 1997, after almost forty years since the initial attempt by Benioff et al (1959), continuous free oscillations of the Earth were discovered. Spheroidal fundamental modes between 2 and 7 millihertz are excited continuously with acceleration amplitudes of about 0.3–0.5 nanogals. The signal is now commonly found in virtually all data recorded by STS-1 type broadband seismometers at q...

Compared to Earth’s atmosphere, Mars has a thin CO2-rich atmosphere with a surface pressure of about 700 Pa. When normalized to planetary mass (mass of Mars is 10.7% of that of Earth), the abundance of volatiles on Mars is about 0.07% to 6% of that on Earth (when CO2 in terrestrial carbonates is included). Is the depletion of volatiles on Mars a primary feature (because less volatiles accreted ...

Form for the 2012 SORCE Science Meeting – Annapolis, MD, Sept. 18-19 Models of Spectral Irradiance Variability Origins in the solar atmosphere and impacts on Earth’s atmosphere Session Themes (identify your preference if you have a preference): _____ 1. Modeling of the solar atmosphere with emphasis on spectral irradiance _____ 2. Modeling of the solar influence on Earth climate _____ 3. Observ...

The Earth formed through accretion of planetesimals in 1–100 million years. Planetesimal impacts induce degassing, melting, and vaporization during accretion. The impact degassing, as well as the gravitational capture of the surrounding solar nebula gas, formed the proto-atmosphere on a growing Earth. The impact of heating and the blanketing effect of the proto-atmosphere resulted in the meltin...

New observations and derived chemical abundances are reported for a sample of 57 bulge planetary nebulae (PN). Together with our previous results, a total of over a hundred objects have been analyzed, which constitute one of the largest samples of bulge nebulae studied under homogeneous conditions, including equipment and reduction procedures. In general, our data show a good agreement with som...

Introduction. During the end stage of planet formation , terrestrial planets are expected to experience a number of giant impacts. Understanding how much of the planet's atmosphere is lost to space during such collisions is vital to be able to determine the origin and evolution of planetary atmospheres. Recently, geo-chemical observations [1, 2] and high angular momentum models for the Moon-for...

As part of its strategic plan, the National Aeronautics and Space Administration (NASA) formulated the goal of “utilizing the knowledge of the Sun, Earth and other planetary bodies to develop predictive environmental, climate, and natural resource models to help ensure sustainable development, and improve the quality of life on Earth” (NASA 1998). We know now that, over geologic periods, the ea...