The flux density measured at satellite altitude with a fixed field of view radiometer differs from the true flux density reflected by the earth-atmosphere system within the field of view of the radiometer. This difference is due to angular response characteristics ofthe radiometer, solid angle effects due to geometry, and angular reflectance effects of the earth-atmosphere system. All of these ...

Tian et al. (Reports, 13 May 2005, p. 1014) proposed a hydrogen-rich early atmosphere with slow hydrogen escape from a cold thermosphere. However, their model neglects the ultraviolet absorption of all gases other than H2. The model also neglects Earth's magnetic field, which affects the temperature and density of ions and promotes nonthermal escape of neutral hydrogen.

D. Fernández-Prieto1, J. Kesselmeier2, M. Ellis3, M. Marconcini4, A. Reissell5, and T. Suni5 1European Space Agency, ESRIN, Via Galileo Galilei, 00044, Frascati, Italy 2Max Planck Institute for Chemistry, Hahn-Meitner-Weg 1 55128 Mainz 3BGS Science Programme, UK 4Deutsches Zentrum für Luftund Raumfahrt (DLR), German Aerospace Center, Oberpfaffenhofen, 82234 Wessling, Germany 5iLEAPS Internation...

Michael J. Pook*, James S. Risbey, Caroline C. Ummenhofer, Peter R. Briggs and Timothy J. Cohen 1 Commonwealth Scientific and Industrial Research Organisation Oceans and Atmosphere, Hobart, TAS, Australia 2 Department of Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, MA, USA 3 Commonwealth Scientific and Industrial Research Organisation Oceans and Atmosphere, Canberra,...

All three terrestrial planets with atmospheres support O3 layers of some thickness. While currently only that of Earth is substantial enough to be climatically significant, we hypothesize that ancient Mars may also have supported a thick O3 layer during volcanically quiescent periods when the atmosphere was oxidizing. To characterize such an O3 layer and determine the significance of its feedba...

The diversity of extrasolar planets discovered in the last decade shows that we should not be constrained to look for life in environments similar to early or present-day Earth. Super-Earth exoplanets are being discovered with increasing frequency, and some will be able to retain a stable, hydrogen-dominated atmosphere. We explore the possibilities for photosynthesis on a rocky planet with a th...

Recent attempts to resolve the faint young Sun paradox have focused on an early Earth atmosphere with elevated levels of the greenhouse gases methane (CH(4)) and carbon dioxide (CO(2)) that could have provided adequate warming to Earth's surface. On Titan, the photolysis of CH(4) has been shown to create a thick haze layer that cools its surface. Unlike Titan, however, early Earth's atmosphere ...

If strange quark matter is stable in small lumps, we expect to find such lumps, called “strangelets”, on Earth due to a steady flux in cosmic rays. Based on recent model predictions for this flux, we find that strangelets corresponding to gaseous elements (noble gases, N, and O) accumulate in the atmosphere at high concentration. Metallic and semimetallic strangelets accumulate in suprisingly h...

The build-up of carbon dioxide (CO2) and other greenhouse gases in the Earth’s atmosphere has caused concern about possible global climate change. As a result, international negotiations have produced the Framework Convention on Climate Change (FCCC), completed during the 1992 Earth Summit in Rio de Janeiro. The treaty, which the United States has ratified, calls for the “stabilization of green...