Reflections of megacycle-per-second radio signals by free radicals in Earth's ionosphere are observed having about the intensity predicted for induced magnetic-dipole transitions. It seems that magnetic atoms, ions, and molecules in planetary atmospheres may be detected by this method. These cbservations were made with the topside ionosonder of the Canadian satellite Alouette II.

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...

We solve the integral equation describing the propagation of light in an isothermal plane-parallel atmosphere of optical thickness τ∗, adopting a uniform thermalization parameter ǫ. The solution given by the ALI method, widely used in the field of stellar atmospheres modelling, is compared to the exact solution. Graphs are given that illustrate the accuracy of the ALI solution as a function of ...

THE IMPACT project (Fig. 1), funded by an internal research and development process at Los Alamos National Laboratory (LANL), has the goal to develop an integrated modeling system for addressing current needs in space debris and conjunction analysis for resident space objects (RSOs) in low Earth orbit (LEO). Now, almost three years into the project, we have developed an integrated solution comb...

It is argued that photochemical processes, driven by ultraviolet starlight, could lead to large deuterium fractionation for H2O and CH4 relative to H2 in the primitive solar nebula. Implications for deuterium enrichment observed in planetary atmospheres are briefly discussed.

An iterative method for deducing the general temperature and moisture structure of the troposphere from satellite radiation measurements of medium spectral resolution is described. The temperature and moisture profiles derived from simulated and radiometrically observed radiances, pertaining t o clear atmospheres, are shown to agree favorably with the radiosonde profiles. The method is expanded...

Siphons have been used since ancient times, but exactly how they work is still a matter of debate. In order to elucidate the modus operandi of a siphon, a 1.5 m high siphon was set up in a hypobaric chamber to explore siphon behaviour in a low-pressure environment. When the pressure in the chamber was reduced to about 0.18 atmospheres, a curious waterfall-like feature appeared downstream from t...

Atmospheric oxygen (O(2)) is estimated to have varied greatly throughout Earth's history and has been capable of influencing wildfire activity wherever fuel and ignition sources were present. Fires consume huge quantities of biomass in all ecosystems and play an important role in biogeochemical cycles. This means that understanding the influence of O(2) on past fire activity has far-reaching co...

The effect of aerosols on 14 tropospheric photolysis reactions is examined under noncloudy and cloudy sky conditions by using a detailed one-dimensional radiative transfer model. Pure (NH4)2SO4, pure soot, and internal and external mixtures of the two aerosols, as well as mineral dust aerosol, are considered. Nonabsorbing aerosol generally enhances photolysis rates above and in the upper part o...