No abstract

Changes in the frequency, phase, and amplitude of the Mariner IV radio signal, caused by passage through the atmosphere and ionosphere of Mars, were observed immediately before and after occultation by the planet. Preliminary analysis of these effects has yielded estimates of the refractivity and density of the atmosphere near the surface, the scale height in the atmosphere, and the electron density profile of the Martian ionosphere. The atmospheric density, temperature, and scale height are lower than previously predicted, as are the maximum density, temperature, scale height, and altitude of the ionosphere.

No abstract

A set of significant S band radio occultation measurements was obtained with Mariner 9 during May and June of 1972, for the first time yielding extensive occultation data on the north and south polar regions. The daytime temperature profiles, representative of a clear atmosphere, exhibit gradients (averaging −2.3°K/km) far smaller than those expected under conditions of radiative‐convective balance. The measured gradients are in good agreement with those computed for Stone's radiative dynamical models. The near‐surface temperatures (180°–190°K) measured in the Martian spring daytime on the north polar cap indicate that it may, at least in part, consist of water ice. Temperatures in the south polar area, measured in nighttime, were low enough for condensation of carbon dioxide to take place. Measurements of the height of the daytime ionosphere at solar zenith angles greater than 72° are lower than the expected heights of the ionization peak, possibly indicating about 25% cooling of the lower atmosphere between November and December of 1971 and May and June of 1972. Planetary radii obtained at latitudes ranging from +86° to −80° indicate a pronounced north‐south asymmetry. The south polar region is higher than the north polar area by an average of about 3.4 km; the entire southern hemisphere is 3–4 km higher than the northern hemisphere. A measurement was obtained near the summit of Middle Spot (Pavonis Lacus) showing it to rise about 13.5 km above the surounding terrain.

No abstract

The preliminary analysis of data from the Pioneer 10 S-band radio occultation experinment has revealed the presence of an ionosphere on the Jovian satellite Io (JI) having an electron density peak of about 6 x 10(4) electrons per cubic centimeter at an altitude of approximately 60 to 140 kilometers. This suggests the presence of an atmosphere having a surface number density of about 10(10) to 10(12) per cubic centimeter, corresponding to an atmospheric surface pressure of between 10(-8) and 10(-10) bar, at or below the detection threshold of the Beta Scorpii stellar occultation. A measurement of the atmosphere of Jupiter was obtained down to the level of about 80 millibars, indicating a large temperature increase at about the 20 millibar level, which cannot be explained by the absorption of solar radiation by methane alone and can possibly be due to absorption by particulate matter.

No abstract

Measurements of the frequency, phase, and amplitude of the S-band radio signal of Mariner V as it passed behind Venus were used to obtain the effects of refraction in its atmosphere and ionosphere. Profiles of refractivity, temperature, pressure, and density in the neutral atmosphere, as well as electron density in the daytime ionosphere, are presented. A constant scale height was observed above the tropopause, and the temperature increased with an approximately linear lapse rate below the tropopause to the level at which signal was lost, presumably because heavy defocusing attenuation occurred as critical refraction was approached. An ionosphere having at least two maxima was observed at only 85 kilometers above the tropopause.