A Picture of the Moon's Atmosphere
Abstract
Atomic sodium is a useful tracer of the tenuous lunar atmosphere because of its high efficiency in scattering sunlight at the D_1 (5896 angstroms) and D_2 (5890 angstroms) wavelengths. In 1988, Earth-based instruments revealed the presence of sodium at a density of less than 50 atoms per cubic centimeter at lunar altitudes below 100 kilometers. Telescopic observations that are made with a coronograph technique to block out the disk of the moon allow a true picture of the circumlunar atmosphere to be obtained and show the presence of sodium out to a distance of several lunar radii. The distribution of sodium has a solar zenith angle dependence, suggesting that most of the sodium that reaches great altitudes is liberated from the moon's surface by solar photons (by heating or sputtering) or by solar wind impact, in contrast to a source driven by uniform micrometeor bombardment.
- Publication:
-
Science
- Pub Date:
- July 1993
- DOI:
- 10.1126/science.261.5118.184
- Bibcode:
- 1993Sci...261..184F
- Keywords:
-
- Atmospheric Composition;
- Imaging Techniques;
- Lunar Atmosphere;
- Space Observations (From Earth);
- Astronomical Spectroscopy;
- Coronagraphs;
- Field Of View;
- Sodium;
- Lunar and Planetary Exploration; Moon;
- MOON;
- ATMOSPHERE;
- SODIUM;
- EARTH-BASED OBSERVATIONS;
- DISTRIBUTION;
- DISTANCE;
- ALTITUDE;
- EMISSIONS;
- ESCAPE;
- INTENSITY;
- LATITUDE;
- SHADOW;
- EQUATORIAL REGION;
- POLAR REGION;
- SPECTROSCOPY;
- MORPHOLOGY;
- PROCEDURE;
- BRIGHTNESS;
- DESCRIPTION