Ultraviolet spectrometry of the inner solar system from Mariner 10

The significant results of Mariner 10 ultraviolet spectrometer observations of Mercury, the moon, the interplanetary medium, the comet Kohoutek, and Venus are summarized. The total surface pressure on Mercury was found to be less than (1-2) millionths mbar by the occultation experiment. Estimated number densities and upper limits for various species at the surface subsolar point of Mercury were obtained. Preliminary analysis of Kohoutek data shows possible detection of O and C associated with the comet head. Emissions from Lyman alpha in the interplanetary medium show maximum and minimum intensity directions that can be fitted by a model in which the interstellar wind penetrates the heliosphere from a direction of about 252 deg right ascension and -17 deg declination with a velocity of about 20 km/sec. There is evidence for a high-temperature scale height for hydrogen for Venus similar to that reported by Mariner 5.