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PHOTO CAPTION NO.: STScI-PRC95-16
EMBARGOED UNTIL: 2:00 P.M. March 21, 1995


VENUS CLOUD TOPS VIEWED BY HUBBLE


This is a NASA Hubble Space Telescope ultraviolet-light image of the
planet Venus, taken on January 24 1995, when Venus was at a distance of
70.6 million miles (113.6 million kilometers) from Earth.

Venus is covered with clouds made of sulfuric acid, rather than the
water-vapor clouds found on Earth. These clouds permanently shroud
Venus' volcanic surface, which has been radar mapped by spacecraft and
from Earth-based telescope.

At ultraviolet wavelengths cloud patterns become distinctive. In
particular, a horizontal "Y"-shaped cloud feature is visible near the
equator. Similar features were seen from Mariner 10, Pioneer Venus,
and Galileo spacecrafts. This global feature might indicate
atmospheric waves, analogous to high and low pressure cells on Earth.
Bright clouds toward Venus' poles appear to follow latitude lines.

The polar regions are bright, possibly showing a haze of small
particles overlying the main clouds. The dark regions show the
location of enhanced sulfur dioxide near the cloud tops. From previous
missions, astronomers know that such features travel east to west along
with the Venus' prevailing winds, to make a complete circuit around the
planet in four days.

Because Venus is closer to the Sun than Earth, the planet appears to go
through phases, like the Moon. When Venus swings close to Earth the
planet's disk appears to grow in size, but changes from a full disk to
a crescent.

The image was taken with the Wide Field Planetary Camera-2, in PC
mode. False color has been used enhance cloud features.

Credit: L. Esposito (University of Colorado, Boulder), and NASA