Fast Facts:

  • second planet from the Sun
  • average distance from the Sun is 108 million km
  • average temperature is 480 degrees Celsius
  • diameter at equator is 12,104km
  • no moons
  • length of day is 243 Earth days
  • length of year is 225 Earth days
  • atmosphere is mainly made up of carbon dioxide
  • nearest distance to Earth is 42 million km

The picture shows the impact crater Riley (named after Margaretta Riley, a 19th Century botanist). The crater is 25 kilometers in diameter. The floor of the crater is 580 meters  below the plains surrounding the crater. The crater's rim rises 620 meters above the plains and 1,200 meters  above the crater floor. The crater's central peak is 536 meters  high.
Image Credit: NASA/JPL/Northwestern University

The view is to the northeast at the center of an area containing seven circular dome-like hills. The average diameter of the hills is 25 kilometers  with maximum heights of 750 metres. Three of the hills are visible in the center of the image. Fractures on the surrounding plains are both older and younger than the domes. The hills may be the result of viscous or thick eruptions of lava coming from a vent on the relatively level ground, allowing the lava to flow in an even lateral pattern. The concentric and radial fracture patterns on their surfaces suggests that a chilled outer layer formed, then further intrusion in the interior stretched the surface. An alternative interpretation is that domes are the result of shallow intrusions of molten lava, causing the surface to rise. If they are intrusive, then magma withdrawal near the end of the eruptions produced the fractures. The bright margins possibly indicate the presence of rock debris or talus at the slopes of the domes.

Image Credit: NASA/JPL/Northwestern University