Divergence of Venus and Earth

5 problems

• Why does Venus have no internally generated magnetic field?

  Open

  Venus has an iron core roughly as large as Earth's but no magnetic field of its own. Either its core does not churn today or something else stops a dynamo (a self-sustaining magnetic generator made by flowing liquid metal).

• Where did the oxygen from Venus's lost water go?

  Open

  If Venus once held much water that sunlight split into hydrogen and oxygen, the light hydrogen escaped to space but most of the heavier oxygen could not. Venus's atmosphere now has almost no free oxygen, so it must have gone somewhere.

• What maintains the superrotation of Venus's atmosphere?

  Partially resolved

  The solid body of Venus turns once every 243 Earth days, but its clouds circle the planet in about 4 days, roughly sixty times faster. Which waves and eddies keep feeding spin into the atmosphere is unresolved.

• What tectonic regime operates on Venus, and was it resurfaced catastrophically?

  Open

  Venus has few craters, spread almost randomly, so its whole surface is only a few hundred million years old. Whether it was repaved all at once or gradually, and how active it is now, is unknown.

• Did Venus ever have surface oceans?

  Contested

  Venus's atmosphere has far more heavy hydrogen than Earth's, a sign that it once held more water that escaped to space. Whether that water was ever a liquid ocean or stayed as steam is unknown.