The Surface of Venus

Venus was bombarded by meteoroids in the past much like Earth was.  We know this by looking at Mercury, Earth, the Moon, and Mars.  They were all pelted continuously by asteroids and comets that left behind craters when they impacted the surfaces.  But why don't we see many craters on Venus?

The main reason is volcanism.  There are three objects in the solar system with active volcanism: Earth, Venus, and Jupiter's moon Io.  There is evidence that both Mars and minor planet Vesta had volcanism in the past, but now are dormant bodies.  On Venus, the volcanism is ongoing; this is evidenced by the amount of sulfur compounds in the atmosphere.  The volcanism is continually reshaping the surface of Venus, much like it does on Earth.  On Venus, the volcanism can lead to interesting features.

The first are flat-topped mountains called farra.  On Earth, volcanoes form calderas and spew forth lava which can make the volcano taller, or in most cases, widen the base of the volcano.  Farra, on the other hand, are tall (100 m to 1000 m high), but very wide (20 km to 50 km).

 

 

There are also features called novae.  They get the name from the star-like appearance they take on.  The nova are fractures emanating radially from a central region.

 

There are coronae.  These are concentric circles centered on a central depression.

 

 

 

Finally, there are arachnoids.  These are spiderweb like features that combine the look of novae and coronae.

 

 

Venus also has two main landmasses, similar to continents on Earth.  They are Ishtar Terra, named after the Babylonian goddess of love and Aphrodite Terra, after the Greek goddess of love.  It is on Ishtar Terra where we find the the taller mountain on Venus, Maxwell Montes, 11 km tall (above average elevation, what we refer to as sea level).  Note that Mount Everest is only 8.85 km tall.  The weaker gravity on Venus allowed Maxwell Montes to grow taller.  We will see the largest mountain in the solar system on Mars, with weaker gravity than both Earth and Venus.  Maxwell Montes is named after the physicist James Clerk Maxwell who is well known for his laws of electricity and magnetism.  Using his four equations, he was able to predict the existence of radio waves, electromagnetic radiation with the longest wavelengths.  Using radio waves, scientists were able to determine what the surface of Venus looks like.  Maxwell Montes is one of the four features on Venus not named after a female; mythological or historical.  The other three features are:

• Alpha Regio: a tessera in the southern hemisphere
  
• Beta Regio: a volcanic rise in the northern hemisphere
  
• Ovda Regio: the western portion of Aphrodite Terrra that has a complex surface dominated by a large caldera in the far west
  

All of these features were formed by volcanism.

Next time, we will learn about the atmosphere on Venus.