Triton, moon of Neptune

Neptune's largest moon.
14 R_N from Neptune.
6 day orbital period backwards .
Retrograde orbit suggests it was captured by Neptune.

Radius ~ 0.78 R_moon.
Mass ~ 0.39 M_moon (use space probe path to find).
What is Triton's density? To find out, we need to know how to compute a density. Then we compute

The density of water is 1000 kg/m³.
The density of rock is 3000 kg/m³ more or less.
The density of the moon is 3300 kg/m³.

We could conclude that the moon is mostly made of rock.

The density of the earth is about 5500 kg/m³.

That tells us that the rock in the middle of the earth is compressed, making it more dense.
It also tells us that there is a lot of iron in the middle of the earth.

Triton is less dense than the moon.
We conclude that Triton is made of rock and ice.
Temperature: 37 K (that's on the Kelvin scale.)

That's cold.

Here is the south pole region

There are few craters.

Our moon has lots of craters.
Triton has a little atmosphere, but it is not nearly enough to protect it from big rocks hitting and making craters.
This suggests that Triton has been ``repaved'' since whenever there may have been lots of rocks hitting it.

Here is another region, close up.

Few craters: young surface.
Scarps and cracks on ice surface.
- At this temperature, ice is more rigid than ice on Earth.
Very flat areas suggest that these areas were once liquid water.

Here is a closeup of the south polar region.

Davison E. Soper, Institute of Theoretical Science, University of Oregon, Eugene OR 97403 USA soper@bovine.uoregon.edu