What is a Moon?

We now have the most impressive picture ever taken of Phobos, which circles Mars.

It’s a rock.  Nothing but a rock.  Granted it’s a big rock.  But, it’s still just a rock.  Is that a moon?  Is anything that orbits a planet truly a moon?  Is there some more definitive definition of a moon?  By the existing definition, Earth has probably 8,000 moons by now, with 7,999 being man-made objects.

That’s an asteroid called “Annefrank”.  It looks a lot like Phobos.  If “Annefrank” suddenly started circling a planet, it would no longer be an asteroid, it would be a moon.  So, you could come to the conclusion that moons are objects that serve no other purpose than to just circle a planet.  However:

That’s Titan, which circles Saturn.  It’s got color, it’s got an atmosphere, and taking a leap of faith, it could support life.

That’s the surface of Europa, which circles Jupiter.  That’s ice you see there, evidence of the basic element needed to support life.  Speculation is life might exist under the frozen shell.

And Io, which looks a lot like a planet.  Less likely to support life, but still has a lot of features a planet would.

What I’m leading to is physically the only difference in definition between a moon and a planet is what it orbits.  That worked fine 100 years ago, but in lieu of being able to actually visit these places, and becoming very familiar with the differences moons have, I would like to see a better definition of what constitutes moons and planets.  If there’s life out there, who cares what it orbits?  To me a moon is something not likely to support life, a planet should have some physical characteristics to define it could support life, such as an atmosphere.  Io and Europa are more of a planet than they are a moon.  Annefrank is as much a moon as Phobos is.  When someone says something is a moon, I’d like to have a clear visualization and expectation of what it is.  If they say something’s a planet, I’d like to know I could get excited about it.

Just another useless rant from Moon, who has a lot of atmosphere.

Life on Europa?

While NASA is busy as heck driving rovers all over Mars trying to find some itsy bitsy evidence of life or history of life, they could be looking in the wrong place.

“Life” seems to thrive more readily in hotter climates than cold. Maybe we should look at Venus a little closer? Also, the turbulent climate of Europa is much more similar to the National Geographic discoveries than Mars. An ice covering with subterranean volcanoes would heat the European underworld enough to sustain life. I imagine it looks more like those National Geographic pics too. We can see the surface of Mars from Earth, we can’t see what’s under the ice of Europa. I wanna look there before spending any more money or effort on Mercury.