It's a good thing moons aren't a measure of worth, because Jupiter would be the coolest
thing floating.
I mean, PLUTO has FIVE!
We've got one.
Just one measly little moon.
A staple of alien worlds in science fiction is multiple moons (or suns), because we lowly
Earthlings have only ever had the one.
The creation of which is a touchy subject, but you can see more on that if you subscribe
and check out my video on it; but why do we keep living moonogamously while planets like
Mars get to take both of their gals for a spin?
We only have one moon because of the way the solar system was formed!
There are two categories of planets, terrestrial and jovian -- the terrestrial planets: Mars,
Earth, Venus and Mercury; only have three moons in TOTAL.
Mars has two, Phobos and Deimos, and we have one The Moon or Luna. Mercury and Venus are
left all alone.
Jovian planets, on the other hand, have scores of moons!
Jupiter has more than 60, Saturn also is over that sextalunar threshold, Uranus has 27,
and Neptune has 14.
New Horizons is getting closer to Pluto as we speak, and imaging Pluto's FIVE moons.
FIVE.
PLUTO IS A DWARF PLANET and it's swinging with more moons than us.
WTF pluto.
We don't know the EXACT reason different planets have different satellites -- the technical
term for a moon -- but planets acquire satellites through one of three possible ways.
ONE, they get smacked by another body that causes a chunk to begin to orbit; TWO, they
capture it using their gravity to snap a passing celestial body.
THREE, they form alongside a planet from an accretion disk.
The first theory is likely how Earth got Luna up there.
The second explains Mars' moons.
Mars is very close to the asteroid belt that sits between the terrestrial and jovian planets;
it could have easily grabbed its proto-planet-sized satellites from there.
It also may explain Pluto's five tiny moons.
Pluto's smallest satellites, Nix and Hydra, are little icy bodies which probably got too
close and were trapped by Pluto's gravity.
The accretion disks in the third theory, vogue with the idea of solar system and planetary
formation.
As a solar system forms, dust gathers, spinning into a disc.
Eventually, gravity pulls the dust and gas together, forming a planet, while any gas
flying around the edge forms planetesimals by coalescing around tiny chunks of ice, rock
or flakes of metal or dust.
Sometimes those planetesimals slam together forming satellites -- which is probably how
Jupiter got so many.
Venus may have had a moon at one point, but a paper from CalTech postulated the yellow
planet suffered an impact which reversed its spin, causing its moon to crash into its surface.
Eventually, the satellite was absorbed and it merged with the planet.
Mercury has no moon because it's so small; and although that didn't stop Pluto or Mars
-- Mercury has the added difficulty of being closest to the Sun.
The solar wind is strong with all us terrestrial planets, blowing away material that might
have formed accretion disk planets, and affecting satellites more than with jovian planets.
The thing is, we only DISCOVERED other moons existed when Galileo spotted Jupiter's four
largest in 1610; these so-called Galilean moons: Io, Europa, Ganymede and Calisto lit
up astronomers' collective imaginations in a fire still burning today.
It was only in the 1970s that we finally confirmed Mercury's LACK of moon, when scientists used
instruments on Mariner 10 to peek at the tiny planet.
As we've learned more about satellites, missions have been proposed to study them and not just
their parent planets.