Strange Moons: Mimas....."That's No Moon!"
Mimas was first dicovered by William Herschel in 1789. From that time until Voyager 1 passed by Saturn, it was simply the 7th moon that had been
discovered, and a white dot in astronomer's telescope.
Voyager 1 passed by and imaged Mimas in November, 1980:
The first published pictures of it had everyone joking about it, because of a very good resembelance to a certain fictional piece of movie mania from
"That's no moon! It's a space station." - Obi-Wan, Star Wars: A New Hope
Before we go into that distinct feature on Mimas, first a bit of information about it:
Mimas is only about 415 km wide. Quite small when compared to our own moon.
It has the same surface area as the country of Spain, and has a low density, 1.15 g/cm^3, meaning it's made up mostly of water with a little bit of
rock thrown in.
When the Saturn probe Cassini arrived, it has taken very high resolution images of Mimas:
Some Trivia: Mimas is not actually round, it's more egg shaped, and it's exact dimensions are 415.6 × 393.4 × 381.2 km. The original Death Star from
"Star Wars" is only about 140 km wide. So as small as Mimas is, it's still over 3 times larger than the dreaded Death Star.
The most prominant feature of Mimas is Herschel Crater, that looks like the large dish on the Death Star:
Herschel is 130 km across.
Here's an even closer view of the crater sides. I love how the material has cascaded down the sides of the crater:
As strange as Mimas looks with that large crater, the interesting thing is how many of Saturn's moons also have very large prominant craters:
And Iapetus sports 4 massive ones:
Of course all that tells us is that the solar system was a very violent place during it's first days, and many of these features are ancient.
Saturn's moons do not hold a monopoly of impressive craters. Check out Callisto, one of Jupiter's largest moons:
The multiple rings remind me of a car windshield that got hit with a baseball......
What makes these craters look so impressive is their size as compared to the size of the body they are on.
For example, Herschel crater on Mimas looks darn impressive, but at only 130 km, it's smaller than the impact crater Chicxulub that hit the Earth 65
million years ago, which is 180 km wide!
Still, Herschel looks impressive because of the size ratio to the moon. In order for our planet, Earth to have a crater that had the same ratio, we
would need a crater the same size as Australia!
So what are the largest craters in our solar system? I'll give you the top 3. These are what we call "Confirmed" craters, meaning that astronomers
agree they were formed by impacts:
Number 3: Hellas Planitia, Mars
Hellas Planitia measures in at 2,300 km wide. The basin floor measures at 7,152 meters deep. That is so deep, that scientist think it just might have
enough air pressure at it's bottom for liquid water to exist, given the right conditions.
Number 2: South Pole-Aitken Basin, Earth's Moon
Aitken Basin measures in at 2,500 km wide.
Number 1: Utopia Planitia, Mars
The largest confirmed and recognized crater in the solar system (at this time), is on the planet Mars:
The Utopia Basin measures in at a whopping 3,300 km! That's a 49% crater to body ratio. It's also where the Viking 2 lander touched down.
Trivia Note: in the Star Trek universe, Utopia Planitia is part of the ship building facility that built the original Enterprise, Enterprise-D and F,
and also the USS Voyager.
Okay, so what is the largest "unconfirmed" crater in the Solar system?
That again, goes to Mars. The entire North Polar Basin is theorized to be a impact crater:
The enitre top half of that flat map in the picture above is thought to be a impact basin over 10,600 km wide. Wow, Mars has had a rough time in the
past. Again, however, it's just a theory and has yet to be confirmed.
What about our planet? What's the biggest crater that we can still see?
That would be Vredefort Dome, in South Africa:
It's an impact crater up to 300 km wide. It was made just over 2 billion years ago. Earth may of had larger, but weather, erosion and geology erase a
lot of impact craters here on Earth.
So while Herschel on Mimas is impressive looking........Mars is actually King of the Craters....
edit on 19-9-2013 by eriktheawful because: (no reason given)