Space Part 1: Our Solar System: Saturn

Obligatory Lord of the Rings joke out of they.

Saturn:

Saturn is the second largest planet in our solar system with a diameter of about 74,500 miles it is nearly ten times greater in size than the Earth.  At about 891,000,000 miles (112,000 planet Earths) away from the Sun, it is the sixth planet in our Solar System.

As you can see, Earth is a lot smaller than Saturn.

 Saturn is similar to Jupiter in almost every way: both are made primarily of hydrogen and helium, both have the same internal structure (initial gaseous atmosphere, liquid metallic hydrogen interior layer, rocky/iron core), and both of them have a multitude of moons (next blog post will be on the moons of Saturn).  Saturn however has one feature that no other planet in the Solar System has, a beautiful, large, and complex system of rings.  Now, this is not to suggest that Saturn is the only planet with rings.  Jupiter, Neptune, and Uranus all boast fairly visible ring systems.  None of them however can compare to the sheer immensity and beauty of Saturn's rings.

Jupiter's Rings as imaged by an infrared camera.

As you can you, Jupiter has a well defined ring system.

Uranus' rings

As does Uranus...

Neptune's rings.  Picture taken by Voyager 2

And Neptune...

Here however, are the rings of Saturn

They really are quite incredible and dwarf the rings of every other planet in our Solar System.  Because they are so spectacular, they have been studied extensively by NASA and countless other scientists the world over.

Saturn's Rings, with enhanced color, as imaged by Voyager 2

This image above, shows the true complexity present within Saturn's rings.  As you can see, unlike the other planets, Saturn's rings have many gaps and unique features.  These gaps have caused scientists to label each ring with a letter.

The names are given based on when each ring was discovered, not how far or how close it is to Saturn.   Amazingly, these gaps, in some instances, formed naturally.  Some of the gaps however are the result of some of Saturn's moons.

Known as shepherd moons, Prometheus (top) and Pandora (bottom) literally shepherd this ring, keeping it in place.

As you can see from the above image, two of Saturn's moons (Prometheus and Pandora) are literally shepherding one of Saturn's rings, in the sense that they keep it in place and keep its size relatively constant.  Unusual features such as this are common in Saturn's ring system.

This image above shows another one of these features, the spokes that are present in Saturn's rings.  These black smudges that appear on the rings are actually caused by Saturn's magnetic field interacting with particles inside the rings.  They come and go with predictable regularity and were first discovered when Voyager first flew by Saturn.  Scientists are unsure as to why they darken the areas of the rings that they affect, but research is still being conducted by the Cassini spacecraft imaging team.

Of the billions of objects that make up Saturn's rings, the largest each individual object gets is about the size of large house, so in terms of objects in space, Saturn's rings are made up of very insignificant clumps of water ice.  Scientists have so far been unable to determine the origin of the rings, or how long they have been in existence, or how long they will be around.  This is because the number of collisions between objects is extremely hard to measure, and Saturn's rings are still being fed by outside forces.  More on this later, but Saturn's moons Enceladus is one of the main contributors of mass to the rings, perpetuating their life by countless numbers of years. One final note on the rings, which is demonstrated in the image below, is how skinny Saturn's rings are.  When you look at them directly from the side, they appear to disappear.  This is because the rings themselves are only a few hundred meters thick, minute in comparison to the amount of space the rings themselves take up.  Many people think of the rings as these large objects, and this is because most of the images of the rings are from above or below, so that the rings themselves can be visible.

Thus far, this blog has discussed the rings of Saturn, definitely Saturn's coolest feature.  This is because Saturn is pretty much a smaller clone of Jupiter.  However, there are a few things about Saturn that help to distinguish it from its much bigger brother, Jupiter.  The most obvious of these is Saturn's much less dynamic surface (when compared to Jupiter).  Now, if you read my last blog post, you would know that Jupiter's surface is covered in storms, jet streams, and other random cool features.  Saturn, for the most part, has a pretty static surface.  Jet streams are present, but there are far fewer distinguishable surface features.  However, when there are surface features, they tend to be large and powerful.

This image shows what is called a global storm.  This image was taken by Hubble and shows a storm that goes 2/3 of the way around the entire planet, most of which is hidden by the dark side.

This image shows a storm on Saturn and as you can see, it takes up a large amount of space.  Storms on Saturn have some of the fastest winds in the Solar System, some of them have been clocked at 1,100 miles per hour, nearly twice as fast as the fastest winds on Jupiter.  The simple explanation for this is that there are less things on the planet that cause friction and thus, less things to slow the winds down.  

Speaking of winds, one of the biggest unexplained mysteries of the Solar system is on a part of Saturn that you might not have ever thought about, its north pole.

Saturn's North Pole, image courtesy of Cassini

This is an image of Saturn's hexagonal cloud.  First discovered when Voyager flew by, scientists have no idea why a nearly perfect hexagon is floating on Saturn's north pole.  Even now,over thirty years since it was discovered, scientists have absolutely no idea how this cloud is formed.  It is a permanent fixture on Saturn's surface and the only explanation is that Saturn's magnetic field is interacting with something (possibly Jupiter's magnetic field) to create this amazing shape.  My personal favorite idea for why this exists is that aliens have a power station just underneath the cloud, creating it.  Whatever the explanation, it cannot be denied.  There is a hexagonal cloud on top of Saturn and scientists haven't got a clue as to why it is there (I think this is really cool).  

Saturn is many people's favorite planet, mainly because of its amazing rings.  Take away the rings though, and Saturn is a pretty boring gas giant planet.

Saturn looks kind of lame without the rings to be perfectly honest.

Now Saturn's moons on the the other hand are unbelievably awesome and I will discuss them in great detail in my next blog post.  Thanks so much for reading!!!

Space Part 1: Our Solar System: The Moons of Jupiter

Sorry again for the long breaks in between posts.  I just got a job not to long ago so it has been tough to keep up and that's the excuse I'm using so deal.


Originally I thought I would just mention the moons of Jupiter in my last post.  However after much research, I have decided they are worthy of their own post (as the moons of Saturn probably will be as well).


The Moons of Jupiter:


Currently, Jupiter has 66 known Moons, giving it more than any other planet in the solar system.  These Moons differ greatly in size, shape, mass, and in pretty much every other conceivable way.  This massive diversity within the satellites of Jupiter has caused many astronomers to dub Jupiter as a miniature solar system within our own solar system.


Here in the Western world, many of the "discoveries" of the planets that we know of are quite inaccurate.  Most of the planets had been observed long before many of the Europeans claimed to have discovered them.  However, one discovery that cannot be disputed is the discovery of Jupiter's four largest moons in 1610 by Galileo Galilea.  This is because Galileo himself made such amazing improvements to the telescopes available at the time that, for some time, Galileo was in possession of the most powerful telescopes on the planet.  These allowed him to not only discover the four largest Moons of Jupiter: Ganymede, Io, Callisto and Europa.  These four moons marked the first observation of another body orbiting something besides the Earth or the Sun.  This amazing discovery would eventually change the way people thought about the Solar system and the entirety of space.  He was able to discover this because when he first pointed his telescope at the sky, he only observed three bodies around Jupiter.  Every day, he marked where they appeared around the planet, until one day he observed a fourth body.  He continued to witness the bodies moving in and out of his view as they moved in front of and behind Jupiter.  Upon his discovery, he decided to name them after the lovers and daughters of the Roman God Jupiter.  The four large moons would become known as the Galilean Moons.

From left to right: Io, Europa, Ganymede and Callisto

Io, Europa,Ganymede, and Callisto are the four largest and most interesting Moons that orbit Jupiter.  They offer scientific discoveries abound and human beings plan to explore them much further in the near future.  For now, here are profiles of each of the Galilean Moons (going in descending order by size)

Ganymede - Ganymede is the largest Moon in the Solar system.  With a diameter of 3,273 miles it is about 200 miles wider than the Planet Mercury.  This behemoth of a moon is also the only moon known to create its own magnetic field, due to its size and the internal heat caused by convection with Ganymede's liquid iron core (very simply, hot matter rising up to the surface from within the planet and colder matter sinking gravitationally into the planet).  This is because Ganymede is also a fully differentiated body, meaning that there are distinct layers present within the entirety of the planet.  Much like here the Earth, where we have an outer crust and than layers of different substances culminating in an iron core, Ganymede follows this same pattern.  Of the Galilean Moons, Ganymede is the third out from Jupiter (665,000 miles or about 2.5 times the distance our Moon is from the Earth), taking about 7 days to make one complete orbit of Jupiter.  This Moon is pockmarked by impact craters and strange geological features.

This is an actual image of Ganymede.  While technically the color was computer generated, Scientists at NASA believe that this is how Ganymede would actually look.

Due to tidal forces imparted by Jupiter onto Ganymede, the surface of the moon has been continually changed throughout the course of its life.  Ganymede is composed of about half silicate rock and half water ice, meaning that although it is wider than the planet Mercury, it is only about half as massive.  To date, few spacecraft have explored Ganymede in detail, but all of that will change because of the recent announcement of the JUICE spacecraft.  The JUICE (Jupiter Icy Moon Explorer) is a product of the ESA (European Space Agency) and is scheduled to arrive in the Jovian system by 2020.  This spacecraft will give us detailed images of the four Galilean Moons before entering into orbit around Ganymede until it eventually loses power and dies.  JUICE will give us detailed information on pretty much anything you might want to know about the Galilean moons and will provide much more detailed images of the Galilean Moons as well as more detailed scans of Jupiter itself.  When JUICE enters orbit around Ganymede, it will radar map over 99.5% of the surface, giving us one of the most complete maps of the surface of a Moon which is not our own.

Callisto - With a diameter of 2,985 miles, Callisto is the third largest Moon in the Solar System, second largest moon of Jupiter, and is only 47 miles skinnier than the Planet Mercury.  It is the furthest Galilean Moon from Jupiter (1.2 million miles away or about 5 times the distance our moon is from the Earth) and is the only one not tidally heated by Jupiter.  This means that the surface of Callisto isn't really affected by Jupiter's massive amount of energy.  This lack of a tidal forces affecting Callisto has caused its shape to be determined by impacts of objects from space.

Callisto

As you can see from this image, Callisto is covered heavily by craters and in fact, scientists believe it may be the most heavily cratered object in the Solar System.  Due in part to its size, and in part to its proximity to Jupiter.  Because of Jupiter's massive size, it attracts many free floating objects from space.  As they near Jupiter, they often slam into Callisto because, being the furthest away from Jupiter, it is often the first thing encountered by asteroids.  There are so many craters on Callisto, that no matter where a new impact takes place, it can only cover up an already existing crater(s).  Callisto has no past evidence of volcanism or of any other serious geological events.  When scientists first sent the Voyager Spacecrafts into space, they thought that all of Jupiter's Moons would be like Callisto, dead, cold, and covered in a massive amount of craters.  When they arrived, they were surprised at the sheer diversity within the Jovian system.  Callisto, of the Galilean Moons, was the only one that lived up to the expectations.  Callisto, like Ganymede, is composed mostly of silicate rock and ice and while it might be almost the same size as Mercury, it does not even have half the mass.  Interestingly, like many of the rocky bodies in the solar system, scientists believe an ocean of liquid water might exist about 100 km below the surface of Callisto.  While the motto for finding life in space has been find the water, scientists believe that due to the lack of tidal forces from Jupiter and a lack of its own internal heat source, Callisto probably is not as good of a candidate for life as say Europa (Fourth Galilean Moon) or Enceladus (moon of Saturn).

Io - With a diameter of 2,263 miles, Io is the third largest Moon of Jupiter and the fourth largest moon in our solar system.  Io is one of the most dynamic bodies in the solar system.  Not only is Io the most volcanically active body in our solar system, but the tidal forces exerted upon it by Jupiter cause it to stretch and squeeze, constantly changing the entirety of Io's being.

Here is an actual image of Io

As you can see from the picture above, Io appears to be yellow and has a very pockmarked surface.  The yellow color you see is caused by the massive amounts of sulfur that is spewed onto the surface by the many active volcanoes on Io.  Because of the frigid temperatures away from the volcanos, about -300 degrees Fahrenheit, sulfur literally freezes into crystals, sticking to the surface of Io, making it yellow.  The sheer amount of sulfur is due to the 400+ active volcanos present on Io's surface.  To compare, each year the Earth only has about 50-70 volcanoes that could be classified as active (going to erupt within the year).

This image shows new lava flows on the surface of Io.  The two images are of the same place, except that the image on the right was taken two weeks after the image on the left.  This image and the image above were taken by the Galileo spacecraft.  Temperatures near the lava flows can reach 1200 degrees Farenheit, despite the frigid temperatures.

Not only are there more volcanoes on Io than on the Earth, but the eruptions are more frequent and more powerful.  This is due to two main factors: 1. Io has a lot less gravitational force, so lava can be shot about 190 miles into the air, meaning that it affects a larger area; 2. Io is tidally affected by Jupiter's gravitational power. Here on Earth, volcanoes erupt at points along fault lines.  These fault lines are the dividing lines of tectonic plates (pieces of the Earth's crust that are literally bouncing off of each other).  These tectonic plates are able to move so much because of the internal heat generated by the Earth.  On Io however, there is no natural internal heat source.  As I mentioned earlier, the stretching and squeezing of Io is caused by Io orbiting around Jupiter.  These forces are so strong that in places they cause land to shift by over 300 feet at times (For a quick comparison, the largest tide on the Earth is 60 feet, and that is water moving, not land).  This amazing force is what generates the internal heat of Io and as a result, generates the over 400 active volcanoes on its surface.  As if all of this wasn't enough, the Moons Ganymede and Europa add even more power to the shifting landscape of Io; just like Jupiter but on a much smaller scale.  As of now, scientists have been unable to accurately measure the age of Io.  This is because, unlike the other Jovian moons and in fact unlike many other moons in our solar system, Io is not pockmarked by impact craters.  This is because the constant resurfacing of Io by fresh lava flows causes any fresh impact crater to be covered up and lost forever, making Io practically impossible to date accurately.

An image of Io taken as Voyager flew by.  Notice, just above the top of the dark side of the moon, the large explosion of material caused by volcanos on the surface.  There is also another one erupting on the bottom of the dark side of the moon.

Io receives these massive gravitational forces from Jupiter because it is very close to the planet (262,000 miles away, only about 26,000 miles further away than our Moon is from the Earth).  What is amazing, is that because Io is so close and thus so affected by Jupiter, it produces about 400,000 volts of electricity, all of which interacts with the atmosphere and magnetosphere of Jupiter, creating permanent electrical storms in the space between Jupiter and Io.  Io truly is an amazing moon, featuring an amazing amount of unique features.


Europa - Europa has a diameter of about 1,950 miles, making it only 100 miles skinnier than our own moon.  Orbiting about 417,000 (about 1.75 times the distance of our Moon from the Earth) miles away from Jupiter, it is the second closest Galilean moon to Jupiter.  Europa is my personal favorite moon within the Jovian system due almost entirely by the fact that Europa is one of the best candidates for harboring life in the solar system (more on that later).

An image of Europa, taken by the Galileo spacecraft.

As you can see from this picture, Europa is covered in what appears to be deep gashes across the surface.  While not immediately apparent, the surface of Europa is covered entirely by water ice, making it one of the smoothest surfaces of any object in the solar system.  The covering of water ice makes Europa's surface a very dynamic, much like the ice caps here on Earth.  Europa is also almost entirely devoid of impact craters, making it difficult to determine its age.  As you might have guessed, the water ice surface indicates that liquid water could also be present on Europa and in fact, scientists have discovered that there is a heck of a lot.

An inner look at Europa, notice the massive amount of water present under the ice.

This picture is what scientists believe is below the initial layer of ice that covers Europa, an almost continuous ocean of liquid water.  In fact, as the picture below demonstrates, there is more liquid water on Europa than there is on Earth.

Looking at Earth with no water on it is weird.  However, if you couldn't already tell, each blue ball represents the amount of water on each body.  Notice how Europa (on the left) has considerably more water than the Earth.

Amazing yes? I think so.


How do scientists know this water is there? Well, if one glances at the surface of Europa, the similarities between ice floating on top of water on Earth and ice floating on top of water on Europa are quite striking.

Known as chaos features because of their unpredictable and chaotic nature, the ice on Europa's surface is cracked.  This happens because the ice on the surface floats on top of the water below, causing the surface ice to buckle and crash into each other.  The ice on Earth creates very similar features and moves in very similar ways, which in turn makes scientists very excited about the possibility of life on Europa.  Even though water is often thought of as an indicator of the possibility of life, scientists also believe that heat is necessary for life to come into being.  Normally, being so far from the Sun, one would not expect a body such as Europa to have adequate enough heat for life to form.  However scientists believe that the tidal forces imparted by Jupiter onto Europa, another culprit in the cracked surface, could be enough to sustain life.  Because there is internal heat present within Europa, scientists believe a scenario similar to the life at the bottom of our ocean could exist.

A hydrothermal vent colony on the bottom of the Atlantic Ocean.  These red tube worms thrive here at the bottom of the ocean despite being subjected to extreme temperatures, pressure, complete lack of sunlight, proximity to poisonous substances, and general lack of resources.  Scientists believe life might be able to thrive on Europa just like life does on Earth in this way.

The complexity of life found on Earth probably does not exists on Europa, however scientists are hopeful that bacterial life may thrive under the ice on Europa.  These colonies of life might live close to hydrothermal vents present under the ocean, much like the ones on Earth pictured above.  While all of this is purely hypothetical, scientists believe it is on of the best bets at finding life within our own solar system that doesn't exist on Earth.  This possibility has caused scientists on Earth, specifically in Europe, to develop the previously mentioned JUICE spacecraft.  JUICE will hopefully paint a much greater picture of all of the Galilean Moons, specifically, whether or not the moons have life.  In addition to JUICE, NASA is very interested in the possibility of life on Europa.  While the mission is currently on hold due to budgetary constraints, the plans for mission are truly epic.

Whoa!

This little guy is the prototype for the part of the JUICE spacecraft that will hopefully be able to travel in the ocean of Europa.  The plan is to melt down through the ice and deposit this guy in the water where it will have the ability to swim around, take video and pictures, analyze the water, and hopefully determine whether or not life does in fact exist on Europa.  Amazingly, the computer in charge of this thing will not be controlled from Earth at all.  It is programmed to search the water on its own, scan the ocean and rocky bottom of the moon for life, and to make all its own decisions regarding where to go and what actions to perform.  NASA scientists are calling this the most ambitious mission they have ever even thought of, let alone attempted.


The Galilean Moons are incredibly diverse, a scientific goldmine if you will.  However, Jupiter does have 62 other moons that I have yet to mention.  

Pie chart of the total mass of all of the Jovian Moons.  Can't see the color for "all other moons"?  That's because the mass of all the 62 other moons is just .0003% of the total mass orbiting Jupiter.

The other 62 moons of Jupiter are all irregular in shape, meaning that they do not possess enough mass to gravitationally collapse into a sphere.  The largest non-Galilean Moon is Amalthea, a body that is about 155 miles by 90 miles by 80 miles, much smaller than the smallest Galilean Moon Europa.  The smallest non-Galilean moons of Jupiter are even less than 1 km across.

Amalthea, the fifth largest moon of Jupiter as seen from the Galileo spacecraft.

I will now list in order from largest to smallest the rest of the moons of Jupiter.  All of them are relatively unknown to scientists and only a few of them actually have pictures that go beyond a dot of light in space.

Himalia, Thebe, Elara, Pasiphae, Metis, Carme, Sinope, Lysithea, Ananke, Adrastea, Leda, Callirrhoe, Themisto, Praxidiki, Megaclite, Kalyke, Taygete, Iocaste, Autonoe, Isonoe, Eukelade, S/2003 J 5, Chaldene, Aoede, Helike, Harpalyke, Thyone, Hermippe, Euanthe, Eurydome, Carpo, Arche, Erinome, Aitne, Hegemone, S/2003 J 23, S/2003 J 10, S/2003 J 18, S/2003 J 16, Orthosie, Thelxinoe, S/2003 J 3, Pasithee, Euporie, S/2003 J 15, S/2010 J 1, Kore, Cyllene, S/2003 J 4, S/2003 J 19, Kallichore, Kale, Herse, Mneme, S/2003 J 2, Sponde, S/2011 J 2, S/2003 J 9, S/2003 J 12, S/2011 J 1, and finally S/2010 J 2.  In case you were wondering about the numbered moons, they have not been named by their discoverers yet and are thus referred to by their catalog number, which works like this:
S/(year discovered)(around what planet)(what number object found in said year, if it says 2, it was the second object discovered in that year).

All of these moons are grouped into families, mainly by location, shape, and proximity to Jupiter.  These moons are also simply the Moons that have been discovered and classified as Moons.  There are hundreds of other even smaller objects that scientists are unable to classify and which may not even be gravitationally bound to Jupiter. There are also about 16 objects currently up for consideration as new Moons of Jupiter.  The Jovian system is a Solar System in miniature.  The incredible amount of diversity present in this system goes to show how much there is to know and how relatively little we know about our own Solar system.

Thanks for reading! Next up, Saturn!