Giants of Gas and Ice

astro pt2a003

GIANTS OF GAS AND ICE

We pass by, as if we fly, or if you wish to sail the sky, within your craft a sailboat be, atop the solar sea beside. Remember Apollo 8 and the first picture of “Earth-Rise” beyond the moon. You are farther away now. In the realm of giants!

They are planets, too. And they are big! But it’s not them you want. It is their moons! But first you must navigate through the asteroid belt to reach them. Hundreds of miles of space, just beyond Mars, and thick with shooting stars and meteorites. Come on. You can do it! But be careful. Remember the fate of the dinosaurs.

THE GAS GIANTS

Jupiter is so big, so bright, and so obvious. It seems to float across our night sky. A thousand times bigger than Earth, all of the bodies in the solar system could comfortably fit inside its circumference. But it is a gnarly, gaseous ball. Powerful winds, and lightning with ten times the power of that found on Earth. And the giant, swirling red spot? It is three times the size of Earth. What’s up with that?

The pressure of the planet’s mass of gas is so great that methane is crushed into diamonds and hydrogen becomes molten, metallic, and electric. That is why Jupiter has the most powerful magnetic field of any planet!

And that field is full of plasma torn away from its closest moon, Io, which is constantly fuming in volcanic eruption, drawn out by the sweeping gravitational tides of Jupiter and its other moons. We have seen plumes of yellow, green, and red shades of sulfur thrust out 300 miles into space from Io!

The four largest moons of Jupiter are known as the Galilean Moons. Io, Europa, Ganymede, and Callisto. They are what got Galileo in trouble with the Church. You know, the heresy that planets revolve around the sun and not Earth. Galileo saw the moons first on one side, and then the other side of Jupiter. You can see them yourself tonight in a powerful set of binoculars!

The Church issued an apology in 1992. A little late for Galileo, who died under house arrest in 1642. Although it took 350 years to do it, the Church, like science, can be self- correcting.

And of the Galilean moons, maybe life can be found under the smooth water-ice surface of Europa. You should go look! If you could fly there on a commercial jet, it would take you just 100 years!

Saturn would float on water, so light is this giant ball of gas. But its seven rings are what excite our view. Look at them through an inexpensive telescope. The planet varies its tilt for our visual enjoyment. If its rings were highways, you could drive around one in 258 days! In fact, all of the gas giants have some sort of ring system.

Saturn has many moons. The one that excites us the most is Titan. It is the largest⎯bigger than Mercury⎯and has a dense atmosphere of nitrogen and methane. On its surface are flowing rivers and seas of natural gas, cooled to a temperature of minus 300 degrees. Winds there contain tempting indications of organic material in the surface soil. Alien, for sure, but surely interesting!

THE ICE GIANTS

Something big must have hit Uranus. Instead of rotating on an axis perpendicular to the plane of the solar system, it lies on its side. This was the planet unknown to the ancients. It was discovered by William Herschel with his famous telescope in 1781. And don’t forget his sister, Caroline. Together, they were quite a team.

Neptune is the farthest planet away. That body has a thick atmosphere of hydrogen and helium, with evidence of hydrocarbons, ammonia, and methane. It is methane that gives it a blue color. Its core is composed of various ices and rock. And it is so far away that it takes light four hours to reach us. And that is traveling at 186,000 miles per second! You do the math. The distance will expand your imagination.

Neptune’s largest moon is Triton⎯not Titan, that’s Saturn. Triton is solid, but its core is geologically active. That must mean radioactive decay and internal heat. Maybe there is a buried ocean that is liquid and harbors primitive life forms. Is that why some of the volcanic ejecta contain what may be a black mixture of organic compounds? But Triton’s surface is exceptionally cold, a frozen nitrogen crust at minus 391 degrees Fahrenheit. That is pretty close to absolute zero⎯minus 460 degrees Fahrenheit!

I know that Pluto is still farther out, but so is a lot of other stuff out there. Eris, Haumea, Makemake, Ceres. They are all bodies in the Kuiper Belt or beyond. And many of them are comets! Why, even farther out in interstellar space is the Oort Cloud of icy planetesimals. So we will stop at Neptune for this essay.

So, if you want to get out of here⎯up there, that is⎯maybe there is a Mars, or Titan, or Triton that you might eventually explore. But I think I will stay here and work to take better care of this place. It has been my job for more than 40 years now.

 

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