A little advance notice


Okay, everyone, take heed. Friday, September 15th is International Dive Into A Gas Giant Day! NASA is celebrating by sending its orbital probe Cassini down into the atmosphere of Saturn, which it has been taking photos of for the past thirteen years. This could be encouraging to many people out there, since it shows that perseverance may pay off: it took over a decade of lurking and spying, but Cassini is finally going to gain entry.

Meanwhile, I’m trying to give you some time to prepare, since finding a way to celebrate Dive Into A Gas Giant Day might prove a little challenging. While we have a few select gas giants on Earth, I’m not suggesting that anyone should even attempt to dive into them; I’d recommend keeping as much distance as possible, actually. Which means avoiding 1211 Avenue of the Americas in Manhattan…

Okay, yeah, I’ve been doing a fake holiday every month, and I don’t think Dive Into A Gas Giant Day is going to catch on. But the event is real; Cassini will enter Saturn’s atmosphere on Friday, the end of a long and remarkably productive mission. We’ve seen more detail about Saturn itself and its curious hexagonal polar storm, its various rings, and the makeup of quite a few of its moons – the probe, in fact, found seven more moons during its mission, and might even have witnessed the birth of another. And Enceladus is a relatively promising candidate for extraterrestrial life, if we find a way to get past the ice layer.

Now, if you look at the dates of the mission, you might find fault with NASA and JPL, since the plunge is going to take place exactly one month shy of the twentieth anniversary of the launch – wait a second; didn’t I just say “thirteen years?” Now, c’mon, think about it – Cassini was launched 20 years ago, but it took seven just to get to Saturn, probably because the GPS satellites are in orbit only around Earth, and who you gonna ask for directions out there? But that’s orbital mechanics for you, for both aspects, really. Cassini had to do a few flybys to get itself out to Saturn, and decaying its orbit to get it to enter Saturn’s atmosphere takes a bit of juggling – it’s been in process for years, in fact. Mucking about with this just to make a meaningless anniversary isn’t really worth the effort, if it was possible at all. Remember, Cassini is out there to gather information about Saturn, its rings, and its moons, and this requires some pretty careful orbital mechanics. You can’t just aim for a moon and flit off there – you have to adjust an oblong orbit to intercept a moon as it trundles past on its own circuit.

Are we going to see something really cool as Cassini enters Saturn’s cloud tops? Well, there might be some detailed approach images, but chances are once it gets close everything is going to become a monochromatic haze, and once it ‘enters’ these clouds (there’s likely no firm demarcation, just an increasing density,) the light will drop to nothing quickly, and as the gases thicken Cassini will simply fail and break up. While there might be a solid core deep within, Cassini will be toast long before it could ever reach it.

While I close with an image of Saturn’s moon Mimas against the rings, I’ll leave you with a couple of links. The two images here and eight others can be found at this link, with another ten from 2015 at this one. The mission finale is already linked at top, but the broad overview of Cassini’s history can be found here. And finally, the coolest image of its history, without argument, can be found here – be sure to click on it for the high-resolution version.

Enjoy the holiday!


UPDATE: Astronomy Picture of the Day today has a virtual animation of flying around Saturn, based on Cassini images. For some reason it starts in the middle, so you might want to click on the player and take it back to the beginning, but I admit the impressive stuff doesn’t start until that middle point. Bear in mind that Cassini didn’t actually fly these paths – it’s all computer trickery. But the images that they’re based on is real.

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