Cassini Captures Cloud Movement Over Ligeia Mare

An animated gif of clouds moving across Titan's northern Ligeia Mare (sea). Watch the clouds over the dark area lower center/right. Credit: NASA/JPL-Caltech/SSI

An animated gif of clouds moving across Titan’s northern Ligeia Mare (sea). Watch the clouds over the dark area lower center/right. Credit: NASA/JPL-Caltech/SSI

If you’ve ever been aboard a sailing ship, you probably know the sensation of the craft cutting through the ocean, wind at your back and a breeze in your face. It’s probably the same sensation you get when you go hang-gliding, or water (or snow) skiing.

It turns out, if you lived on Saturn’s icy but intriguing moon  Titan, you could experience the same sensations (provided you could survive the atmosphere and cold temperatures). Of course, your ship would need to be able to withstand the frigid methane sea, and the cold, largely nitrogen (with small amounts of methane and hydrogen) atmosphere.

The clouds would be made of methane, possibly some ammonia, and other hydrocarbons. Feeling the breeze on your face would require you to withstand an atmospheric pressure about 1.5 times that of Earth’s sea level, and near-surface temperatures of about 94 Kelvin (-297 F, or -179 C). Not impossible, but right now, pretty improbable. That’s why we have the Cassini-Solstice Mission — to give us a spacecraft-eye view of what it might look like from above.

So, what would a cloudy, breezy sea day on Titan be like? Cassini scientists just released an animation of clouds blowing across the surface of the northern Titan sea called Ligeia Mare. In the sequence (which you can see here), the clouds blow just over the hydrocarbon-rich sea at speeds of around 7 to 10 miles per hour (3-4.5 meters/second). These images were taken a few weeks ago (late July), and the formation of the clouds and their actions may be harbingers of summer on Titan.

Titan does indeed have seasons during its 30-Earth-year-long year. Each of those seasons lasts about 7 Earth years, giving plenty of time for seasonal change to occur. When Cassini first arrived at Saturn and began studying this moon, its northern pole was pointed away from the Sun, which put it in high winter. At that time, the north polar region was shrouded with a hazy hood. There was a lot of cloud activity in the southern hemisphere (during its summer, when things were a bit warmer (relatively)).

As equinox approached, when both northern and southern hemisphere Titan got equal amounts of light and heat from the Sun, the northern polar hood shrank. Cloud activity continued for a while, until the passing of a large storm in 2010. Then, cloud activity dropped quite a bit. In the approach to northern hemisphere summer (southern hemisphere winter), the northern hood nearly disappeared, and now that we’re starting to see northern summer and southern winter. This latest discovery of clouds above a northern hemisphere ocean could signal summer weather patterns. Their appearance also leads the science team to speculate about whether (or how) the clouds are rela ted in some way to the seas. It’s possible that clouds form over the seas as a matter of course, but it’s also possible that Cassini just happened to catch some clouds racing over the ocean surface as part of a larger-scale circulation pattern.

Cassini will continue studying atmospheric change at Titan during the upcoming northern hemisphere summer (southern hemisphere winter). Already it has given us a great deal of information about the only other world in the solar system (besides earth) that has a fully developed atmosphere (and could possibly be habitable to certain forms of life). Stay tuned!

Worlds in Motion

An animated gif “movie” of Pluto and Charon in motion. This was taken by the New Horizons mission at distance of some 429 to 422 million kilometers (267-262 miles) away. The spacecraft is set to arrive at the Pluto system July 2015.

The New Horizons mission to the outer solar system scored a big one this week with the release of a set of images that clearly — and I DO mean clearly — show Pluto with its largest companion Charon in motion. This is an amazing shot from a huge distance, and the fact that we can “see” the orbital motion of these two places makes them seem somehow more real now. The New Horizons mission has been on the way to Pluto (and beyond) since 2006, with a main goal of imaging and studying the Pluto system, and then sweeping out to see what else it can find in the Kuiper Belt.

I really like what this mission is going to do. Not only is it opening up a dwarf planet for exploration, but it’s going to tell us an incredible amount of cool stuff about the tremendously cold and frigid worlds that exist “out there”. Pluto is on the doorstep of a place in the solar system that likely contains many more worlds of its size and possibly bigger!  This region is a storehouse of materials that exist in pretty much the same chemical state they were in when they formed in the early epochs of solar system history.

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Skygazing is Superlative Enough Without Hyperbole

The Supermoon of March 19, 2011 (on the right) compared with a regular Full Moon of December 20, 2010 that also happened to be in eclipse. This comparison image was created by Marco Langbroek, from his backyard. Found at Wikimedia Commons in a Share and Share-alike license.

No doubt you’ve all seen the hype about the upcoming so-called “Supermoon” on August 10th (Sunday night). And, if you haven’t run into the hype before, you’re probably wondering what all the fuss is about. I always wonder it, too. I’ve tried to see the difference between a regular moon and a Supermoon with  my own eyes. And, either I have really crappy glasses (which I kinda doubt), or I just haven’t seen the difference.  And, I doubt you would either, unless you could somehow magically arrange it so that a regular Full Moon and a Supermoon could appear in the sky at the same time.  Then, you might be able to see the difference in size in how the Moon appears from Earth during one of these events.

Since you can’t do that, you just sort of have to look at the upcoming Supermoon and say, “Hmm… yeah…” and then wonder what all the fuss is about.

So, what’s a Supermoon?  The correct term for the Full Moon we’re about to experience on Sunday is perigee-syzygy of the Earth-Moon-Sun system. The term “Supermoon” is not actually an astronomy term. It’s more of an astrological thing, where soothsayers and people who think the Sun, Moon, and stars are going to tell them when to get rich, who they’re going to marry, and so on, all hang out. It’s really nothing to do with the actual astronomy of the situation.

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