Cassini’s Grand Finale is almost here, but the hardy spacecraft has one more task before it begins a harrowing series of dives between Saturn’s upper atmosphere and its rings.

On Saturday, Cassini will cruise 608 miles above the surface of Saturn’s largest moon Titan for the last time. This last close flyby gives scientists a final opportunity to gather a bunch of science of Titan. The spacecraft will also use Titan’s gravity to tweak its trajectory slightly in anticipation of the Grand Finale.

This small trajectory change seals Cassini’s fate. Mission controllers could leave the spacecraft completely alone after Saturday; it would still slam into Saturn’s atmosphere in September.

One last ride by Titan

It’s going to be a busy weekend for the folks managing Cassini. Not only will the flyby incorporate a pivotal trajectory change, but there’s also a ton of science to collect. Cassini’s radar instrument will get the longest observation of Titan’s methane lakes and seas ever.

The observations could help answer the mystery of Titan’s “magic island?” Ok, so they’re not really islands. In 2013, radar images revealed bright regions in Ligeia Mare (the second largest liquid body on Titan’s surface). A few theories are floating around.

Waves are one possible answer. Bubbles are another and that one is gaining traction this week. A mix of methane and ethane could create bubbles at the surface. The radar imaging system picks it up and produces an image that looks more like a chunk of land.

Here’s an image of Ligeia Mare without the “magic islands.”

Titan no islands

And another showing the bright spot extending beyond the top edge of land.

Titan islands

Saturday’s observation will be the best chance at resolving this mystery. Waves? Bubbles? We shall see.

Cassini’s radar instrument will also take its first crack at studying how deep Titan’s smaller lakes are and their composition.

The Ion and Neutral Mass Spectrometer (INMS) will tackle how Titan’s uppermost atmosphere changes over time. A Magnetometer will take a look at the northern portion of Titan’s magnetic tail.

Fun fact: Titan doesn’t produce a magnetic field by itself. But it does have a magnetotail thanks to the moon’s ionosphere interaction with Saturn’s magnetosphere.

Cassini’s visible light camera will also be busy snapping pictures of Titan at mid-southern latitudes.

The Grand Finale

Saturday’s flyby puts Cassini on course for a region of space no spacecraft has ever traveled before. Between Saturn’s upper atmosphere and its rings. Get ready for some of the most stunning pictures captured during the entire mission.

22. That’s how many times Cassini will soar between the rings and Saturn’s atmosphere. Once about every seven days. And the spacecraft will keep beaming data back to Earth until its final moments on September 15. Cassini will pierce Saturn’s upper atmosphere and burn up. Ending a mission that launched on an October night in 1997.



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