Weekly Briefs74

The spacecraft Cassini, which has been circulating Saturn and its moons for the last 13 years, will take a deep change in orbit to get closer to the planet in preparation of its final days looking for a decent burial on the surface of Saturn.

Today (4/26/2017) Cassini will move from its present orbit and will approach Titan—the largest moon of Saturn. The enormous gravity of Titan will move Cassini between Saturn and its innermost ring, a narrow gap where no human artifact has ever been. This maneuver will not happen only once. Cassini, as commanded by NASA, will perform this operation 22 times—once a week—until September 15, 2017. After its final visit, NASA will direct Cassini to crash into Saturn so its final resting place will be on the planet where its main work happened: sending extraordinary images of Saturn and its environment to Earth, and for the discoveries of what the scientific world believe to be the place in the solar system that is most likely to harbor life outside Earth.

Cassini-Huygens (it has a second name!) was launched on October 15, 1997, using a powerful Titan 4B rocket. Weighting 5,670 kilograms, its mission was to circle Saturn and to send images and data. It reached Saturn in July 2004 after almost a four-billion kilometer trip. During the 13 years of exploration of this obscure corner of the solar system, Cassini found a promising environment for scientific discoveries that nobody could have predicted without the help of Cassini: among them, the six-sided 20,000-mile storm embracing the planet’s North Pole, the extensive exploration of Titan, the strangest moon in the solar system and the mysterious moon Enceladus—covered with fresh, clean ice, making it the shiniest object in the solar system and the most likely place that could support life. NASA calls Enceladus an “ocean world.”

Cassini made multiple flights very close to Enceladus and discovered water-rich plumes venting from the moon. An analysis of the plumes detected hydrogen, which indicates that hydrothermal activity is taking place in the bottom of the “ocean.” This energy and heat could provide a good environment for the creation of microbes, according to many in the scientific world. Unfortunately for Cassini, the possibility of the existence of microbes in Enceladus and the fact that the spacecraft approached Enceladus many times is one reason NASA wants to incinerate it at the end of its mission. We do not want the microbes attached to Cassini to contaminate the biotic world out there in the neighborhood of Saturn.

Before Cassini, scientists—including Galileo—looking at the Saturn rings through telescopes never guessed what they were looking at. Today is different. Alexandra Alter on April 22, 2017, writes in a front page article of the New York Times “…now we have extended our reach. Nothing Cassini has done or found so far has moved the markets back here on Earth. It moved only our souls, our minds and our imaginations. It made us freer and bigger by showing how little we know and how much more room there is to expand our thoughts and dreams. How little of nature’s repertoire we have even guessed at.

Let’s delight in some of the pictures Cassini sent us.

Saturn in Infrared. Infrared image of Saturn. Credit: NASASaturn in Infrared. Infrared image of Saturn. Credit: NASA

Cassini’s first of 22 crossing between Saturn and its rings. Cassini’s first of 22 crossing between Saturn and its rings.

Cassini passing over Titan. Credit: ReutersCassini passing over Titan. Credit: Reuters

Saturn’s moon Enceladus. Credit: ReutersSaturn’s moon Enceladus. Credit: Reuters

Enceladus close look. Credit: ReutersEnceladus close look. Credit: Reuters

Earth seen from from Cassini. Saturn ring on top. Credit: ReutersEarth seen from from Cassini. Saturn ring on top. Credit: Reuters

Cassini over Saturn. A depiction from NASA. Credit: NASACassini over Saturn. A depiction from NASA. Credit: NASA

Hexagonal storm of Saturn’s North Pole. Credit: ReutersHexagonal storm of Saturn’s North Pole. Credit: Reuters