NASA’s Cassini spacecraft at Saturn nears fiery finale

These days, when one is discussing space missions beyond the immediate vicinity of Earth and the moon, the most-frequently brought up topic is the many plans to go to Mars.

In August 2009, Cassini had the opportunity to view Saturn at equinox, a special time when the Sun sits directly in line with the planet’s rings.

Earlier this morning, Cassini’s onboard computers recalculated themselves to be able to transfer scientific data back to Earth in real-time.

Linda Spilker, the Cassini project scientist, noted that the spacecraft has been running “a marathon of scientific discovery” for 13 years at Saturn. This is another reason the mission scientists decided on Cassini’s particular end-game: The final dive was a dramatic conclusion to this long and scientifically valuable goodbye.

Cassini’s imaging camera will take a last look at the Saturn system on the day before the plunge and will be off during this final descent.

Cassini launched from Cape Canaveral, Florida in 1997, then spent seven years in transit followed by 13 years orbiting Saturn. But “the propellant tanks will explode eventually as the temperatures get high enough”, he says.

“We won’t watch Cassini burn up”.

Mark Perry, an APL planetary scientist, was part of a team that found hydrogen gas-which could potentially provide a chemical energy source for life-pouring into the subsurface ocean of the icy moon Enceladus from hydrothermal vents on the sea floor. But every mission has to have an end, and Cassini’s is imminent.

“Most of what we have in science textbooks about Saturn comes from Cassini“, JPL Director Mike Watkins said to the Washington Post.

In the following seconds Cassini’s on-board computer would have run through its fault protection procedures in a desperate bid to keep the craft in a safe, stable state. After the completion of six months, Huygens got separated from the Cassini. Just a few hours before it entered Saturn’s atmosphere, the mission team made Cassini roll a bit, positioning the vehicle’s instruments toward the planet while pointing its radio antenna at Earth.

Today, in one of the most thrilling moments-and, for the mission’s scientists and engineers, perhaps the saddest-the orbiter Cassini-Huygens plunged toward Saturn at almost 80,000 miles an hour to incinerate itself. Since the spring it had swooped between the innermost ring and the planet itself, Star Wars style, to send back ever more granular data and ever grander photos.

Titan, May 2012. Saturn has 53 confirmed moons; you’re looking at the largest of them. Perhaps Cassini’s biggest revelation was the fact that Enceladus has a global ocean underneath its crust, one that could be habitable.

While there is no guarantee that there is microbial life on any of these moons, there is a chance of contaminating their surface with Earth microbes.

“We didn’t have any choice”, Maize said in an interview shortly before the end of the mission, when asked why the mission ended with a plunge into the atmosphere. “Even though we’ll know that, at Saturn, Cassini has already met its fate, its mission isn’t truly over for us on Earth as long as we’re still receiving its signal”. The ship also found evidence of liquid ethane and methane in Titan’s hydrocarbon lakes and seas, while also analyzing chemicals that form in the moon’s atmosphere and rain down on Titan. For the first time in its mission, the spacecraft flew between the planet and the rings.