Today will be the last time we see the surface of Saturn for at least a generation as NASA will crash its 20-year-old Cassini spacecraft into the planet’s surface. The spacecraft will take the final plunge on September 15, at around 7:55am EDT (5:25PM IST), and enter the surface of the planet – a place where no human-made object has ventured before. The end of the mission will be live streamed on NASA TV for the world to see.
Cassini, the $4 billion-plus spacecraft, has provided a trove of information about the planet with rings, aiding significant research in its two decades of existence. However, as the unmanned spacecraft is running out of fuel and the mission has been stretched beyond its intended duration, NASA is left with no choice but to pull down the curtains.
A Vox report explains that keeping Cassini going could potentially risk contaminating one of Saturn’s moons – such as Enceladus or Titan – with microbes from Earth. Enceladus is an ice world that has some ingredients for life, while Titan is a dynamic moon where it rains methane. RELATED: NASA’s Cassini probe makes its final approach to Saturn
However, prior to calling it a day, Cassini is set to conduct one final scientific investigation. As it descends into the surface of Saturn, several instruments of the spacecraft will be on, recording the environment, to determine the composition and chemical compounds.
In its 20 years of lifetime, Cassini has spent 13 years orbiting Saturn, and made several important observations about the surface of Saturn, from discovering new moons around the planet, lakes of methane on Titan, existence of water on Enceladus to making detailed observations about the rings around the planet. However, even as it approaches its end, there are some key mysteries still unresolved.
Cassini has made 22 orbits in and out of Saturn’s region and its rings from the past several months, where the spacecraft measured the mass and age of the rings. However, the inner-ring passes were saved for the grand finale, as the scientists did not know if there would be debris in this space that could have destroyed Cassini. ALSO READ: Google Doodle celebrates NASA’s Cassini Spacecraft entering ‘Grand Finale’ of Saturn Mission
The process of crashing into the surface will itself be quite dramatic. Cassini will make a final pass-by of Titan – Saturn’s moon – which will put it on a collision course with Saturn, and then, there will be no way to stop the spacecraft from crashing. Earl Maize, the project manager of the mission, is quoted as calling this pass, “a kiss goodbye.”
Cassini will turn back to Earth and reconfigure itself to become a makeshift atmospheric probe. While it moves through the empty space, there will be no resistance. However, once it hits the atmosphere, it will begin to tumble, trying to fight to atmosphere. But as Thomas Burk, a NASA Jet Propulsion Lab engineer who has worked on the mission from the beginning, says, “Of course, it will lose that battle.” Once the spacecraft starts to tumble, it will no longer be able to send data back to Earth, and that will spell the end of the mission, as the atmospheric pressure will continue ripping the spacecraft apart. It will then melt, and finally explode.
“The outer surface materials might start to char at first; then you’d see some breaking apart; then when you get down to the metal, once it gets hot enough, it will glow,” says Brett Pugh, a NASA JPL thermal engineer. There’s no oxygen on Saturn, so there’s no fire. But “the propellant tanks will explode eventually as the temperatures get high enough,” he says. The crashing might produce a flash. Although NASA has some telescopes pointed at Saturn’s surface, it is unlikely to record anything.
Cassini was launched from Cape Canaveral in October 1997, in a NASA collaboration with the European Space Agency. It took the spacecraft 7 years to reach Saturn, which is 764 times the size of the Earth. However, as the mission draws to a close, it will perhaps take another Cassini to determine the unresolved questions, such as the exact figure on the mass of Saturn’s rings or their age. ALSO READ: NASA’s Cassini probe to dive into Saturn at 113,000 kms per hour