NASA’s Cassini mission is nearing its end as the decade-old spacecraft prepares for its final dive into Saturn. The unmanned spacecraft will carry out its ultimate mission of studying more about Saturn closely and analysing the gap between planet’s upper atmosphere and the innermost ring. Plunging the spacecraft was always a consideration and as the spacecraft has almost depleted its fuel resources, the motivation to carry out the final study makes more sense now. Cassini will begin the final spiral towards the ringed-planet on April 22, and by September 15, there won’t be much of the spacecraft left, as it will get shredded by Saturn’s harsh atmosphere.
Launched back on October 15, 1997, the Cassini-Huygens mission was primarily deployed to study Saturn and its satellites. It consisted of two modules including Cassini, the Saturn orbiter, and Huygens, the moon lander for Saturn’s biggest moon Titan. Both the spacecraft entered Saturn’s orbit on July 1, 2004, and after a few months on December 25, 2004, they separated and Huygens landed on Titan on January 14, 2005. Since it has entered Saturn’s orbit, Cassini has earned a lot of achievements to its name. Now, you might wonder why crash the spacecraft rather than letting it float in the emptiness of the outer Solar system? The primary reason for this step is to avoid collision into Titan or Enceladus, both Saturn’s moons which might harbour life. The second factor to this move was the opportunity to study Saturn more closely, especially the uncharted and possibly empty region between the rings and the planet. In this way, we’ll also get to study Saturn’s atmosphere like never before.
The Cassini-Huygens mission made several iconic discoveries and achieved spectacular firsts on its maiden voyage across the Solar system. The entire mission was a joint space mission by NASA, European Space Agency, and the Italian Space Agency. Some of the more spectacular discoveries were: finding out that Titan’s surface had Earth-like features, such as lakes, rivers, seas and even rainfall! The only difference is that on Titan, these are all liquid methane bodies, and not water bodies because Titan’s surface temperature is a freezing minus 179 degrees Celsius. Huygens’ landing on Titan also marked a milestone of being the first probe to land on a body in the outer Solar system. Cassini also went on to discover icy water geysers on Enceladus, one of Saturn’s moons. Further research led to the discovery of a giant ocean of water under the icy surface. This makes Enceladus another prime suspect to support life within the Solar system. You can read more about other discoveries by Cassini in the infographic below.
The beginning of the end
Cassini’s final plunge to death is a new and critical mission in itself. Essentially, every spiral around Saturn will generate some amount of scientific data that can be relayed back to Earth. The orbiter has been doing rounds of the ringed-gas giant since its arrival to conduct research with a safer approach of avoiding ring debris. Because the probe has nearly emptied its fuel, it’s worth the risk to get even closer to the planet.
Travelling at a staggering speed of 122,000 kph (76,000 mph), the spacecraft will complete 22 orbits around Saturn, covering the inner gap of 1,930 kilometers (1,200 miles). Since it’s currently in a different trajectory, Cassini will use Titan’s gravity to slingshot itself into Saturn’s orbit through a gap in the rings. This five-month journey will be essential to a lot of pending studies on Saturn. For starters, we’ll get to know whether the gap is actually empty or there are undiscovered particles orbiting the planet. Saturn’s magnetic and gravitational fields can be closely studied, giving us an idea of what lies beneath the gaseous atmosphere. Due to its close proximity, we’ll receive detailed data for the first time on the composition of the gaseous clouds in its atmosphere using the onboard mass spectrometer. Another mystery that has riddled astronomers and scientists for several years is the hexagonal cloud on the planet’s north pole, something we might be able to demystify after this mission.
The final dive also poses a fatal risk. While travelling at such high speeds, impacts from even small particles might blow up the entire spacecraft. Cassini’s ring-plane crossings will be oriented to shield off the vulnerable instruments behind the high-gain antenna. The team behind this mission are certain that the probability of experiencing a deadly impact is “less than 1 percent”. Additionally, the final dive will be an emotional moment for the team that has worked on the Cassini-Huygens mission throughout its epic journey across the Solar system for more than 19 years.