This Friday the legendary artifact ends 20 years of work, rushing towards the gas giant as it transmits it to Earth.
“It’s exciting. After twenty years we bid farewell to this veteran probe.” Nicolas Altobelli, principal scientist of the ESA (European Space Agency) Cassini project, does not hide his admiration for a space adventure that is about to conclude. The scientist is one of the hundreds who have participated in this joint mission of NASA, ESA and ASI (the Italian space agency).
This Friday, September 15, Cassini will culminate the last of the twenty-two laps that it has carried out in recent months on the planet by submerging itself in its atmosphere. The imminent lack of fuel has led those responsible for the project to design the baptized as Grand finale, with which the probe will end its mission by disintegrating in the upper layers of Saturn.
“There were rumors about how it could end but the truth is that it is not possible to escape from that system. Saturn’s gravity is enormous, you can’t run from it“, emphasizes EL ESPAÑOL Altobelli from ESAC, the European Center for Space Astronomy in Villanueva de la Cañada (Madrid).
The team’s priority was comply with planetary protection protocols and that the probe did not run out of fuel in space, which could mean that it collided in an uncontrolled way with one of the planet’s moons, such as Titan or Enceladus.
Thanks to Cassini and its Huygens probe – which landed on Titan on January 14, 2005 – we know that these two moons present hydrothermal activity and that could meet the conditions to host certain forms of life.
sixty second goodbye
After receiving the last gravitational pull of Titan last April, Cassini will enter between Saturn and its rings for the last time this Friday, around two in the afternoon Spanish peninsular time (5 a.m. Pacific Time PDT).
At a speed of 30 kilometers per second and with an entry angle of 15 degrees, the probe will be oriented to transmit data to Earth with its antenna for one last minute. “The end of the mission will be the signal loss“, points out Altobelli. We will know that an hour and a quarter after it happens, because it is the time it takes for the frequency to arrive.
The Deep Space Network station that will pick up this signal will be Canberra (Australia). “We won’t know when exactly it disintegrates”, points out the ESA scientist. After a minute struggling to maintain his orientation, experts estimate that heThe probe will disintegrate at about 1,500 kilometers on the considered surface of reference of Saturn –Being a gaseous planet, it does not have a solid surface like the rocky ones–.
During those sixty seconds in which it will try to withstand the intense friction of the Saturnian atmosphere, Cassini will have all its devices turned on to measure parameters that have never been captured from the gas giant.
With the help of its magnetometer, it will analyze the magnetic and gravitational field, which will allow us to learn more about the unknown interior structure of the planet. Its mass spectrometer will collect information about the composition of its atmosphere and, in addition, the probe will measure the mass of the rings to try to find out when they formed.
Two worlds to discover
Designed in the 1980s – following the success of the Voyager missions to the outer planets – Cassini will make history for achieving unprecedented scientific information since it was released on October 15, 1997 in Cape Canaveral (USA). Taking into account that Saturn takes thirty years to make a complete orbit around the Sun, the mission – whose duration has been extended twice – has covered half a cycle of seasons.
Among its milestones, it stands out having entered the rings of Saturn and showing what the dynamics of its particles are like. It has also captured the huge storms of the planet like no probe before.
In 2012, Cassini photographed a hurricane located at the north pole. Scientists calculated that the eye was 2,000 kilometers across – about 20 times larger than the average size of the eye of a hurricane on Earth – and that its winds blew four times as strongly as those on Earth.
But if Cassini and its Huygens probe will make history for something, it will be for having shown us the surprising hydrothermal activity of the moons Titan and Enceladus. “With Huygens, we landed for the first time on an icy moon in the outskirts of the Solar System,” recalls Micheal Küppers, ESA’s Huygens mission scientist.
The small probe showed during its descent to Titan – Saturn’s largest moon – and during the hour that it was able to send data from its surface canals and mountains that were very reminiscent of the terrestrial ones. Analysis of the data and images later captured by Cassini in one of its flybys revealed that there were liquid methane lakes and that the moon presented a meteorological and hydrological cycle, with an ocean inside it.
As to Enceladus –approximately the size of Spain– the probe has shown us columns of water vapour, geysers near the south pole, which indicate the presence of an underground sea of liquid water under its icy surface. Further analysis has revealed the existence of hydrogen gas in the jets and the possibility of hydrothermal activity that could provide a source of chemical energy for life.
New missions to other moons
completed their scientific goalsOnce Cassini plunges into Saturn’s atmosphere and sends back whatever information it can capture one last time, it will take researchers months to process and analyze all the data.
In parallel, new missions aspire to continue his legacy by discovering the secrets of other icy moons, as is the case with the mission JUICE, of the ESA that will study the satellites of Jupiter, or Europa Clipper, from NASA, with the focus on one of these moons, Europe, which could hold an ocean inside.
for now there is no approved project for saturn satellites. “Having a kind of ship or plane on Titan would be very interesting because it is the body most similar to Earth,” says Miguel Pérez Ayúcar, engineer of the ESA Huygens mission. Although he admits the difficulties of being able to observe what is inside the icy crust of the moon, the engineer affirms that it could be accessed through areas where it is thinner.
Until that happens, the data provided by Cassini will continue to reveal gas giant mysteries many years after the probe has disappeared. Even if the mission ends, its trail will remain forever in the rings of Saturn, as the Zombies in one of the anthems of the Madrid scene.