Information can, and should, do heroic work. This is a core principle of the Geoversiv mission. As human beings, we explore the universe, because if we do not, our faculties will be dulled, our contributions will be less significant, and our chances of overcoming any given difficulty that much less assured. Achieving maximum-precision science, at 1 billion kilometers from Earth, requires a decades-long day to day devotion that can only be described as heroic.
The Cassini mission was a pathbreaking feat of interplanetary exploration. Yesterday, the world watched live as the last signals from Cassini—one of the most productive instruments in the history of human science and exploration—closed the distance across our solar system, the probe that sent them having already vaporized in Saturn’s dense atmosphere. The historic device is now part of the planet it studied.
What should never be lost, however, is that the Cassini mission was a feat of daring human exploration. Cassini did not reach Saturn, study its moons, its iconic ring system, and the fluid dynamics of its atmosphere, because people put skepticism before daring. They sought to explore, to discover new knowledge, and to build on that knowledge in an active and evolving way.
Cassini is a monument to science and learning, and its discoveries have helped to inform us about planetary physics, and about the physical origins and unique life-sustaining systems of Earth itself.
We must thank the people at Jet Propulsion Lab, and throughout the NASA family, as well as collaborators in the European Space Agency and Italian Space Agency, who made the Cassini-Huygens mission to Saturn possible. We now know, thanks to their ongoing devotion to excellence in the pursuit of knowledge, far more about how planets can anchor complex orbital systems, where the kinetic and chemical underpinnings of life arise.
Titan—the largest of Saturn’s 62 moon, and which is larger than the planet Mercury—is the one moon in our Solar System with a significant atmosphere. The Huygens probe was the first human-made object to land on a world in the outer Solar System. On Titan, Cassini and Huygens discovered water ice mountains and rivers and lakes of liquid methane. A cold world, vastly different from our own, we now know Titan to be a world that could harbor the chemical preconditions for life.
The ice-covered moon Enceladus, where Cassini observed jets of water and gas shooting high into space, is now known to have a sub-surface ocean of liquid water. Cassini was able to confirm the chemical composition of the subsurface, making Enceladus at least the second of Saturn’s moons that could harbor life.
The science done by Cassini and its mission-support team is critical to our understanding of the limits of all planetary science, including exotic fluid dynamics, polar regions, magnetic fields, and how gravitational fields interact in complex planetary systems. The writer Arthur C. Clarke described the importance of the science the Cassini-Huygens joint mission was sent to do, saying: “One day, our survival on Earth may depend on what we discover out there.”
While we mourn and celebrate the transformational scientific achievements of the Cassini probe, we must not forget that it was the hard-work, collaborative culture, evolutionary learning, and hard scientific method of the human team running the mission that made these achievements possible.
On the afternoon of September 11, 2017, Cassini made its “Goodbye Kiss” flyby of Titan, using the large moon’s gravity to assist its orbital shift down toward the upper atmosphere of Saturn, its final destination. Since then, mission specialists have been working to ensure Cassini would be ready for its end-of-life live uplink to Earth.
As the probe approached Saturn’s upper atmosphere, passing over the edge of the planet’s northern polar region, at over 60,000 miles per hour, it was reoriented to point its antenna at Earth, without wavering, until the end. In the last 60 seconds of its life, Cassini would send real-time atmospheric science data from Saturn back to Earth.
Because light—the fastest thing in the universe—moves at a constant speed of 186,000 miles per second, it would take more than 90 minutes for Cassini’s final data signal to reach Earth. Early on Friday morning, the probe broke up in the intense heat and friction of Saturn’s upper atmosphere, its parts vaporizing to become part of the planet.
The fiery end was always planned, to ensure Cassini would not contaminate any of Saturn’s potentially life-harboring moons. Scientists who had worked on different stages of the Cassini-Huygens mission gathered, to witness, celebrate, and mourn the end of Cassini’s historic mission, together.
The following NASA infographic traces Cassini’s 13-year exploration of Saturn’s moons and ring-system, starting in 2004, after its 7-year journey to Saturn.
The leading edge of planning and methodology for scientific missions to other worlds is forever changed by what we have learned from Cassini’s journey to Saturn. For all people everywhere, the scope of our learning and knowledge is forever expanded.
Past Geoversiv reporting related to the Cassini mission: