Cassini spacecraft bids farewell
After 18 years of observing the solar system, NASA’s Cassini probe has been plunged suicidally into the gassy depths of Saturn. This led to a surprising outpouring of emotion among nerds who follow space exploration. Many people have spoken of being moved to tears by Cassini’s unusual fate.
Cassini followed a complex path through the Saturnine neighbourhood, photographing satellites longknown and just-discovered. The low-machismo, 21stcentury NASA recognizes a remote possibility of space probes becoming “contaminated” by micro-organisms during flybys of bodies that might be biologically viable. Basically, the agency did not want to leave any risk of giving Enceladus herpes from Titan, or vice versa, or what have you.
This led to a decision to steer Cassini deliberately into the face of Saturn, whose great mass will ensure that the components of the probe — which include about 30 kilograms of plutonium — are incinerated, evaporated, and immersed in the planet’s core like a drop in the ocean. Cassini was not launched with enough fuel to leave the gravitational neighbourhood of Saturn when it was finished with its work. Sending it into a solar orbit — like Snoopy, the ascent stage of the Apollo 10 lunar module, which amateur astronomers are hunting for almost 50 years after it was abandoned — was not an option.
Psychologists know that if you show humans a short film of coloured geometric shapes moving about randomly, they will naturally invent a story about it. “Oh, the triangle is in love with the square, and the hexagon is jealous.” Our tendency to anthropomorphize is naturally much stronger — and is arguably appropriate! — when the object is an actual extension of mankind, taking scientific measurements. We are pretty sure that a machine doesn’t have feelings about reaching a state of exhaustion, after fulfilling its purpose loyally, and colliding with a planet. But the machine is a representation of us.
It is, among other things, a piece of art. Anyone who bought the Lego Saturn V kit this summer knows that. If humanity destroys itself, and its spacefaring objects (perhaps even Snoopy) are found by extraterrestrial cultures, they will be able to infer an incredible amount about us — and not just because some of those probes were explicitly designed to communicate facts about humanity. Humans address the very far future in a collective way, largely through engineering and design: language can only reach so far.
So we mourn, as we would mourn if it were announced that Géricault’s Raft of the Medusa, or the Apollo Belvedere, were to be ceremonially destroyed on a particular date. But in the case of Cassini there is also the prolonged mission, the one-way nature of its trip, and the novel circumstances. Other NASA “flagship” craft were disabled quickly and mercifully by hostile planetary environments — like the Viking landers of the '70s — or are leaving the solar system with a decent chance of outlasting the human species — like Voyager 1 and 2. Cassini was sacrificed, asked to die if you like, for an ethical principle. Nay, an environmental one. What could be more 2017 than that?
To have died photographing Saturn — uncovering bizarre mysteries about its surface, its orbital companions, and its rings — is a noble demise indeed. Saturn has a special place in our species’ history, and not just because its satellites seem, by some chance, to be more interesting and weird overall than those of Jupiter and other giants.
It’s the rings. We take them for granted so much that if you ask a child to draw a planet he will probably produce a ringed, Saturn-like object. But the rings were unknown to antiquity, and their discernment in the early era of telescopes was among the key events that made scientific discovery an intellectually attractive frontier. Telescopes revealed the heavens to be full of unsuspected phenomena, but most of them could be understood with reference to Earth or to astronomical chronicles. When Galileo found mountain-like structures on the Moon, the implications for traditional philosophy were dreadful. But in the end, mountains are not fundamentally difficult for the mind to absorb, given time.
But there was no natural analogue or familiar way for interpreting the rings of Saturn: as telescopes became more powerful they only became more unfathomable and beautiful. Why flat rings, with the inner edge facing the planet? Why the apparent gaps between rings?
It required James Clerk Maxwell — who appeared more than 250 years after Galileo, and who had the kind of mind that shows up about that often — to work out theoretically that the rings could not be continuous solid structures. “When we contemplate the Rings from a purely scientific point of view, they become the most remarkable bodies in the heavens,” Maxwell wrote in 1859. “When we have actually seen that great arch swung over the equator of the planet without any visible connection, we cannot bring our minds to rest.” Surely these last six words still apply, despite Maxwell’s own work of mathematical demythologization: perhaps Cassini should have been named for him instead?