More than 30 years after its mission was conceived and 20 years after its launch, the space probe Cassini will plummet early Friday to a planned death — a self-immolation, if you will, as friction from Saturn's atmosphere turns it into a man-made meteor.
Cassini has done its job well, its discoveries too numerous for easy summary. It found water on two of Saturn's moons and organic compounds on one, suggesting the possibility of primitive life forms. It provided scientists with a better understanding of the famous rings around Saturn that were first identified by Galileo. It sampled material that was spraying out in massive plumes from the moon Enceladus, and conducted other tests and measurements that have unlocked some of Saturn's mysteries while uncovering new ones. It also landed a probe on Titan, Saturn's biggest moon, which radioed measurements and readings for more than an hour before Cassini hurtled off beyond its reach. The probe, named Huygen, is the only man-made object to carry out a surface landing in the outer solar system, and it remains on Titan's surface, a silent sentinel amid yellowish sand and stones.
Cassini, of course, is not NASA's only space probe. For half a century, the agency has, often with international partners (the European Space Agency sponsored the Huygen probe), deployed its odd-looking unmanned space vehicles to the sun, to other planets, and to the deep darkness beyond the reach of the sun's gravitational field. They are the mechanical eyes and ears of a curious species whose efforts to understand the universe have gone from making up legends to making actual trips, both in person and by proxy, into the unknown.
Voyager 1, launched 40 years ago, has lasted longer than any of the other probes. It still sends short messages back to Earth from nearly 13 billion miles away — now outside the solar system. As impressive as that is, Cassini, has mesmerized us with its pictures of everything from fissures on the surface of moons invisible from Earth without a telescope, closeups of those famous rings, and ripples of color in Saturn's gaseous surface. In the end, while technology has made the Earth smaller — people on the other side of the world from Los Angeles can read this right now — Cassini has helped make the solar system smaller. We hope that, among its other achievements, it has built confidence in the value of science at a time when that confidence is under attack at the highest levels of government, and that it has whetted the curiosity of mankind for yet more exploration to help answer the most fundamental of questions: How did we come to be?