All These Worlds Are Yours by Jon Willis

Author:Jon Willis
Language: eng
Format: epub
Publisher: Yale University Press
Published: 2016-07-03T16:00:00+00:00

Down, Down, Down to Business

Galileo carried with it a descent probe designed to separate from the main spacecraft and make a supersonic plunge into the unknown depths of the Jovian atmosphere. The probe separated from Galileo in July 1995, and on December 7 began its descent phase. Atmospheric entry was staggeringly fast—47 kilometers per second (roughly, 169,000 kilometers per hour)—and the frictional deceleration experienced by the probe was utterly uncompromising: subjected to 230 g of deceleration,2 the probe slowed from its impact speed to subsonic in only two minutes. Just over half of the 150-kilogram heat shield was vaporized in the fiery descent.

At this point, the descent mission nearly ended in disaster. The craft was supposed to deploy a parachute, which would slow the probe to a more stately 160 kilometers per hour and allow for more detailed atmospheric measurements to be recorded. But the parachute did not open on time, deploying one agonizing minute later than planned. By rights the parachute should have failed to function completely: an accelerometer controlling the parachute deployment had been installed backward, and exactly what did allow the parachute to deploy remains a mystery. On the parachute’s opening, the probe descended 156 kilometers into Jupiter’s atmosphere, rewarding the mission scientists with just under one hour’s worth of data, which revealed a turbulent, chemically rich, and dynamic world.

The probe eventually succumbed to the rising temperature and pressure of the Jovian interior: first the parachute melted, initiating a long free fall into the depths of the planet. With no solid surface to strike, the components of the probe steadily melted and then vaporized one after the other until the individual atoms ended their mission by mixing with the liquid metallic hydrogen of Jupiter’s core.

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