(_Range to Jupiter, 4.8 million kilometers_). At 5 a.m., at a distance of 71 R_J, Voyager crossed the bow shock for the third time, catching up with the contracting magnetosphere of the planet. About noon, at 66 R_J, the spacecraft finally reached the boundary of the magnetosphere, called the magnetopause. Herbert Bridge, the plasma instrument Principal Investigator, noted that the solar wind pressure as monitored by Voyager 2, still between the Sun and Jupiter, had been for several days from two to five times greater than its level during the Pioneer 10 and 11 encounters. Presumably, this high pressure was the cause of the compressed state of the magnetosphere. However, in the previous few hours the solar pressure had dropped, so Bridge anticipated that the Jovian magnetosphere might soon inflate and expand outward. [Illustration: The southern hemisphere of Jupiter presents a tremendous diversity of atmospheric structure and motion. The Great Red Spot rotates counterclockwise in about six days; above and below it high-speed jet streams flow to the right and the left, while a complex, dynamic cloud pattern develops in its wake. This picture was taken on February 25, when Voyager 1 was 9 million kilometers from the planet. [P-21151C]] Fred Scarf intrigued the press with a tape of the sounds made by high-energy protons coming upstream from Jupiter. The plasma wave instrument had recorded the noise of the protons, mixed with the noise of the spacecraft itself, producing sound effects that sounded somewhat like a mixture of singing whales, a Nor’easter, and the Daytona 500. At the press briefing, interest in the imaging results began to shift from Jupiter toward the satellites. Pictures of each of the four big Galilean moons revealed bright and dark features as small as about 200 kilometers across. Unfortunately, this resolution is not enough to be diagnostic—the spots cannot be interpreted in terms of recognizable geological features, such as mountains or craters. Today one could only speculate, but tomorrow or the next day the answers would begin to come in. Deputy Imaging Team Leader Larry Soderblom conveyed his excitement through a metaphor that would be repeated many times during the next week: “We’re beginning a stage in this mission which represents, I think, one of the most exciting points in man’s scientific exploration of the solar system—in the next few days, we’ll explore four new worlds,” seeing in a few days’ time what it took us centuries to learn about other worlds in our solar system. In terms of our experience with the exploration of Mars, “it is about 1700 AD this morning, tomorrow it will be about 1800, and it will be about 1976 [the year of Viking] by Tuesday evening.” Friday, March 2.