This artist's concept shows NASA's Voyager spacecraft against a backdrop of stars.
This artist's concept shows NASA's Voyager spacecraft against a backdrop of stars. › larger image

Two free public programs in Pasadena next week will present highlights of the scientific bonanza from NASA's twin Voyager spacecraft, launched 25 years ago and still going strong in one of human history's greatest missions of exploration.

Dr. Edward Stone, Voyager project scientist since 1972, will show pictures and explain discoveries from the mission on Thursday evening, Sept. 5, at NASA's Jet Propulsion Laboratory and on Friday evening, Sept. 6, at Pasadena City College.

Voyager 1, launched Sept. 5, 1977, visited Jupiter and Saturn and then angled northward. It is now the most distant human-made object. Voyager 2 also examined Jupiter and Saturn and then became the only spacecraft to visit Uranus and Neptune. Besides those four planets, the twin spacecraft observed 48 moons. They discovered active volcanoes on Jupiter's Io, thick haze on Saturn's Titan, towering cliffs on Uranus' Miranda and geysers on Neptune's frigid Triton.

"Everywhere we went, we found surprises," Stone said. "Over and over we saw that nature is incredibly inventive." The two spacecraft still radio home information almost every day about the outer reaches of the solar wind -- ionized atoms flung outward by the Sun. Scientists hope Voyager 1 will pass beyond the solar wind into true interstellar space before its nuclear power supply runs too low for the spacecraft to tell us about the environment surrounding it, about 20 years from now.

Stone, the David Morrisroe Professor of Physics at the California Institute of Technology, was JPL's director from 1991 to 2001. He has been a principal investigator or co-investigator on 14 NASA missions. Caltech manages JPL for NASA.

Both of his lectures will begin at 7 p.m. Seating is first-come, first-served. The Thursday lecture will be in JPL's von Karman Auditorium. JPL is at 4800 Oak Grove Dr., off the Oak Grove Drive exit of the 210 (Foothill) Freeway. The Friday lecture will be in Pasadena City College's Vosloh Forum, 1570 E. Colorado Blvd. For more information, call (818) 354-0112. Thursday's lecture will be webcast live and available afterwards at