Voyagers 1 and 2

Twenty-five years of Voyagers 1 and 2

In the late summer of 1977, two identical spacecraft (Voyagers 1 and 2) took off
on missions of exploration deep into the outer parts of our solar system. In a departure
from an earlier practice, the spacecraft were not given fanciful names from mythology,
like Mercury or Gemini or Apollo. They were called simply the Voyagers. Both spacecraft
visited Jupiter and Saturn, and Voyager 2 kept going on to Uranus and Neptune. Among
many other things, they discovered that Uranian and Neptunian magnetospheres, both
of them highly inclined and offset from the planets’ rotational axes, suggested
that their sources are significantly different from other magnetospheres.

The Voyagers found twenty-two new satellites: three at Jupiter, three at Saturn,
ten at Uranus, and six at Neptune. Nothing was more surprising than the moon Io,
one of Jupiter’s moons, alive with the most active volcanoes in the solar system,
the only solar system body other than the Earth to be so confirmed. Scientists had
expected a dead, cratered surface like Earth’s moon. Triton, a Neptune moon,
was found to have active geyser-like structures and an atmosphere. Auroral zones
were discovered at Jupiter, Saturn, and Neptune. Jupiter was found to have rings.
Saturn’s rings were found to contain spokes in the B-ring and a braided structure
in the F-ring. Two new rings were discovered at Uranus and Neptune’s rings,
originally thought to be only ring arcs, were found to be complete, albeit composed
of fine material. At Neptune, originally thought to be too cold to support such
atmospheric disturbances, large-scale storms (notably the Great Dark Spot) were
discovered.

Now the wonderous part of the expedition is that both spacecraft are still cruising
on, transmitting data far beyond the Sun’s outermost planets and closer to
the true edge of the solar system, where interstellar space begins. The two one-ton
spacecraft are pulling away from the Sun’s gravitational grip and, will just
keep going on far into interstellar space. As of March 2012, Voyager 1 was 17.9
billion km away from the Sun, and Voyager 2 was 14.7 billion km away from the Sun.
Flight controllers at NASA’s Jet Propulsion Laboratory reported that the Voyagers
show every sign of being able to function long enough for one more significant discovery:
the heliopause, where the solar system ends and the rest of space begins. No one
is sure where that is. The heliosphere extends far beyond the orbit of the outermost
planet (usually Pluto, but sometimes Neptune) to the farthest reach of the sun’s
magnetic field. In all likelihood, scientists say, the heliosphere’s boundary
fluctuates with the varying strength of the solar wind over the eleven-year cycle
of the Sun’s maximum and minimum atmospheric flux.

The successes of the Voyagers were seen in the volume and clarity of the photography
and the steady flow of data on planetary magnetic forces, radiations, and other
phenomena. There were the spectacular vistas of the broad pastel bands circling
Jupiter’s atmosphere, like Easter egg decorations, and the bold storm swirls
in the style of a Van Gough. Ringed Saturn, beautiful from afar, was even more stunning
up close. More thin rings of orbiting debris were discovered and, as hypothesized,
tiny moons were found “shepherding” icy and rocky matter into the rings.
Flying by Neptune, the spacecraft revealed the planet to be a pale blue object glowing
with auroras and crackling from the radio noise of charged particles trapped by
magnetic fields. Icy volcanoes burst through the frozen surfaces of Neptune’s
moon Triton, to the total surprise of scientists. The Voyagers are expected to survive
millions of years of interstellar travel, steadfast as ever; however, they will
do it in silence. Their computers and radios will be dead and the Sun will be receding
into cosmic insignificance, the two spacecraft will have long since lost touch with
their makers and the home on Earth that they left behind in 1977.

Source of Synopsis

Wilford, John Noble. “After 25 years, Voyagers seek solar system’s
end”, The New York Times via International Herald Tribune, Wednesday,
August 14, 2002, pp. 1 and 5.