Voyager 2 expected to solve some of Saturn's riddles
(Page 2 of 2)
Another major mystery is Saturn's muted appearance. The gaseous giant Jupiter, by contrast, is a rich riot of color. Unless computer-enhanced, pictures of Saturn's cloudtops are quite bland.Skip to next paragraph
Subscribe Today to the Monitor
Because it is farther from the Sun, Saturn is a cooler plant than Jupiter, and its cloudtops are buried deeper in its atmosphere. One speculation during Voyager 1 was that the planet was obscured by a high-altitude haze which obscured a more Joavian-appearing atmosphere. Preliminary Voyager 2 pictures of the planet show no indication of such a visible haze, however, says Bradford A. Smith, leader of the imaging-science team, which analyzes the photographs sent back by the space probe.
"This strongly suggests that the lack of contrast is something intrinsic to the planet, so the question remains," Dr. Smith says.
Saturn's cloudtops sport a few sports which the scientists feel are quite similar to some on Jupiter. But Saturn lacks the swirling storms that are prominent features on its sister planet, and it has one unique cloud feature which has the meteorologists entranced. This has been dubbed the "No. 6 Cloud," because in one picture it took on a shape vaguely like a "6." This was given joking significance because Saturn is the sixth planet from the Sun."It gives the impression of a corkscrew, spiraling up and filling out," Dr. Smith explains.
Despite its placid appearance, Saturn has one of the most frenetically moving jet streams in the solar system. At the equator the clouds have been clocked at 1,100 miles an hour, four times the speed of the fastest winds on Jupiter.
several of Saturn's 17 moons are also the subjects of extreme interest. Its largest, Titan, is the size of Mercury and is the only satellite in the solar system with a dense atmosphere. Actually Voyager 1 passed by Titan much closer than will Voyager 2. Its pictures showed Titan's atmosphere to be so thick that it was impossible to get even a glimpse of the surface. It strengthened the idea even a glimpse of the surface. It strengthened the idea that Titan's present atmosphere may be similar to that on Earth before life evolved. The flyby confirmed that the moon has a nitrogen-based atmosphere like Earth, with small amounts of methane and hydrogen. No oxygen was detected, as scientists also think was the case early in Earth's history. Activities of the second spacecraft will be limited to trying to detect the strong winds that scientists believe prevail there.
Saturn's other moons were thought to be made mainly of ice, with crater-pocked surfaces. Because they were supposed to contain only small amounts of rocky stuff, experts believed that these satellites had too little radioactive material to melt their interiors -- a process considered necessary to cause geological faults, large rift canyons, and other, similar features. Contrary to the theory, however, several of these moons display faults and canyons. So the second spacecraft will be looking at these features more closely to find any clues to the process by which they were formed.
Saturn also has two unusual satellites which Voyager 2 will photograph closely. One, enceladus, is unusually bright. Scientists expect to find its surface to be extremely smooth and icy.
The other, Iapetus, has a bright and dark face. It has the greatest contrast of any object in the solar system. Roughly one-half of the moon reflects light, about like "dirty snow," while the other is extremely dark, about like asphalt.
"The dirty snow is probably just that," Dr. Smith says. "We don't know what the dark material is." One of the most acceptable theories right now holds that the dark material comes from a dark satellite, Phoebe, which orbits slightly farther out.
A final Saturn mystery involves bursts of radio signals that come regularly from the planet. From Voyager 1 measurements, the scientists have determined that these radio signals originate from one area on the planet and are emitted only when that area is facing the sun.The problem is that the researchers can find nothing exceptional about this region, nothing that would give any indication why it should be an active radio source.