Cassini probe closes on Saturn moon

Scientists hope photos, readings can be captured through smog over Titan

October 26, 2004|By John Johnson | John Johnson,LOS ANGELES TIMES

Space scientists hope to get their first close-up view of one of the solar system's most confounding objects tonight as the Cassini spacecraft passes within 745 miles of Saturn's smoggy moon Titan.

Using an array of infrared and radar imaging instruments, Cassini will attempt to peer through methane clouds to glimpse a landscape that has always been shrouded from Earth-based observers.

Scientists have speculated that within Titan's orange haze, gasoline-type substances might fall like rain on a frozen landscape of rock-hard ice and hydrocarbon pools resembling a toxic chocolate sundae.

"Cassini will see Titan as it has never been seen before," said Charles Elachi, director of NASA's Jet Propulsion Laboratory in Pasadena. "We expect the onboard instruments will pierce the moon's dense atmosphere and reveal a whole new world."

The craft also could also function as a time machine, opening a window on Earth's early history. Titan is the only other body in the solar system with a nitrogen atmosphere; its surface chemistry is thought to be similar to Earth's billions of years ago, said Toby Owen, a Cassini scientist from the University of Hawaii.

Titan is too cold - at minus 290 degrees Fahrenheit - for life as we know it to develop. As a result, it is more like a frozen popsicle than the pre-biotic soup of early Earth.

The Cassini spacecraft was launched in 1997. Because of its size, as big as a bus, there was no rocket capable of sending it directly to Saturn, more than 900 million miles from Earth. Instead, the craft swung past Venus, Earth and Jupiter to slingshot itself into the neighborhood of Saturn and its 33 moons, 15 of which have been discovered since Cassini blasted off.

Titan, Saturn's largest moon and the second-largest in the solar system after Jupiter's moon Ganymede, is a primary objective of the $3.2 billion Cassini mission. It is the only moon in the solar system that has so far been found to have an atmosphere of any kind.

That atmosphere is so dense that it has long kept Titan's secrets hidden.

"It has a thick smog layer that makes the problems in the L.A. basin seem trivial," Owen said.

Cassini passed about 200,000 miles from Titan in July. Images revealed tantalizing bright shapes winking through the haze. But it was impossible to tell whether they were lakes, ice sheets or something else.

The current flyby should yield images as much as a hundred times sharper, resolving objects the size of a football field. "We'll be able to see very small geological features," said Robert H. Brown, who leads Cassini's Visual and Infrared Mapping Spectrometer team at the University of Arizona.

Cassini also is equipped with cameras, a composite infrared spectrometer and radar. Another instrument will sample Titan's upper atmosphere, which extends hundreds of miles above the surface. So far, Earth-based telescopes have detected 19 different chemical molecules in Titan's atmosphere.

The Los Angeles Times is a Tribune Publishing newspaper.

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