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Science & Space

Huygens to plumb secrets of Saturn moon

By Michael Coren
The Huygens probe parachutes to the surface of Titan in this artist's rendering.
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NASA has high hopes for the Huygens probe.

• Interactive: Huygens descent
• Interactive: Huygens in 3-D
Cassini-Huygens mission to Titan:

  • TITAN: Largest Saturnian moon. May harbor organic compounds similar to those predating life on Earth. Temperature is minus 292 degrees F (180 C).
  • HUYGENS PROBE: Spacecraft is 8.9 feet in diameter and 703 pounds (317 kg). Was released from Cassini on December 24 and enter Titan's atmosphere on January 14.
  • It will take two hours for Huygens to parachute to the surface.
  • After touchdown the probe will sample Titan's atmosphere, measure its wind and rain, listen for alien sounds and, when the clouds part, start taking pictures.

    Source: NASA

    National Aeronautics and Space Administration (NASA)
    Space Exploration
    European Space Agency

    (CNN) -- The Huygens probe will plunge through the orange clouds of Saturn's moon Titan Friday, offering scientists their first glimpse of the mysterious moon.

    "It's going to be the most exotic place we've ever seen," said Candice Hansen, a scientist for the Cassini-Huygens mission. "We've never landed on the surface of an icy satellite. We know from our pictures that there are very different kinds of geological processes."

    If all goes well, the saucer-shaped Huygens will enter the thick atmosphere of Titan Friday at about 5:13 a.m. (ET). The data should start trickling in about five hours later.

    The Cassini-Huygens mission is an unprecedented $3.3-billion effort between NASA, the European Space Agency and Italy's space program to study Saturn and its 33 known moons. The two vehicles were launched together from Florida in 1997.

    "The mission is to explore the entire Saturnian system in considerably greater detail than we have ever been able to do before: the atmosphere, the internal structure, the satellites, the rings, the magnetosphere," said Cassini program manager Bob Mitchell at NASA.

    The Huygens probe, about the size of a Volkswagen-Beetle, has been spinning silently toward Titan since it detached from the Cassini spacecraft on December 24. Cassini will remain in orbit around Saturn until at least July 2008.

    "[The Cassini-Huygens mission] will probably help answer some of the big questions that NASA has in general about origins and where we came from and where life came from," said Mitchell.

    Titan's atmosphere, a murky mix of nitrogen, methane and argon, resembles Earth's before life began more than 3.8 billion years ago. Scientists think the moon may shed light on how life evolved on Earth.

    Finding living organisms, however, is a remote possibility. "It is not out of the question, but it is certainly not the first place I would look," said Hansen. "It's really very cold." A lack of sunlight has put Titan into a deep-freeze. Temperatures hover around -292 F (-180 C) making liquid water scarce and hindering chemical reactions needed for organic life.

    New discoveries

    The mysteries of Saturn, the sixth planet from the sun, have always enticed researchers. Scientists are perplexed why Saturn, a gas-giant composed primarily of hydrogen and helium, releases more energy than it absorbs from faint sunlight. Titan is also the only moon in the solar system to retain a substantial atmosphere, one even thicker than Earth's.

    The 703-pound, battery-powered probe will parachute through Titan's clouds of methane and nitrogen for two and a half hours sampling gases and capturing panoramic pictures. Soon afterward, Huygens will reach the surface. However, its landing site is still a matter of conjecture. Scientists say it could be solid, slushy or even a liquid sea of ethane and hydrocarbons.

    "Those are the kinds of things that we have theories about, but we really don't have data," said Hansen.

    Huygens is expected to hit the upper atmosphere 789 miles (1,270 km) above the moon at a speed of about 13,700 mph (22,000 km/h). A series of three parachutes will slow the craft to just 15 mph (24 km/h). The chutes and special insulation will protect Huygens from temperature swings and violent air currents. Strong winds -- in excess of 311 mph (500 km/h) --will buffet the craft, at times dragging Huygens sideways after its parachute is deployed.

    Sensors will deduce wind speed, atmospheric pressure and the conductivity of Titan's air. Methane clouds and possibly hydrocarbon rain can be analyzed by an onboard gas chromatograph. A microphone will listen for thunder.

    Three rotating cameras will snap panoramic views of the moon capturing up to 1,100 images. A radar altimeter will map Titan's topography and a special lamp will illuminate the probe's landing spot to help determine the surface composition.

    Engineers say they are confident that Huygens and its suite of six sensitive instruments will survive the descent.

    "From an engineering standpoint, I'm very confident in a positive outcome," said Shaun Standley, an ESA systems engineer for Huygens at the Jet Propulsion Laboratory in California. "We've been over this again and again for the last three years fine-tuning this."

    As the largest and most sophisticated interplanetary vehicle ever launched, according to NASA, Cassini-Huygens has performed well on its 2.2-billion mile (3.5 billion km) journey.

    Cassini crossed Saturn's rings without mishap in June 2004 and produced the most revealing photos yet of the rings and massive gas-giant. A problem with the design of an antennae on Cassini almost scrapped Huygens' mission, but engineers altered the spacecrafts' flight plans to resolve the transmission problem.

    Now, Huygens is on its own.

    Controllers can only that hope years of preparation will pay off. "[Huygens] is on its way, we can't contact it," said Standley. "We can't make any changes of anything that is on board. [It's] just waiting for the right moment."

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