Clash of the Titans

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Titan descent by Huygens probe leaving Cassini storage, Christmas 2004. Image Credit: JPL/Space Science Institute

Six years ago, then NASA Associate Administrator Wesley Huntress, Jr., stated , "Wherever liquid water and chemical energy are found, there is life. There is no exception." Few opportune years like 2004 have presented astrobiology with as many remarkable vistas and fresh perspectives on this fundamental triad of water, chemical energy and life.

Consider this year’s accomplishments of those dedicated to searching for life in the universe.

Landing on Mars not once, but twice. Then finding evidence for water on opposite sides of the red planet. Picking up what appears to be methane signals in the martian atmosphere, one of the residues that might prove one day to be the product of underground biology. Scientists began to discuss seriously what colonization strategies make sense.

Setting off to explore the even richer atmosphere of the Earth-like moon, Titan. Spiraling into orbital capture around Saturn and photographing its majestic rings.

Flying through the tail of a comet and heading home after collecting the first extraterrestrial samples from such dusty iceballs. Launching the Deep Impact probe to smash into a comet and watch how the dust and ice get kicked up.

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The haze of an atmospheric layer on Saturn’s moon, Titan. Credit: Voyager Project, JPL, NASA

Filling the astronomy catalogs with well over a hundred new planets, including what may prove to be the first visible exoplanet. Finding some nearby candidates that might occupy temperate locations or safely orbit Sun-like stars.

Witnessing the once-per-century passage of our neighboring Venus across the face of the Sun. The MESSENGER probe took off on its decade long tour of the inner solar system to orbit Mercury.

Discovering the largest planetoids beyond Pluto among those outer nurseries where only comets visit.

The editors of Astrobiology Magazine revisit the highlights of the year and where possible point to one of the strongest lineups ever for beginning a new turn of the calendar. Between the marathon still being run by the twin Mars rovers and the expected descent to Saturn’s moon, Titan, next year promises no letdowns.

Number two on the countdown of 2004 highlights was the Cassini mission to Saturn.


At 1.25 billion kilometers (750 million miles) from Earth, after a 7-year journey through the Solar system, the Huygens probe is about to descend from the Cassini orbiter to enter a ballistic trajectory toward Titan, the largest and most mysterious moon of Saturn, in order to dive into its atmosphere on 14 January. The year brought some of the most spectacular images yet of the outer solar system.

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True color and surface infrared images show features resembling clouds and a continental area about the size of Australia Image Credit: NASA/JPL

On Christmas Eve, the probe destined for the Earth-like moon, Titan, successfully detached and headed off to its controlled collision in a few weeks. The spacecraft will be the first man-made object to explore in-situ this unique environment, whose chemistry is assumed to be very similar to that of the early Earth just before life began, 3.8 billion years ago.

The Cassini-Huygens pair, a joint mission conducted by NASA, ESA and the Italian Space Agency (ASI), was launched into space on October 15, 1997. With the help of several gravity assist maneuvers during flybys of Venus, Earth and Jupiter, it took almost 7 years for the spacecraft to reach Saturn.

The Cassini orbiter, carrying Huygens on its flank, entered an orbit around Saturn on 1 July 2004, and began to investigate the ringed planet and its moons for a mission that will last at least four years.

The first distant flyby of Titan took place on July 2-3, 2004. It provided data on Titan’s atmosphere which were confirmed by the data obtained during the first close flyby on October 26, 2004 at an altitude of 1174 km. These data were used to validate the entry conditions of the Huygens probe.

A second close flyby of Titan by Cassini-Huygens at an altitude of 1200 km is scheduled on December 13 and will provide additional data to further validate the entry conditions of the Huygens probe.

Huygens will remain dormant until a few hours before its arrival at Titan on January 14. The entry into the atmosphere is set for 11:15 CET. Huygens is planned to complete its descent in about two hours and 15 minutes, beaming back its science data to the Cassini orbiter for replay to Earth later in the afternoon. If Huygens, which is designed as an atmospheric probe rather than a lander, survives touchdown on the surface, it could deliver up to 2 hours of bonus data before the link with Cassini is lost.

Direct radio signals from Huygens will reach Earth after 67 minutes of interplanetary travel at the speed of light. An experiment has been set up by radio scientists that will use an array of radio telescopes around the Pacific to attempt to detect a faint tone from Huygens. If successful, early detection is not expected before around 11:30 CET.

What Next?

2005
– Mars Reconnaissance Orbiter (MRO) launch, Mars Orbiter to collect high-resolution, 1-meter, images in stereo-view of Mars
– European Venus Express, Venus Orbiter for two-year nominal mapping life [486 days, two Venus year]

2006
New Horizons, Pluto and moon Charon flyby, mapping to outer solar system cometary fields and Kuiper Belt
Dawn, Asteroid Ceres and Vesta rendezvous and orbiter, including investigations of asteroid water and influence on meteors
Kepler, Extrasolar Terrestrial Planet Detection Mission, designed to look for transiting or earth-size planets that eclipse their parent stars [survey 100,000 stars]
Europa Orbiter, planned Orbiter of Jupiters ice-covered moon, Europa, uses a radar sounder to bounce radio waves through the ice
– Japanese SELENE Lunar Orbiter and Lander, to probe the origin and evolution of the moon

2007
– Japanese Planet-C Venus Orbiter, to study the Venusian atmosphere, lightning, and volcanoes.
– Mars Scout mission, final selections August 2003 from four Scouts: SCIM, ARES, MARVEL and Phoenix
– French Mars Remote Sensing Orbiter and four small Netlanders, linked by Italian communications orbiter

2009
BepiColumbo, European Mercury Orbiters and Lander, including Japanese collaborators, lander to operate for one week on surface
Mars 2009, proposed long-range rover to demonstrate hazard avoidance and accurate landing dynamics


Related Web Pages

2003: Year in Review
Solar System Exploration Survey
Stardust
Genesis
Mars Opportunity Rover
Mars Spirit Rover
Mars Express
Mars Methane
New Planets
Saturn Cassini
Venus Occultation
Planet Ten: Beyond Pluto?