The Cassini spacecraft had its first close encounter with Saturn's moon Titan Oct. 26. University of Arizona scientists on the mission say Cassini got its first real glimpse of Titan surface geology and digested its first gulp of rich Titan air.
The Oct. 26 flyby was the first of Cassini's 45 close Titan passes over the next four years. Scientists will combine unique types of information from a dozen instruments on the orbiter for new insights on Titan, Saturn's largest and most exotic moon. The NASA spacecraft will deploy the European Space Agency's Huygens probe to Titan in December. The probe, carrying six instruments, will descend through Titan's atmosphere in January 2005.
UA's Cassini scientists are at NASA's Jet Propulsion Laboratory in Pasadena, Calif., for this first close Titan encounter.
Cassini imaging cameras will photograph Titan every 15 minutes or so during approach, said Alfred S. McEwen, a member of the Cassini imaging team, before encounter. Movies of the approach are online at Cassini imaging team home page."We'll get a movie of Titan's very interesting clouds. They form and dissipate and blow in the wind. Some of them are strange shapes and streaks and things we really don't understand.
"Then, as we get closer, we'll start mapping. We'll make a full disk, four-color mosaic. We'll see the surface, we'll see the limb hazes, we'll see whatever clouds there are," McEwen said. "These are things we'll make posters of, and that everyone will have on their walls."
"As we get closer and closer, we map specific regions at higher and higher resolution. This includes a mosaic over the Huygens landing site. It should be our best look at that location," McEwen said.
Cassini cameras will continue snapping high-resolution pictures of different Titan terrains as the spacecraft zoomed on to Titan's night side.
Cassini imaging operations involve an international team of scientists headed by Carolyn Porco, UA adjunct professor of planetary sciences. Porco directs the Cassini Imaging Central Laboratory for Operations (CICLOPS) at the Space Science Institute in Boulder, Colo. Most of the uplink and downlink imaging tasks are handled at the Boulder facility.
"The Titan imaging atmosphere observations for the flyby have been planned by scientists at the Jet Propulsion Laboratory and sequenced in Boulder," Porco said. "But the very close observations, those with the goal of mapping the Titan surface at between 50 and 200 meters per pixel, have all been planned, designed and sequenced by our team members at the Lunar and Planetary Laboratory. It's a very challenging task to plan imaging sequences during a close flyby when the geometry is changing rapidly. And they've done an excellent job. We're in for quite a show."
Robert H. Brown leads Cassini's visual and infrared mapping spectrometer (VIMS) team, based at UA's Lunar and Planetary Lab in Tucson.
"We know VIMS will see through the haze to Titan's surface," Brown said. "At closest approach - 1,200 kilometers (745 miles) - we'll have 600-meter-pixel resolution. We'll be able to see very small geologic features. We'll get very high resolution looks at atmospheric phenomena, too. But from my perspective, the really important thing about this encounter is really digging down below the atmosphere and getting our first real glimpse of Titan geology.
"We don't know what we're going to encounter there. I suppose you can assume we'll see common geologic forms like mountains and craters and tectonic faults, maybe even volcanism," Brown said.
Titan is possibly the land of a thousand hydrocarbon lakes. UA planetary sciences and physics Professor Jonathan I. Lunine theorized as a graduate student more than 20 years ago that Titan could have liquid hydrocarbon seas or lakes. Lunine is the only U.S. scientist selected by the European Space Agency for its 3-member Huygens probe interdisciplinary science team. He and Ralph Lorenz of UA's Lunar and Planetary Laboratory also are members of the radar team. Cassini will get its first radar images of Titan on Tuesday's flyby.
"If either the radar or VIMS system on the orbiter take images of liquid-filled crater basins, that to me would be very, very exciting," Lunine said. Scientists would then have evidence that surface lakes are a source and sink for methane in Titan's hydrologic cycle.
VIMS will see Titan's hydrocarbon pools, if they exist and aren't hidden by some low-lying fog or other strange phenomenon, Brown said.
VIMS team member Caitlin Griffith said, "Closest approach will give us the most exciting VIMS data because we have that clear view down to the surface. We want to isolate different terrain types and start seeing texture.
"When the Cassini spacecraft flew within 339,000 kilometers (210,600 miles) of Titan in July, VIMS was so far away that everything it saw was smeared over 150 kilometers (93 miles)," Griffith said. "That's like taking a picture of Arizona but smearing all of Tucson with all of Phoenix and beyond, towards Flagstaff. This time, we'll be close enough to isolate and identify lakes and mountains, and maybe see shadows cast at different illumination angles."
Cassini won't just look at Titan tonight. Cassini's Ion and Neutral Mass Spectrometer (INMS) will taste mysterious, subtle flavors in Titan's atmosphere, team member and UA planetary sciences Professor Roger Yelle said.
"Our instrument will scoop up a breath of Titan's puffy atmosphere during the flyby," Yelle said. The experiment will measure how many molecules of different masses it got in the gulp of Titan's mostly nitrogen, methane-laced atmosphere.
"Scientists with telescopes have so far seen 19 different chemical molecules in Titan's atmosphere -- more than in any other solar system body's atmosphere except Earth's," Yelle said. Laboratory experiments show there are probably many more kinds of chemicals in Titan's atmosphere, he added.
Yelle and other INMS scientists want to identify the big, complicated and interesting hydrogen-and-carbon-containing molecules because they are part of a planetary system that possibly rains methane and produces ethane ponds.
"Titan is a big laboratory where you get to play with atmospheres on planetary scales," Yelle said.
In addition, Yelle said, he is fascinated by Titan chemistry as a scientist interested in the origins of life.
Learning more about how carbon-containing, or "organic," molecules form doesn't explain how DNA came to be, Yelle said. "A single strand of DNA contains about 3 billion nucleotides that if stretched out, would be something like 1.7 meters long. We're trying to understand molecules with just 10 or 12 atoms."
But Titan's hydrocarbon chemistry holds clues that explain the very first steps of how nature assembled organic molecules, which are the precursors to amino acids, the building blocks of life, he said.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Office of Space Science, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo. The visual and infrared mapping spectrometer team is based at the University of Arizona Lunar and Planetary Laboratory, Tucson, Ariz.
UA Science Contacts on Cassini/Huygens - Scientists from UA's Lunar and Planetary Laboratory (LPL) who work on the Cassini/Huygens mission include:
- Jonathan Lunine, 520-621-2789, e-mail to email@example.com
UA professor of theoretical planetary science and physics, Lunine is an interdisciplinary scientist on the Cassini mission specializing in Titan's surface and atmosphere. He is also a member of both the Radar and the Gas Chromatograph-Mass Spectrometer (GCMS) teams. Lunine began planning the Cassini mission as a graduate student. He titled his feature article on the mission, published in the June 2004 Scientific American, "Saturn at Last!" Lunine is one of the most widely interviewed Cassini scientists when the subject is Titan, Saturn's largest moon. Titan, Lunine says, is "our best chance to study organic chemistry in a planetary environment that has remained lifeless over billions of years. With a thick, nitrogen-rich atmosphere and possibly hydrocarbon seas, Titan may harbor organic compounds important in the chain of chemistry that led to life on Earth."
- Robert H. Brown, 520-626-9045, e-mail to firstname.lastname@example.org
Professor Brown is the leader of the Cassini Visual and Infrared Mapping Spectrometer (VIMS) Science team. The $60 million imaging spectrometer takes pictures in 352 separate colors simultaneously, with wavelengths between 300 and 5100 microns, covering the visible and extending into the infrared. VIMS will identify the chemical make-up and propeties of Saturn's moons. This team determined from the June 11 flyby that Saturn's moon Phoebe came from the outer solar system beyond Neptune. Rick McCloskey (520-626-3255) built VIMS' ground data system, which is the system that controls the experiment and stores all its data. Others on the VIMS grounds operations team headquartered at the Lunar & Planetary Lab are Dan Moynihan, Dyer Lytle and John Ivens. VIMS home page: http://wwwvims.lpl.arizona.edu/
- Caitlin Griffith, 520-626-3806, e-mail to email@example.com
Griffith is a team member on the Visual and Infrared Mapping Spectrometer (VIMS) experiment on the Cassini orbiter, which will image Titan's little known lower atmosphere and surface, and measure the surface composition, cloud morphology and methane humidity. Griffith and her colleagues discovered the presence of methane clouds in Titan's atmosphere, which indicates that Titan has a methane cycle like the hydrologic cycle on Earth, with clouds, rain and seas. Griffith's work also indicates that water ice is exposed on Titan's surface, despite the likely existence of organic sediments and possible methane oceans.
- Ralph Lorenz, 520-621-5585, e-mail to firstname.lastname@example.org
Lorenz is a member of both the Cassini spacecraft's radar mapping team and a co-investigator of the Surface Science Package on the Huygens probe. One of Lorenz' major goals is to map Titan's landscape. He began working on the Huygens project as an engineer for the European Space Agency in 1990, and then earned his doctorate from the University of Kent at Canterbury, England, while building one of the probe's experiments. He joined the University of Arizona in 1994 where he started work on Cassini's Radar investigation. He is a co-author of the book, "Lifting Titan's Veil" published in 2002 by Cambridge University Press.
- Alfred McEwen, 520-621-4573, e-mail to email@example.com
McEwen is member of Cassini's Imaging Science Subsystem (ISS) team and is a planetary geologist and director of the Planetary Image Research Laboratory (PIRL). He also was a member of the imaging science teams of the Galileo mission to Jupiter and is a participating scientist on Mars Global Surveyor (MGS) and Mars Odyssey. He is principal investigator for the High Resolution Imaging Science Experiment (HiRISE) for Mars Reconnaissance Orbiter (MRO) to launch in 2005. For Galileo, McEwen led the sequence planning and science analysis for Jupiter's volcanically active moon Io. For Cassini, he is leading the planning for imaging observations of Saturn's giant satellite Titan. In his cover story, "Journey to Saturn," for the Jan. 2004 issue of Astronomy magazine, McEwen identified 10 top mission highlights. Elizabeth Turtle, Doug Dawson, undergraduate student Jason Perry and graduate student Stephanie Campbell work with McEwen in planning the Titan observations.
- Elizabeth Turtle, 520-621-8284, e-mail to firstname.lastname@example.org
Turtle is part of McEwen's group that planned and will analyze Cassini's imaging observations of Titan's surface. She will use the Cassini images to map Titan's surface and study its landforms. It parallels her work on the Galileo mission to Jupiter, where she mapped and studied landforms, particularly for the moons Io and Europa.
- Roger Yelle, 520-621-6243, e-mail to email@example.com
Yelle is a team member on the Ion and Neutral Mass Spectrometer (INMS) experiment on the Cassini mission. It will analyze the composition of Titan's atmosphere down to the parts per million level. Yelle and his colleagues, including collaborators from the Imperial College London and Boston University, are developing a comprehensive model for the chemistry, energetics and dynamics of Titan's upper atmosphere.
- Martin Tomasko, 520-621-6969, email to firstname.lastname@example.org
Tomasko, research professor in planetary atmospheres and radiative transfer, is the principal investigator on the Descent Imager Spectral Radiometer (DISR) on the European Space Agency's Huygens probe. The DISR is the optical package in the probe, which will separate from the orbiter Dec. 24 and cruise down through Titan's atmosphere mid-January 2005. As the probe descends toward Titan's surface, DISR will be take pictures of Titan's atmosphere and surface using three camera lenses pointed at three different angles. One camera looks straight down, one camera points at an angle of almost 45 degrees, and one camera looks almost straight out horizontally. Tomasko and other scientists will create 20 panoramic mosaics from their Titan images. As the probe gets closer to the ground, it will take too long for the cameras to take panoramic pictures, so they'll begin transmitting individual images.
- Bashar Rizk, 520- 621-1160, e-mail to email@example.com.
Rizk is a co-investigator on the DISR instrument. His responsibilities include fitting the 750 or so images the instrument will acquire into a global context in order to derive the Huygens probe's ground track, its attitude history, its descent trajectory and the horizontal and vertical winds blowing on its journey to Titan's surface. Trying to display the downward-looking and very wide-angle field of view of the DISR imagers when fully mosaicked is challenging: The lower hemisphere below the probe from one horizon to nadir to the opposite horizon has led to the routine development and use of several different projections in order to lay what is basically a spherical surface onto a flat piece of paper. Rizk and other team members will develop perspective animation from their imaging to convey look and feel of this alien world. Rizk is also refining a spherical model of Titan's radiative transfer, including polarization, which will be used to refine the knowledge of Titan's aerosols and radiative energy balance when used with other DISR data returned from the Huygens probe.
- Peter Smith, 520-621-2725, e-mail to firstname.lastname@example.org
Smith, an LPL senior research scientist, is a co-investigator on the DISR instrument. He has been involved with the team since 1989 when he helped write the proposal for the building and design of the instrument. He became project manager during the first 4 years of the project monitoring progress at Lockheed Martin Astronautics. Smith has done notable research on Titan, and will be working with surface data sent back from the Huygens probe, comparing it to observations of the surface obtained by the Hubble Space Telescope. He will also analyze the distribution and type of aerosol particles found in Titan's atmosphere. Smith is principal investigator for the $355 million, 2007-2008 Phoenix lander mission to Mars. This NASA Scout mission is the first Mars mission run by a university.
- Lyn Doose, 520-621-2127, e-mail to email@example.com
Doose is a co-investigator on the Descent Imager Spectral Radiometer (DISR) on the Huygens probe. He will study radiative transfer in Titan's atmosphere, looking at where clouds and haze are found in the atmosphere. He also will interpret data to find the heat budget of Titan (looking at how much solar energy is absorbed, and where on Titan it is absorbed), and study the abundance and absorption properties of gases in Titan's atmosphere.
- Donald M. Hunten, 520-621-4002, e-mail to firstname.lastname@example.org
Hunten, Regents' Professor in Earth and planetary atmospheres, is a co-investigator on the gas chomatograph-mass spectrometer (GCMS) on the Huygens probe. The GCMS will measure the atmosphere composition of Titan as the probe descends, and, with luck, after the probe lands. Hunten and other scientists are interested in learning what elements are present in Titan's thick atmosphere.
- Gabriel Tobie, 520-626-0093, e-mail to email@example.com
Tobie is a visiting scholar who has done previous modeling of Titan's surface and interior. He will use data sent back from the Cassini mission to learn more about the evolution of Titan, the surface cryovolcanic activity and the methane cycle.