Teachers now have a unique opportunity to engage students in an up-close study of Saturn and its marvelous rings, thanks to a NASA web site following a first-of-its-kind mission.
Two decades and $3.3 billion in the making, an international exploration of Saturn began in earnest last night when the spacecraft Cassini slipped through a gap in the planet’s shimmering rings and arced into orbit.
After a seven-year, 2.2 billion-mile journey, Cassini fired its engine June 30 to slow down, allowing itself to be captured by Saturn’s gravity. The maneuver kicked off a four-year, 76-orbit tour of the giant planet and some of its 31 known moons, including huge Titan.
|The Cassini spacecraft is making its way through the rings of Saturn. (NASA photo)|
To scientists, Saturn and its rings are a model of the disk of gas and dust that initially surrounded the sun, and they hope the mission offers important clues about how the planets formed.
Shortly after entering orbit, Cassini will act on its best chance to photograph the rings that have entranced astronomers for centuries.
“We’ll never be that close to the rings as immediately after the insertion,” said Charles Elachi, director of NASA’s Jet Propulsion Laboratory (JPL) and team leader for Cassini’s radar instrument.
Previous expeditions to Saturn were brief. There were fly-bys by Pioneer 11 and the Voyager missions from 1979 to 1981.
Cassini, laden with a dozen instruments, also carries a probe named Huygens that will be launched into the murky atmosphere of Titan. The frozen moon intrigues scientists because it might have many of the chemical compounds that existed on Earth before life began.
Named for 17th-century Saturn observers Jean Dominique Cassini and Christiaan Huygens, the joint project of NASA, the European Space Agency, and the Italian Space Agency dates back to proposals made in 1982.
Many of the project’s 260 scientists have spent years just planning the mission, building Cassini at JPL in Pasadena, Calif., and getting the spacecraft out to Saturn.
“We received our letters of acceptance of being team leaders or team members almost 15 years ago,” Elachi noted at a briefing this month. “So as you could imagine, my colleagues have great anticipation.”
Cassini has already been sending data to Earth, including a wealth of information and sharp images from a close flyby of Saturn’s strange, battered old moon Phoebe.
“It’s a great curtain raiser for the Saturn show that’s about to start at the end of the month,” JPL imaging team member Torrence Johnson said.
High-resolution pictures taken by Cassini of Saturn’s largest outer moon suggest the banged-up rock hails from the outer reaches of the solar system, a mission scientist said June 27.
Photographs released June 27 show shiny patches, probably ice, on Phoebe’s surface, which is dotted with overlapping craters. The ice probably was excavated from under the moon’s surface as objects struck Phoebe over the eons.
Phoebe and a few smaller outer moons orbit Saturn in the opposite direction of the planet’s inner moons. “That alone marks it as a body that was probably captured in Saturn’s orbit early in the life of the solar system,” said Carolyn Porco, leader of the Cassini imaging team.
Educators looking to integrate Cassini’s travels into their lesson plans will find a number of useful resources and teaching materials available on NASA’s web site.
Students and teachers will enjoy unprecedented access to the stunning satellite images of Saturn’s atmosphere, its many moons, and the multi-colored rings that surround this giant plant by visiting the mission’s home page (see link below).
Visitors to the site can follow the Cassini space probe as it inserts itself into the planet’s orbit, view never-before-seen images of Titan and Phoebe, and ponder questions that have intrigued the world’s leading scientists for years, such as “How long is the day on Saturn?”
On the main web site, educators and young explorers will find information about Saturn’s history and live updates on the mission and its progress. For K-12 educators, NASA also has prepared a formal program that aims to incorporate mathematics, science, and technology into a series of lessons built around the Cassini mission.
Details of the Cassini-Huygens mission to Saturn and its moon Titan:
SATURN: Planet second in size to Jupiter with a diameter of 74,898 miles. Mean distance from sun is 890 million miles. Has seven rings of ice and rock particles named “A” to “G” with 31 known moons. Visited by Pioneer 11 (1979), Voyager 1 (1980), Voyager 2 (1981).
TITAN: Largest Saturnian moon, bigger than planets Mercury and Pluto. Believed to harbor organic compounds similar to those that predated life on Earth. Has a hazy nitrogen-rich atmosphere with about 6 percent methane, one-and-a-half times thicker than Earth’s, along with possible ethane-methane seas or lakes. Surface temperature is minus 290 degrees Fahrenheit.
CASSINI ORBITER: Launched Oct. 15, 1997. Spacecraft is 22 feet long, 13.1 feet wide, and weighs 12,593 pounds loaded with fuel and Huygens probe. Makes electricity with nuclear power. Will make 76 orbits of Saturn over four years; 52 close encounters with seven moons.
HUYGENS PROBE: Wok-shaped spacecraft is 8.9 feet in diameter and 705 pounds. Will be released from Cassini on Dec. 24 and enter Titan’s atmosphere on Jan. 14. Will provide up to two-and-a-half hours of science observations during descent by parachute and up to 30 minutes of surface observations.
MISSION COST: $3.3 billion, shared by National Aeronautics and Space Administration, European Space Agency, Italian Space Agency.
Educators who visit the Cassini-Huygens mission’s Education page will find lesson plans for students in every grade level. According to NASA’s web site, the program encompasses everything from basic awareness to in-depth investigative projects intended to help students explore and understand the data collected during Cassini’s pioneering mission. All lessons are aligned with National Education Standards. For teachers, the site also includes links to professional development tools, as well as a list of NASA-sponsored educational web sites for use in the classroom.
On a more leisurely level, young explorers are encouraged to visit the mission’s student web page. Here, students will find a series of stories and activities highlighting some of the challenges faced by scientists during the mission. The site also includes directions on how to find Saturn in the night sky, as well as mission-related art projects and special activities for youth-group leaders.
Cassini is 22 feet long, 13.1 feet wide, and weighed nearly 12,600 pounds loaded with fuel and the probe. Too far from the sun to rely on solar panels, it uses nuclear power to provide electricity.
People who worried that an accident could release nuclear material protested Cassini’s Oct. 15, 1997, launch from Cape Canaveral, Fla. There was more concern when Cassini made a 1999 Earth flyby, but all went as planned.
The wok-shaped Huygens probe, developed by the European Space Agency, will be released from Cassini in December and will enter Titan’s atmosphere in January.
Just under 9 feet in diameter and weighing 705 pounds, its six instruments will investigate Titan’s atmosphere and then its surface, if it survives the impact of landing after a two-and-a-half-hour descent by parachute.
It might not find a hard surface, however, and instead splash down into liquid ethane, which would quickly shut down the probe.
The probe will radio data back to Cassini up to a maximum of 30 minutes after touchdown. By then, either its batteries will have failed or Cassini will have passed over Titan’s horizon.
According to Elachi, some scientists believe Titan has a “pre-biotic” environment in which there is organic, or carbon-based, chemistry, but the surface temperature of minus 290 degrees Fahrenheit is inhospitable to life.
“In a sense, it will give us a past picture of our own planet before biology got started,” he said.