BellaOnline Forums Education Astronomy The spacecraft that visited other worlds

On October 15, 1997 the Cassini-Huygens mission was launched. It took seven years to journey to the Saturnian system. In order to travel so far the spacecraft needed to use gravity assists, in which flying past a planet gave the craft a certain amount of acceleration. Huygens would land on Saturn's large moon Titan. Cassini is still exploring.

Here is an artist's concept of Cassini's orbit insertion around Saturn.

For more information, see Cassini Mission and Website.

Here's the strange world where Huygens landed. It's Titan, Saturn's planet-sized moon and the most distant body on which a spacecraft has landed.

Globules (probably made of water ice) 10–15 cm in size lie above darker, finer-grained material. Brightening of the upper left side of several rocks suggests solar illumination from that direction, showing a southerly view. A region with a relatively low number of rocks lies between clusters of rocks in the foreground and the background.

Rocks are frozen water on Titan - at extremely low temperatures, they're as hard as the rocks we know on Earth. The sky is an orange color because Titan's hazy atmosphere tends to filter the blue out of the sunlight.

Photo credit: ESA/NASA/JPL/University of Arizona;processed by Andrey Pivovarov

In the 1960s and 70s the Cold War between the USA and the Soviet Union was on. The space race was one of the battle fronts. What could one side do that would show up the opposition?

How about sending a spacecraft to the outer planets? Difficult. It would take thirty years to get to Neptune, and an immense amount of fuel. But what if there were a way around the ordinary limitations, making use of a rare planetary alignment? That's the story of Preparing for the Grand Tour. It eventually led to the two Voyager missions in the late 70s.

Voyager 1 – Gas Giants and a Last Look Homeward

When a rare planetary alignment opened up the outer Solar System, Voyager 1 was sent forth. It observed the gas giants Jupiter and Saturn and their moons. At nearly 4 billion miles from the Sun, on Valentine's Day 1990 the probe turned and took one last picture of home before continuing its journey to the stars. Among the images of the Solar System "Family Portrait" you could just make out Voyager's last view of home, the pixel that contained Earth. Carl Sagan famously christened it the “pale blue dot”

But Voyager 1 has gone on to become The First Starship. It hasn't left the Solar System, but it has passed out of the bubble that the solar wind makes in space. The spacecraft is now in the space between the stars, moving through a plasma made from ancient supernova explosions.

Voyager 2 took the Grand Tour, visiting all four of the gas planets. It's the only space probe that has visited Uranus and Neptune. Voyager 2 is also headed out of the Solar System.