News, Science

Cassini Spacecraft Begins Last Stage Of 20-Year Mission

Saturn. Photograph from Cassini, taken on October 2004. Image: NASA

In October 1997, a spacecraft called the Cassini orbiter was launched on a mission to explore Saturn and its moons.

Now, after nearly 20 years in space, Cassini’s mission is coming to an end. Cassini is running out of fuel. Scientists expect it to burn up in Saturn’s atmosphere in September.

But before that happens, the spacecraft will make a series of dives between Saturn and its rings, sending photographs and other information back to Earth.

Cassini is a joint project of NASA, the European Space Agency (ESA) and the Italian space agency (ASI). It took seven years for the spacecraft to reach Saturn, after travelling about 2.2 billion kilometres. It completed its first orbit of the planet on July 1, 2004. (Cassini was the fourth Earth spacecraft to reach Saturn, and the first to orbit it.)

Scientists have learned many exciting things from the Cassini mission. They used to think Saturn had 17 moons, but now they know there are actually 62 moons orbiting the planet. Cassini also added to scientists’ understanding of storms on Saturn, the ice and dust that make up its rings, and the atmospheres and geography of some of Saturn’s moons. (In 2005, Cassini delivered a space probe to the biggest moon – Titan – so scientists could get a closer look at the moon’s surface.)

One of the most important discoveries Cassini made was that there is warm, liquid water under the ice that covers one of Saturn’s smaller moons, Enceladus. Scientists believe conditions on Enceladus could be similar to the conditions that led to the development of life on Earth.

Cassini’s mission was supposed to end in 2008, but because it was still in good shape and still sending back useful information, scientists extended it to 2017.

Now Cassini is performing the last task of its mission. On April 26, it flew through the narrow gap between Saturn and its innermost ring for the first time. It will pass through that gap 22 times altogether, gathering even more valuable information and images to send back to Earth.

When Cassini runs out of fuel and enters Saturn’s atmosphere in September, it will burn up like a meteor. Scientists say it is necessary for Cassini to be totally destroyed so there is no chance that microbes from Earth could contaminate any possible life on Saturn. But the information Cassini has sent home from Saturn makes it one of the most successful exploration missions ever launched from Earth.

Related Links

More information about the mission.

Facts about Saturn.

How old would you be on other planets? Find out, here.

Watch this excellent video: Cassini’s Grand Finale (3:40)

By Kathleen Tilly

Writing/Discussion Prompt
Before the Cassini orbiter was launched into space, scientists believed that there were 17 moons orbiting Saturn. Thanks to Cassini, they discover that there are actually 62 moons orbiting Saturn. What a surprise!

Have you ever had a situation where you believed one thing and then you found out it wasn’t true? What was the situation? How did you react when the discovery was made and your mind was changed?

Reading Prompt: Demonstrating Understanding
Before you read this article, make a T-chart. On one side of the chart, write down all of the information you know about Saturn. After reading the article, write down all of the information you learned about Saturn on the other side of the T-chart. What new information was the most surprising to you and why? What further questions do you have about Saturn or the Cassini orbiter? How could you find answers to your questions?

Demonstrate understanding of a variety of texts by summarizing important ideas and citing supporting details (OME, Reading: 1.4).

Demonstrate understanding of increasingly complex texts by summarizing important ideas and citing a variety of details that support the main idea (OME, Reading: 1.4).

Language Feature: Possessive nouns
A noun is a person, place or thing. A possessive noun shows ownership. To make a single noun possessive, add an apostrophe and an ‘s’. For example, “The dog’s bowl was empty”.

Find all of the possessive nouns in the article. There is one possessive noun that doesn’t follow this rule. Why do you think this is the case?