Earth and Space Sciences

Comets: Stories of the Universe

This lesson will investigate how we find out about our universe and objects within it such as comets.

We will look at questions such as:

• What is a comet?

• How are comets different to planets?

• Will a comet collide with Earth?

Engage in the fascinating journey to outer space and how scientists interpret information from probes

This is a print version of an interactive online lesson. To sign up for the real thing or for curriculum details about the lesson go to www.cosmosforschools.com

Introduction: Comets (P1)

Right now, deep in space, a spacecraft called Rosetta that left Earth 10 years ago is rushing to meet a comet. When it does,it will make history as it sends down a landing craft to the surface for the first time.

Comets are made of the dust and ice left over from exploding stars – the very same material that came together to create our solarsystem billions of years ago. In fact, comets are made of some of the bits that were left over.

People have always been fascinated with comets and for a long time they were mysterious – no one knew what they were. Somecome flying in from deep space to appear with their bright tails in the night sky before disappearing, never to be seen again. Otherscome back close to Earth regularly – sometimes taking years to return as they travel millions and millions of kilometers in their hugeorbits around the Sun.

In the olden days, people were scared of them because they thought they brought bad luck. But today scientists say they can tell alot about how our Earth and the other planets were formed. And the scientists guiding Rosetta believe that comets might even holdthe answer to how life began on Earth. They think that the water we now have on Earth - the most essential ingredient for life -might have been put there by a comet that crashed into it long ago.

Of course, no one has ever visited a comet yet, and there's still a lot we don't know about them, which is why Rosetta’s adventure isso exciting. But the scientists will have to be quick. The little landing craft that will touch down on the surface of the comet only hasbatteries to last three weeks.

Read or listen to the full Cosmos magazine article here.

Left: Rosetta mission control team waiting on Rosetta's first signal. Right: Artists impression of our first comet landing,due to happen in November 2014. Image credits: ESA / J. Mai & ESA / ATG media lab.

Question 1

Imagine: In order to preserve its batteries, Rosetta was in a deep sleep for several years as it drifted across space to meet thecomet. However, as it approached the comet, the probe needed to be jolted back to life again. The catch was that there was only aone hour window for this to happen. The scientists at the European Space Agency hadn't heard anything from Rosetta 45 minutesinto the one hour window. Imagine you were one of the scientists in that room, what would have been going through your head atthe 45 minute mark?

Gather: Comets (P1)

Video credit: Head Science / YouTube.

Loading

Question 1

Recall: Comets are primarily composed of

Hint: You may select more than one answer.

rock

dust

craters

ice

liquid water

Question 2

Recall: The long period comets come from a region of spacecalled

Van Allen Cloud

Oort Cloud

Asteroid belt

Kuiper belt

Question 3

Sketch: Below are six different images of a comet, each representing a different distance from the Sun. Draw a blue square aroundthe image representing the comet being furthest from the Sun and a green square around the image representing the comet beingclosest to the Sun. You may optionally add descriptions under each image in white text.

Question 4

Sketch: Label the various parts of the comet below.

Question 5

Describe: Our knowledge about comets has changed over time. Some people used to think that they signalled impending disasterswhile others thought they brought bad luck. Many astronomers today believe that comets may have played an important role in theformation of Earth as we now know it. Describe two key elements of this role.

Question 6

Calculate: Speed is defined as the distance travelled over time. As an equation it is written:

Determine the average speed of the Rosetta probe during its 2.5 year hibernation after having travelled 600 million kilometers.

speed =distance

time

Question 7

Identify: Halley's comet is a short period comet, passing by the Earth every 76 years. Halley's comet was last seen in 1985. In whatyear will the comet next be visible and how old will you be when it is?

Process: Comets (P1)

Video credit: Geobeats / YouTube.

Loading

Question 1

Compare: Use the mind map below to highlight the similarities and differences between the rocky bodies in the Solar System.

Rocky bodies in the Solar System

Comets

Asteroids

Meteors Planets

Question 2

Research: Prior to the Rosetta mission, Professor A'Hearn was involved in another successful comet exploration, that of Giotto.What did Giotto reveal about Halley's comet that surprised scientists? Why was this revelation surprising?

Hint: The original Cosmos Magazine article can help answer this question.

Question 3

Elaborate: Describe the difference between a comet's orbit and the Earth's orbit around the Sun.

Question 4

Argue: Studying comets can be an extremely expensive undertaking. The Rosetta mission alone cost one billion euros. Is spendingthis amount of money on studying comets justified?

Use at least three arguments to justify your position. You may use images and videos to support your writing.

Apply: Comets (P2)

Left: A cross-section of Oort cloud, a giant sphere of material that surrounds the Solar System, which lies right at centreof the illustration. Right: Halley’s Comet. Image credits: SPL Creative / Getty Images & Science Faction / Getty Images.

Video credit: Institute of Physics / YouTube.

Loading

Question 1

Imagine: You are a scientist who has tracked an asteroid that is on a collision course with Earth. Create a campaign to explain theissue to the general public and propose two alternative ways of solving the problem.

To support your campaign, you may wish to include a television ad, a poster, news scripts and more in the project space below.

Career: Comets (P2)

If he were not an astronomer, Michael A’Hearn would have liked to have been the courageous captain of a majestic ship,sailing the high seas and charting new land. But Michael steers a ship on much larger waters.

Credit: University of Maryland

Michael has been involved in a number of pioneering projectsusing space probes like Rosetta to learn more about outerspace. He didn’t always want to be an explorer. In high school,he studied everything but science – including classical Latin andGreek. It was only at university that Michael fell in love withphysics and astronomy.

Michael has dedicated himself to trying to solve the mystery ofwhat the early solar system was like. Comets and asteroids arethe perfect tools to do that, he says. Today, Michael studiescomets the way zoologists study animals in the wild, carefullyobserving them to learn new things about them and theuniverse.

In 2005, Michael captained the Deep Impact mission, the firstmission to look at the insides of a comet to find out what it wasmade of. Michael and his team had to steer a probe the size of acoffee table through space and aim it into the heart of thecomet Tempel 1. The resulting collision between probe andcomet was the first of its kind, and allowed scientists a glimpseinto the composition of one of these ancient nomads of thesolar system.

Outside of work, Michael enjoys sailing his own boat andtravelling to new interesting places.

Question 1

Imagine: The year is 2172 and you are invited to receive a guided tour of the solar system with Professor Michael A'Hearn in anewly invented ultrafast spacecraft. However, the catch is that you can only choose to travel to two parts of the solar system. Wherewould you wish to go and why?

Cosmos Lessons team

Education Editor: Bill CondieArt director: Robyn AdderlyProfile author: Yi-Di NgLesson authors: Paula Mills and Daniel Pikler