Water, water everywhere

University College London: 11-Jul-2007 13:00 Eastern US Time

Scientists have found water on the planet of another star. This is the first time this key substance for living things has been found on an extrasolar planet.

More than 200 extrasolar planets have been discovered so far. These are planets in orbit around a star, in the same way as our Earth is in orbit around the sun.

Extrasolar planets don't usually have interesting names like Venus or Pluto. This one is called HD 189733b. It orbits a star in the constellation of Vulpecula the Fox. It is 64 light years away from us.

HD 189733b is a "transiting planet". This means it passes in front of its star. As transiting planets do this they absorb light from their star.

Different substances absorb different colours of light. So scientists can study the light that comes through their telescopes and discover what the planet's atmosphere is made of.

The team of scientists who discovered water on HD 189733b was led by Dr Giovanna Tinetti. She is a scientist at the European Space Agency and University College, London. The findings will be published in this week's Nature (July 12).

This is the first time that astronomers have been sure there is water on an extrasolar planet. Unfortunately the water is not lying around in puddles in great lakes and oceans full of alien fish and seabirds. We know this because HD 189733b is very hot indeed. So water there is in the form of water vapour in the atmosphere of the planet.

HD 189733b is far from being habitable, says Dr Tinetti, who recently took up an Aurora Fellowship at UCL. In fact it is quite hostile to life. But the new discovery shows that water might be more common out there than scientists thought.

It also shows something very important for future work, she says. The same method Dr Tinetti and her colleagues used to detect water on HD 189733b "can be used in the future to study more 'life-friendly' environments."

NASA's Spitzer Earth-orbiting telescope was used to make the discovery. The scientists made measurements at a number of key wavelengths. These were in the infrared part of the spectrum. It is light at these wavelengths that water vapour absorbs.

The detection relied on Dr Tinetti's painstaking analysis. It also relied on calculation of very accurate water absorption parameters. Dr Bob Barber and Professor Jonathan Tennyson did this. They are in UCL's Department of Physics & Astronomy.

Dr Barber said: "The absorption parameters were calculated from our Barber-Tennyson list of water vapour spectral lines. This includes over 500 million individual absorption features."

Each of these is like a fingerprint, he added. They provide "vital clues to the amount of water present and the temperature of the atmosphere."

Parts of the atmosphere of HD 189733b are very hot - around 2000 degrees Celsius, said Professor Tennyson. He is head of UCL's Physics & Astronomy Department. "You need the millions of lines we calculated to simulate this."

HD 189733 is a star much like our own Sun, although a little cooler. But its planet is very unlike Earth. It is a gas giant like Saturn and Jupiter, the largest planet in our solar system. It is actually 15% bigger than Jupiter.

The main difference between our gas giants and HD 189733b is distance from their parent sun. Jupiter is over five times as far away from the Sun as Earth is. But HD 189733b is more than 30 times closer to its star than Earth is to the Sun. This is why HD 189733b is so much hotter than Jupiter.

The "holy grail" for planet-hunters is to find a planet like Earth that has water in its atmosphere, said Dr Tinetti. "When it happens, that discovery will provide real evidence that planets outside our Solar System might harbour life.

"Finding the existence of water on an extrasolar gas giant is a vital milestone along that road of discovery."

More help with words

electromagnetic waves

feature

identifies

microwaves

model

planet

universe

What's it all about?

1. What have the scientists discovered?
2. What is an extrasolar planet?
3. What is the name of the extrasolar planet that has water on it?
4. How far away from us is this planet?
5. What does a transiting planet do to light from its star?
6. So scientists can study this light to find out which colours are missing. This tells them what substances have -------- the light.
7. Is the water on this planet lying around as a liquid?
8. What form is it in?
9. Could people live on HD 189733b?
10. What phrase from the article gave you the answer to the last question?
11. This discovery does not show there could be life on HD 189733b. But it does show two things. State one of them.
12. Which part of the electromagnetic spectrum were the scientists particularly interested in?
13. In your own words and one sentence explain why.
14. There were two main parts to the work that led to this discovery. One was to collect light from the star using the ------- telescope.
15. Then the scientists had to study this light to see what "colours" or wavelengths it contained - more importantly which ones were missing because they had been absorbed. Was this second part easy or difficult?
16. Which word in the story helped you to answer the last question?
17. Dr Barber mentions two other things about the planet - apart from water vapour being there - that can be learned from the light. What are they?
18. In what way is HD 189733b like Jupiter?
19. In what way is HD 189733b unlike Jupiter?
20. HD 189733 and HD 189733b are names for two different things. Look at where these names are used in the story and explain what each of them means.
21. In one sentence explain why astronomers are so interested in finding water on other planets.
22. If you were these scientists what work would you like to do next?
23. What question would that research be trying to answer?

More activities for this story

Water everywhere UK US

Topic for discussion, research or pupil presentation

A) I chatted to Dr Tinetti about her research earlier this summer, when she first came to London looking for somewhere to live while working at University College. After explaining her approach to searching for life on exoplanets - in which she develops computer models of planetary atmospheres and compares them with observations - she tried to answer a harder question: "Do you think there is life out there on other planets?"

Working in groups, students should listen to the short audio extract of this part of our talk. During the rest of the interview, which lasted over an hour, Dr Tinetti talked confidently about the scientific methods she and her colleagues are using - analysis, modelling, making observations. But in this extract she suddenly starts using a particular phrase that makes her sound very hesitant.

Working in groups students should try to find that phrase, and count the number of times Dr Tinetti uses it or some variant of it. They should then try to decide why the scientist seems so unwilling to be definite when tackling this one question.

The clue, which the teacher might point groups to as necessary, comes right at the end of the recording.

B) More activities:

Teachers' Domain has an appealing set of interactive resources on the search for extraterrestrial life, the Spitzer Space Telescope and infrared astronomy, astronomy at different wavelengths and the importance of water to life. These are pulled together in a comprehensive lesson plan on what makes a habitable planet. A teacher or school needs to register to access this, but this is a simple process from here.

C) Centauri Dreams is probably the best place on the Web for news and informed opinion
on exploring the stars and the prospects of finding life on other planets.

Tips for science class discussions and groupwork

No 55

Science inquiry is typically a collaborative activity and as such involves teams of students in discussing, planning, and conducting investigations together and in sharing responsibilities for talking, reading, writing, and other kinds of presentations. Communication, therefore, plays a major role in science inquiry, and language is one of its central elements. In science inquiry, however, communication involves simultaneous use of other forms such as pictorial and numerical representations. Teams of science inquirers talk about and write their questions, their tentative explanations, their plans, their data, their conclusions, and their reasons and judgements about relationships between evidence and explanations, and about how they make public presentations and scientific arguments in behalf of their work. It is in the context of this kind of scientific activity that students' literacy of the spoken and written word develops along with literacy of the phenomenon. It is also in relation to direct experiences in scientific investigations that words acquire nuances or "negotiated meanings"; inevitably, those meanings differ from meanings conveyed by the same words in ordinary speech.

From Douglas, R. (ed.) et al. (2006) Linking Science & Literacy in the K-9 Classroom. Arlington: NSTA Press.

Ancient green land

Copenhagen University: 5-Jul-2007 14:00 Eastern US Time

The world's oldest DNA has shown that ancient Greenland was once covered in conifer forest and had a mild climate.

Eske Willerslev is an expert in extracting DNA from organisms buried in permafrost. He is a professor at Copenhagen University.

Willerslev has been analysing DNA from beneath Greenland's kilometre-thick icecap. The DNA is close to half a million years old. The results have just been published in the journal Science.

Ten percent of the Earth's surface has been covered with ice for thousands of years, hiding what lies beneath. But scientists have been drilling through the icecap to collect complete columns of ice from top to bottom.

This ice contains yearly layers and is a frozen archive of the world's climate.

Eske Willerslev began to wonder if there might also be DNA buried deeply. If so then perhaps he could reconstruct the living environment of ancient times.

Ice-core samples

The lower parts of the icecap are mixed with mud from the bottom, which is what Willerslev was interested in. So he obtained base layer samples from three drillings. The first two were DYE-3 from the south of Greenland and the GRIP drilling from the middle of the Greenland ice sheet.

The third core came from the John Evans glacier in Canada. This is only a few thousand years old. These samples were used to test the methods.

From the Canada samples Willerslev found DNA from three of the four most common plants that grow in the area. "That means that what one finds under the ice represents the local environment," he explains.

Greenland samples

In the sample from the GRIP drilling, the scientists found no DNA remains at all. Not from plants, mammals or insects. The explanation, says Willerslev, is that the ice in the middle of the ice sheet is over three kilometres thick.

"The greater pressure produces a higher temperature at the base, and so the DNA material, which cannot tolerate warmth, disintegrates."

But at the DYE-3 drilling site the ice is 'only' two kilometres thick. Here the scientists found DNA so well preserved that traces of a long list of plants and insects could be found. These included pine, spruce, alder and yew trees.

There were also remains of flies, butterflies and moths that once flew and fluttered among the Greenland woodland. Traces of beetles and spiders were also found.

These results prove for the first time that there were forests full of life in south Greenland

The genetic material is telling a story of a living environment completely different from what we see today, says Willerslev. "We have found grain, pine, yew and alder. These correspond to the landscapes we find in Eastern Canada and in the Swedish forests today."

The scientists can also tell what the climate was like at the time. This is because each tree species has its own temperature needs. "The yew trees reveal that the temperature during the winter could not have been lower than minus 17 degrees Celsius," says Willerslev

Traces of other trees show that the summer temperatures were at least 10 degrees Celsius.

Dating

The scientists used the genetic traces of butterflies, moths, flies and beetles, to analyse their mitochondria. These contain small pieces of DNA that change with time in a regular way. This means they can be used like a clock to date the DNA.

The team also analysed the insects' amino acids, which also change over time. Both dating methods suggest that the insects were at least 450,000 years old.

The dating of the samples remains uncertain. But the DNA has been preserved under ice for at least 130,000 years, and perhaps up to 1 million years, say the scientists.

More help with words

average

breed

cell

conception

fertile

fertilisation

genes

individual

inherit

molecule

permanent

sperm

subsoil

temperature

What's it all about?

1. Scientists have discovered that something once covered Greenland. What was that?
2. What have the scientists found out about the climate there?
3. What is special about the DNA they used to make these new discoveries?
4. How thick is Greenland's icecap?
5. How old is the DNA the scientists have found beneath the icecap?
6. What have scientists been doing to collect complete columns of ice?
7. Each year more snow falls, so each year a new layer is laid down on the icecap. What does the writer of the article call these layers?
8. The scientists studied samples from how many different drilling sites?
9. Where were these sites?
10. The Canada samples were used to test that DNA from drillings was actually DNA from the ----- environment.
11. The two sets of Greenland drillings gave very different results. What were they?
12. What reason do the scientists suggest for the result at the GRIP drilling site?
13. State six of the living things the scientists found traces of at the third drilling site.
14. What do these results prove for the first time?
15. The results are telling a story of a living ----------- on Greenland much different from the solid icecap that exists there today.
16. What else can the scientists tell about Greenland at the time the trees were alive?
17. In one sentence how can they do that?
18. When were the insects the scientists found traces of actually alive?
19. Willerslev wondered if there was ancient DNA under the ice. If there was he could use it to "reconstruct the living environment" of long ago. In one sentence and your own words what does "reconstruct the living environment" mean?
20. Find a sentence in the story that says what the aim of this work was.
21. Find a sentence or phrase in the story that is a hypothesis.
22. Find a sentence or phrase in the story that is evidence for a hypothesis.
23. If you were these scientists what question would you still have about any of this?
24. Can you think how you might try to answer that question?

More activities for this story

Ancient green land UK US

Topic for discussion, research or pupil presentations

A) In the popular film Ice Age the intrepid heroes meet a whole army of dodos, the flightless bird that went extinct in the 17th century (not during the Ice Age at all but who’s counting?).

These are portrayed as hilariously stupid, headstrong and clumsy birds, which manage to extinguish themselves at every opportunity by crashing into each other, falling off cliffs into diving into molten lava.

While this makes for entertaining episodes, it is very unfair on the poor old dodo and totally misrepresents why species do go extinct. For a start any animal as suicidally stupid as the dodos in this film wouldn’t have evolved and survived in the first place.

In Ice Age 2, Manny the mammoth believes himself to be the last of his kind - until he meets a female mammoth who thinks she’s a possum (don’t ask - you need to see it).

Working in groups, students should choose a bird or animal that is now extinct, such as the dodo, mammoth, sabre-toothed tiger, and explore the various possible reasons for their extinction. They should deliver a presentation on the subject to the class.

The class should then try to find the feature common to all extinctions.

B) An interesting twist on the above is an in-depth lesson from Discovery School, with extension activities and recommended websites. This lesson looks at why particular species, known as living fossils, have survived into the present, when their contemporaries have long gone the way of 99.9% of all species that ever walked, crawled, swam or flew. Extinction is normal.

A nice aspect of the lesson is the following activity that aims to make the scientific method explicit in kids’ minds:

Before beginning the research, have students develop a hypothesis about why their animal did not become extinct. They should write their hypothesis on Part A of the sheet ... Students should base their hypotheses on the facts discussed during step 5, as well as the discussion about why dinosaurs became extinct. Below is a sample hypothesis explaining why coyotes might survive if conditions on Earth changed dramatically and other species were killed off.

Tips for science class discussions and groupwork


No 54

Many of our students are poor readers ... if they do not understand what they read, then school and reading simply become a source of frustration. I am teaching and coordinating our summer school program, which is primarily web based (LA and Math).

There is a ton of reading that these kids must do and many of them simply cannot do it - which is probably much of the reason they are in summer school to begin with. Being able to work one on one with these students has been an eye opening experience. This new perspective, coupled with
what I am learning from the reading course [the Florida On line Reading Professional Development], is causing me to become passionate about the belief that we all (teachers) must accept the responsibility of helping all students become better readers, regardless of our particular content. Many of the students I have been working with this summer are also some of our biggest discipline problems, which may result from the overwhelming frustration they encounter every day.

Extract from an online forum of the National Science Teachers Association by Tina Annucci, Gamble Rogers Middle School, St Augustine, FL

Giant fossil penguins

Giant prehistoric penguins in Peru? It sounds more like something out of Hollywood than real science.

But a researcher from North Carolina State University, along with colleagues in other countries, has shown that two new penguin species reached equatorial regions tens of millions of years earlier than was thought possible. What's more, this was when the earth was much warmer than it is now.

Palaeontologist Dr. Julia Clarke is assistant professor of marine, earth and atmospheric sciences at NC State. She and her colleagues studied two newly discovered extinct species of penguins. Palaeontologists from Peru had found the new penguins' sites in 2005.

Both new species lived on the south coast of Peru. The first is called Icadyptes salasi. These penguins stood 5 feet tall and lived about 36 million years ago. The second new species, Perudyptes devriesi, lived about 42 million years ago. It was roughly the same size as a living King Penguin (2.5-3 feet tall). It represents a very early stage of penguin evolution.

These new penguin fossils are among the most complete yet recovered. They call into question earlier hypotheses about penguin evolution and how penguin species moved from one part of the world to another.

Scientists believed that penguins evolved in Antarctica and New Zealand. They later moved closer to the equator. This was thought to have happened about 10 million years ago - after the Earth had gone through a period of cooling (34 million years ago).

Nowadays we think of penguins as adapted to life in cold countries, Clarke says. "But the new fossils date back to one of the warmest periods in the last 65 million years of Earth's history. The evidence indicates that penguins reached low latitude regions more than 30 million years prior to our previous estimates."

These new species are the first fossils to show that penguins were already living near the equator when the Earth's climate changed dramatically. This happened when the extremely warm Palaeocene and Eocene epochs gave way to "icehouse" Earth and permanent polar icecaps.

Penguins reached equatorial regions during this earlier warm period, these new fossils show. They also thrived there at that time: More species are now known from the new Peruvian sites than live there today.

Clarke and her colleagues estimate that the two Peruvian species are the result of two different dispersal events. They reached this conclusion by comparing evolutionary relationships with the places other fossil penguins have been found.

This showed that the ancestors of Perudyptes seem to have lived in Antarctica. Those of Icadyptes may have started out near New Zealand, say the scientists.

The new penguin specimens are among the most complete yet discovered that show what early penguins looked like. Both have long narrow pointed beaks. This is thought to be an ancestral beak shape for all penguins.

Perudyptes devriesi has a slightly longer beak than some living penguins. But the giant Icadyptes salasi has a much longer beak, with features not known in any extinct or living species.

The beak is sharply pointed, almost spear-like. The bird's neck is robustly built with strong muscle attachment sites. Icadyptes salasi is among the largest species of penguin yet found.

These fossils seem to contradict some of what we thought we knew about the relationship between penguins and climate. But Clarke warns against jumping to conclusions.

We should not assume that because prehistoric penguins were not adapted to the cold, living penguins won't be affected by climate change.

"These Peruvian species are early branches off the penguin family tree, that are comparatively distant cousins of living penguins," Clarke says. "In addition, current global warming is occurring on a significantly shorter timescale.

"The data from these new fossil species cannot be used to argue that warming wouldn't negatively impact living penguins."

More help with words

breed

environment

evolution

fertile

fossil

individual

permanent

placental

species

tentative

tissue

typical

What's it all about?

1. Where have these penguin fossils been found?
2. How many new species have been found there?
3. Who has been studying them?
4. Who found the sites?
5. How tall was Icadyptes?
6. How long ago did it live in Peru?
7. How tall was Perudyptes?
8. Fossils are often simply small pieces of bone or faint impressions in rock. Are these new penguin fossils like that?
9. What word in the story gave you the answer to the last question?
10. These new fossils are forcing scientists to think again about what happened to penguins in the past. What five-word phrase does the writer use to say this?
11. Before this new discovery scientists thought penguins had first appeared on Earth how many millions of years ago?
12. In what countries did they think penguins had first appeared?
13. Were those countries warm or cold at that time?
14. So penguins were thought to always have been birds suited to life in ---- countries.
15. Does this new evidence support that belief or show it was wrong?
16. Climate is just average weather over a long time. So what was the climate like when these penguins were living near the equator?
17. What happened to Earth's climate a long time after the penguins were living in Peru?
18. So was it warmer or colder near the equator, when these penguins lived there, than it is now?
19. Did the penguins do well living near the equator?
20. What word in the story gives you the answer to the last question?
21. "Comparing evolutionary relationships" means studying fossils and different parts of fossils to figure out which ones came first. What did this work suggest to the scientists?
22. Are they sure about this?
23. Find three words in the story that help give you the answer to question. Look in the paragraph that begins "Clarke and her colleagues ..." and in the next paragraph.
24. Depending on your answer to question 15 complete one of these sentences: 1) These new fossils support the belief that penguins have always been suited to life in cold countries because ... Or 2) These new fossils show scientists were wrong to think penguins have always been suited to life in cold countries. The reason is ....
25. With as much detail as you can find, from the whole story, describe Icadyptes salasi.
26. The sentence that begins "We should not assume that ..." is a hard one to make sense of. In your own words what is this sentence trying to say?
27. The very last sentence is also hard to follow. Rewrite this sentence in your own words.
28. What two reasons does Clarke give for making her last statement?
29. If you were these scientists what research would you like to do next?
30. What question would that research be trying to answer?

Topic for discussion, research or pupil presentations

A) In the popular film Ice Age the intrepid heroes meet a whole army of dodos, the flightless bird that went extinct in the 17th century (not during the Ice Age at all but who's counting?).

These are portrayed as hilariously stupid, headstrong and clumsy birds, which manage to extinguish themselves at every opportunity by crashing into each other, falling off cliffs into diving into molten lava.

While this makes for entertaining episodes, it is very unfair on the poor old dodo and totally misrepresents why species do go extinct. For a start any animal as suicidally stupid as the dodos in this film wouldn't have evolved and survived in the first place.

In Ice Age 2, Manny the mammoth believes himself to be the last of his kind - until he meets a female mammoth who thinks she's a possum (don't ask - you need to watch it).

Working in groups, students should choose a bird or animal that is now extinct, such as the dodo, mammoth, sabre-toothed tiger, and explore the various possible reasons for their extinction. They should deliver a presentation on the subject to the class.

The class should then try to find the feature common to all extinctions.

B) An interesting twist on the above is an in-depth lesson from Discovery School, with extension activities and recommended websites. This lesson looks at why particular species, known as living fossils, have survived into the present, when their contemporaries have long gone the way of 99.9% of all species that ever walked, crawled, swam or flew. Extinction is normal.

A nice aspect of the lesson is the following activity that aims to make the scientific method explicit in kids' minds:

Before beginning the research, have students develop a hypothesis about why their animal did not become extinct. They should write their hypothesis on Part A of the sheet ... Students should base their hypotheses on the facts discussed during step 5, as well as the discussion about why dinosaurs became extinct. Below is a sample hypothesis explaining why coyotes might survive if conditions on Earth changed dramatically and other species were killed off.

Tips for science class discussions and groupwork

No 54

Many of our students are poor readers ... if they do not understand what they read, then school and reading simply become a source of frustration. I am teaching and coordinating our summer school program, which is primarily web based (LA and Math).

There is a ton of reading that these kids must do and many of them simply cannot do it - which is probably much of the reason they are in summer school to begin with. Being able to work one on one with these students has been an eye opening experience. This new perspective, coupled with what I am learning from the reading course [the Florida On line Reading Professional Development], is causing me to become passionate about the belief that we all (teachers) must accept the responsibility of helping all students become better readers, regardless of our particular content. Many of the students I have been working with this summer are also some of our biggest discipline problems, which may result from the overwhelming frustration they encounter every day.

Extract from an online forum of the National Science Teachers Association by Tina Annucci, Gamble Rogers Middle School, St Augustine, FL

Bone-crunching wolves

University of California, Los Angeles: 21-Jun-2007 12:00 Eastern US Time

The icy expanses of Alaska were once the home of large, bone-crunching wolves. This was a unique type of wolf that died out, along with many other big animals, at the end of the Pleistocene.

These extinct Alaskan wolves had robust bodies, strong jaws and massive canine teeth. They regularly killed prey larger than themselves and ate their bones, according to research in today's online edition of Current Biology.

These results are surprising, says Blaire Van Valkenburgh of the University of California, Los Angeles. "The unique attributes of Alaskan Pleistocene wolves had not been previously recognised. They show that wolves suffered an extinction at the end of the Pleistocene."

This new research shows that if wolves had not survived in the Old World, there might not be any wolves in North America today.

"But the living gray wolf differs dramatically from that which roamed Alaska just 12,000 years ago."

The gray wolf is one of a few large predators that survived the mass extinction of the late Pleistocene. But this research shows that wolves did disappear at that time from northern North America

To study Alaska's ancient wolves, the researchers collected the remains of bones from the permafrost in eastern Beringia. They examined their chemistry and genes.

Remarkably they found that these late-Pleistocene wolves were distinct from modern wolves. They had different genes and different bodies.

None of the ancient wolves had exactly the same genes as modern wolves, the researchers report. Their skull shape and the way their teeth had worn down showed they were specialised hunters and scavengers. Chemical analysis of the wolf bones confirmed this.

The wolves fed on extinct megafauna, like the bison, mammoth and woodland muskox.

The ancient wolves had large teeth, broad skulls and short snouts, says Van Valkenburgh. This gave them very strong bites. Their teeth were often worn-down or broken. This strongly suggests "regular and frequent bone-cracking and bone-crunching behaviour."

All this came in very handy in ancient Alaska. Wolves there faced stiff competition for food from other fierce competitors. These included lions, short-faced bears and sabre-tooth cats.

When food is scarce modern wolves eat more of their prey, including the bones. They also eat faster which makes broken teeth more likely.

The extinction of this specialised wolf could be a sign of things to come for today's specialised predators, Van Valkenburgh says.

One example is a North American gray wolf that was discovered only recently. It is unusual because it is nomadic. Packs of these wolves migrate with the caribou across the North American tundra. All other wolves have their own territories and do not migrate.

"Global warming threatens to eliminate the tundra, and it is likely that this will mean the extinction of this important predator," says Van Valkenburgh.

More help with words

average

breed

cell

compounds

conception

elements

environment

fertile

fertilisation

herbivore

inherit

permanently

Pleistocene

species

sperm

subsoil

temperature

What's it all about?

1. Where in the world did these wolves live?
2. Is this type of wolf still alive today?
3. What happened to them?
4. Which one word near the start of the story tells what happened to them?
5. How often did these Alaskan wolves kill prey larger than themselves?
6. If wolves had not survived in Europe what might have happened in North America?
7. How long ago were these Alaskan wolves alive?
8. What parts of the wolves' bodies did the researchers study to learn about them?
9. These wolves were different from today's wolves in several different ways, the scientists found. State one of them.
10. Three different pieces of evidence showed that the wolves were specialised hunters and scavengers. State two of them.
11. What did the wolves eat?
12. How did the scientists work out that the wolves crunched bones?
13. In your own words what does "stiff competition" mean?
14. In what kind of conditions do modern wolves behave like these ancient wolves?
15. Are most wolves nomadic or territorial?
16. In one sentence what does this mean?
17. In one sentence why can being specialised sometimes be a problem?
18. If the weather or the supply of food changed, would an animal that was specialised be more or less likely to survive?
19. What change do you think happened that made these Alaskan wolves die out?
20. If you were these scientists what research would you like to do now?
21. What question would that research be trying to answer?

Topic for discussion, research or pupil presentations

Discovery School has a nice lesson on Ice Ages and extinctions. Its learning objectives include the following.

Students will:

• understand what causes ice ages;
• learn about plants and animals that lived during the Ice Age;
• understand why certain Ice Age animals became extinct.

Here is an extract:

Tell students that they are going to conduct some research about the Ice Age and the animals that lived during that period. Divide students into five groups. Each group will be working on the three questions listed below... Visit the Web sites provided with each question for essential background information. Brief answers are provided in italics.

...

Question 3. Why did many animals become extinct at the end of the Ice Age? (Although scientists do not know for sure, they suspect the causes are either hunting by people or environmental changes as a result of the warming of Earth. Some researchers think that overhunting by humans eliminated a major species, either the mammoth or the mastodon, which led to more general extinction. Other scientists think that rising temperatures, changing rainfall patterns, and the melting of the glaciers caused many changes to the ecosystem, resulting in the extinction of certain animals.)

...

Have each group share its findings. What have students learned about the relationship between the environment of the Ice Age and the animals that lived then? What is the relationship between the changing environment of the Ice Age and the animals that became extinct?

Have students complete the Take-Home Activity Sheet: Giving a Scientific Opinion. The purpose of the sheet is to see whether students can apply what they have learned about the Ice Age to modern times. If possible, have students share their ideas with their classmates.

(Note however that some of the links from the Discovery webpage no longer work.)

Tips for science class discussions and groupwork

No 53

Collaborative activities seem to provide less information to the teacher about an individual pupil's progress. This may appear to be a serious drawback for any assessment procedure. However, collaborative discussion, debate and argument are immensely valuable in terms of getting pupils to reflect carefully on their own ideas, to take alternative possibilities seriously and in this way to kick start the learning process.

Naylor, S. and Keogh, B. (2007) Active Assessment : thinking, learning and assessment in science. School Science Review, 88(325), pp 73-79

Martian wandering

University of California, Berkeley: 13-Jun-2007 13:00 Eastern US Time

There were once great oceans on Mars, say a team of scientists at the University of California, Berkeley.

A large plain at the planet's north pole looks very like an ocean basin, even from Earth. Images taken by the Viking spacecraft in the 1980s showed two possible ancient shorelines. Each of these was thousands of kilometres long, with features like those found in Earth's coastal regions.

These dried-up shorelines, as they seemed to be, were name Arabia and Deuteronilus. Scientists estimated the dates when they were filled with water at between 2 and 4 billion years ago.

But then in the 1990s Mars Global Surveyor measured the surface of Mars to a resolution of 300 metres. They found that the shorelines vary in height by several kilometres (more than a mile).

They rise and fall like waves, with several thousand kilometres from one peak to the next.

Here on Earth the height of any shoreline is pretty much the same everywhere. So experts began to reject the notion that Mars once had oceans.

But the UC Berkeley scientists have now found an explanation for the undulating Martian shorelines. The north and south poles of Mars have moved by nearly 3,000 kilometres along its surface. This happened within the past 2 or 3 billion years.

Spinning objects bulge at their equator. So this "true polar wander" could have caused the change in height of the shorelines that we now see on Mars, say the scientists.

"When the spin axis moves relative to the surface, the surface deforms," says study co-author Michael Manga. He is UC Berkeley professor of earth and planetary science. "That is recorded in the shoreline."

The paper will appear in this week's issue of Nature. The lead author is Taylor Perron, a former UC Berkeley graduate student, now a postdoctoral fellow at Harvard University.

Perron's calculations show that the response of Mars' elastic crust could create very large elevation differences for features like a shoreline. This is exactly what we see. The Arabia shoreline varies in elevation by about 2.5 kilometres. The Deuteronilus shoreline varies by about 0.7 kilometres.

"This is a beautiful result that Taylor got," says co-author Mark Richards. He is professor of earth and planetary science and dean of mathematical and physical sciences at UC Berkeley.

"The mere fact that you can explain a good fraction of the information about the shorelines with such a simple model is just amazing. It's something I never would have guessed at the outset.

"This really confirms that there was an ocean on Mars."

So now the question is: What caused Mars' spin axis to move?

A spinning planet is most stable when its mass is farthest from its spin axis. So any shift of mass on the planet could cause the spin axis to move. This might be a shift of mass within the mantle. It could be a mass shift between the mantle and the crust to form a volcano. It could even be an addition of mass caused by a meteorite hitting the planet.

Richards has modelled polar wander in Earth's past. This was generated by the upwelling of hot mantle. Some scientists believe this shifted Earth's spin axis 800 million years ago, by 90 degrees, tipping the planet on its side.

The UC team calculates that on Mars an initial shift of 50 degrees from today's pole would have been enough to disrupt the Arabia shoreline. This is equal to about 3,000 kilometres on the surface.

A shift of 20 degrees from today's pole, or 700 kilometres, would have changed the Deuteronilus shoreline.

Interestingly, today's pole and the two ancient poles lie in a line that is a constant distance from the planet's largest feature. This is the Tharsis rise, a huge bulge near the equator which contains Mars' most recent volcanic vent, Olympus Mons.

Tharsis is the largest volcano in the solar system. It formed about 4 billion years ago, not long after Mars solidified.

The positions in relation to each other of Tharsis and the path of the poles is exactly what scientists would expect if a mass had shifted that was smaller than the Tharsis rise. This is because the planet would then rotate so that the large mass of Tharsis stayed on the equator - as far away from the axis as possible.

"This alignment is unlikely to occur by coincidence," the team writes.

Manga has a hunch about the mass shift that led to the tilt of Mars' spin axis. If a flood of water had filled the Arabia ocean 3 billion years ago, to a depth of several kilometres, that might have been enough to shift it 50 degrees to the south.

When the water disappeared, the pole could have shifted back again. Then it could have shifted again by 20 degrees during the flood that created the Deuteronilus shoreline.

The unknown source of water must have produced a flood greater than any seen on Earth, Manga says. Huge canyons have been cut in the flanks of the Tharsis rise. Where has the water gone?

Well it might have evaporated. But there is another, more intriguing possibility. All that water might have sunk into underground dikes. These would be frozen near the surface.

But they could be liquid below.

More help with words

conference

core

depression

doctorate

erupt

journal

lava

orbit

planet

vapour

research

volcanic

What's it all about?

1. What is the main conclusion of this latest research?
2. Whereabouts on Mars is the large plain that looks like an ocean basin?
3. Roughly how long are the two possible shorelines photographed by the Viking spacecraft in the 1980s
4. What names were they given?
5. How old were they estimated to be?
6. For a while the plains were thought to be the remains of ancient oceans. Then new images started coming in during the 1990s. Which spacecraft took these images?
7. What kind of information about the surface of Mars did these new images show in much more detail than the Viking images?
8. What did this new information about the surface of Mars show about the edges of the large plains?
9. Shorelines on Earth are pretty much at the same height. So there was no obvious reason for shorelines on Mars to vary in height by as much as several ----------.
10. Scientists therefore began to think these were not ancient ----------.
11. But now the UC scientists have found a way to explain how a shoreline could end up with some parts much ------- than others.
12. It is all about what happens when things spin. What happens to the surface of spinning objects near their equators?
13. But the large plain that looks like an ocean basin is nowhere near the equator nowadays. Where is it?
14. For the scientists' new idea to work the large plain must have been much closer to the equator in the past than it is now. In just a few words what makes the equator move? (The article actually talks about the spin axis moving. But if the spin axis moves the equator must move. This is because the equator is an imaginary line around the planet half-way between the ends of the spin axis.)
15. If you stick a lump of wet putty or plasticine onto a spinning ball its spin axis will shift. Exactly the same thing happens if a big rock hits a planet from space. A big rock from space is called a ---------.
16. The spin axis will also shift if big masses of stuff move around the planet – from the inside to the surface or from the surface to its insides. Give one example, which we also see on Earth, of material from inside a planet getting to its surface.
17. So the scientists' idea is that a big mass of something moved on Mars. This made the spin axis shift so that what looks like shoreline was closer to the ------- than it is now.
18. Remember that the surface of a planet ------ near the equator. So parts of the shoreline closer to the equator would have ended up higher than other parts.
19. This is the scientists' idea for explaining why the shoreline is nothing like as level as shorelines here on -----.
20. Manga thinks the moving mass that made the spin axis shift was a flood of water into the ocean. Does he have any evidence for this?
21. Why do you think the possibility that there is liquid water under the surface of Mars is described as intriguing?
22. How sure do you think we can be that things happened just as these scientists say?
23. Make a list of the actual observations that are mentioned in the story, as distinct from ideas, suggestions and the results of calculations.
24. Do you think there might be another explanation for these observations?
25. If you were these scientists what would you like to do next?
26. What would be the aim of that research?

What kind of story is this?
Learning to do science is about learning to think. Experiments, direct teaching, group activities and discussions all have a part to play. So do science news stories.

Like other non-fiction texts, science stories contain different kinds of statements. To get at the science behind the words - and to make reading them an active experience - students should pull a text apart and explore the kinds of statement it contains.

We've met some of these in the later questions of the previous activity. Science news stories usually include the aims of the research or reasons for doing it. They often contain a hypothesis. Sometimes evidence for a hypothesis is given, or a hypothesis is used to make a prediction. Towards the end of a story the direction of future research the scientists are planning is often discussed, as well as outstanding questions the research will be designed to answer.

All these types of statement occur in some science stories. Virtually all science stories, however, will contain statements of the following four types:

• new findings or developments;
• the technology and methods the scientists used;
• previous or accepted knowledge, which may or may not be supported by the new findings;
• issues, implications and applications of the research.

So the next activity is designed to engage students with the latest science news by exploring the meaning and structure of a story as revealed by the content and balance of these four statement types:

Pulling it apart
In groups students should read through the story looking for new findings or developments. Once they have reached agreement, or at least consensus, and have underlined all the statements about what the scientists have just discovered or achieved, they can compare and discuss.

In groups they should go through the story again looking for the technology and methods the scientists used in their research. Once they have reached agreement or consensus, and have underlined the statements that talk about the methods and equipment the scientists used, they can compare and discuss.

They should repeat the activity for existing knowledge.

Any areas of disagreement in these activities - whether among the students or between teacher and students - should be regarded as opportunities for discussion rather than errors to be corrected.

Having fully engaged with the latest science news through the above activities, students will be far better able to talk and think about the science and its implications than someone who has simply read about it in a newspaper or watched a brief item on television.

Now it's time for them to get to grips with the issues raised by the research.

Young people have opinions. But school science traditionally allowed little scope for forming and expressing these - which is why it turned many of them off the subject for life.

Putting it together again

In groups, students should read through the latest story looking for issues, implications and applications. Once they have reached agreement, or at least consensus, and have underlined all the relevant statements in the story, they can compare and discuss.

Having done all this the students are well armed to explore the issues raised by the story. A suggested discussion topic specific to this new story is provided below.

Topic for discussion, research or pupil presentations

A simple demonstration of a spin axis shifting can be done with a football and a lump of something sticky, like wet mud or honey. If the football is set spinning on the floor with its axis straight up, and the sticky stuff dropped in the region of its "north pole" what happens next simulates how the spin axis of Mars has shifted, according to the UC scientists.

Two things to notice, the second not obvious from the story:

1) The sticky stuff ends up going around the equator.

2) It is not the spin axis that shifts, but the planet with respect to the axis. The orientation of the spin axis in space is fixed (apart from the effect of the small torque of the incoming mass), but the positions of the poles on the planet move.

Working in groups pupils should predict what will happen, do the experiment, then compare their predictions with what actually happened. They should then try to explain what they saw.

It takes a bit of teacher practice to get the spin rate and stickiness just right, so that big blobs of honey don't go flying around the room - although this is quite entertaining and isntructive.

A less messy approach would be to use the teaching aid movie on polar wander set up by Dave Stegman at Monash University

Teachers can find more activities, resources and lessons about Mars here

Tips for science class discussions and groupwork

No 52

"The 5-E model is designed to help kids construct their own understanding and then form questions to complete that understanding. Some teachers may find that some items do not lend themselves to the 5-E model, but I have found in my biology class that any subject can be taught with the 5-E model. Where most people turn from the 5-E model is because there is less planning involved and less "classroom confusion" (students may at times be actively moving around the room and creating noise in class). They also feel more in control by being the leader of the classroom instead of being an active part of the learning experience.

For myself, I find it exciting to develop lessons where I get to be creative and I can keep the creativity in my classroom. Personal opinion, but I think that as we move students through to graduation, we are being forced to take the creativity out of their learning experience. The 5-E lets me keep that creativity and excitement level in my class because I am actively involved in the learning. It also lets me use Multiple Intelligences to make learning the information relevant to each student. Sometimes, depending on how the students create their meaning, we are led down different paths than another group of students.

For those that like every class at the same point every day, this can be a hard item to deal with."

NSTA forum entry by teacher Bob Penrose (May 2007)

For more see 5E model and constructivism.