The table below gives information concerning the planets. Use the reading passage to help you fill in the table. Some of the boxes have been filled in for you.
Write NO MORE THAN THREE WORDS/AND OR A NUMBER from the passage for each answer.
Model Atmosphere Shows Signs of Life
Life could exist on planets that are much farther from their stars than the Earth is from the Sun. Planetary scientists at NASA’s Ames Research Center in California have developed models for climates on other planets that make the existence of life in other solar systems much more likely.
The scientists, James Kasting, Brian Toon and James Pollack, have increased by more than 75 million kilometres the distance an Earth-sized planet may be from a star and yet support life. The atmosphere on such a planet could be unlikely to support human life, but it could support some forms of life, according to the researchers. “We’re saying that these planets may be habitable, but not necessarily inhabited,” Kasting, an atmospheric physicist, told New Scientist.
The models suggest that the concentrations of carbon dioxide in the atmosphere would be enough to warm planets and prevent water from freezing as far away as the orbit of Mars from the Sun — an average distance of 228 million kilometres. The average distance of Earth from the Sun is 150 million kilometres.
In the past, scientists doubted that “civilizations" could exist in other solar systems because the chance of an Earth-like planet evolving is slim. Michael Hart of NASA's Goddard Space Flight Center in Maryland has calculated that if the Earth were 5 per cent closer to the Sun, its oceans would evaporate, or if it were 1 per cent farther away, glaciations would take over. Hart’s work suggests that only a narrow range of orbits — within a few million kilometres either side of the Earth’s orbit of the Sun — would provide a habitable environment in another solar system.
But the scientists at Ames have pushed the range of orbits for Earth-like planets by more than 50 per cent. Habitable planets could be found from 0.95 to 1.5 astronomical units, they say. One astronomical unit (AU) is the distance from the Earth to the Sun. 1.5 AU is about the distance from the Sun to Mars.
The work at Ames might also help to explain what planetary scientists call the “Goldilocks paradox’’. Earth and its two neighbouring planets, Mars and Venus, were formed at the same time, about 4.6 billion years ago, from the same ingredients, including water, carbon dioxide and nitrogen. But only Earth developed life. Mars is too cold. Venus is too hot, but Earth is just right, like Goldilock’s porridge.
The scientists say that earlier models, including Hart’s, failed to include the stabilizing effect of the exchange of carbon dioxide between the atmosphere and the silicate rocks in the Earth’s crust. This exchange helps to regulate atmospheric and surface temperatures. Exchange of C02 also regulated temperatures in the early history of Venus and Mars before Venus became too hot and Mars became too cold.
In its first few hundred million years, Venus may have had a thin atmosphere and hot oceans, like the Earth, that were capable of supporting life. The scientists have developed a new model called “wet greenhouse" to explain how Venus evolved into its current hell-like state where clouds of sulphuric add fill the sky and surface temperatures reach 460C. The model challenges the generally accepted “runaway greenhouse" model that Fred Hoyle first suggested in the 1950s.
According to the "runaway greenhouse", Venus has always had a heavy atmosphere which traps the Sun's heat In primordial times, the atmosphere was a mix of water vapour and C02. The water vapour would have risen to the upper atmosphere, well above the level at which water condenses. Ultraviolet radiation from the magnetically active young Sun would have split the water molecules into hydrogen and oxygen and the hydrogen would have escaped into space. The result would be a dry planet, with no oceans and high concentrations of C02 in the atmosphere.
But, say Hasting and his colleagues, there are two problems with this model. Where is the oxygen stored and why is there no surplus water? Escape of hydrogen from the stratosphere would have ceased when the level of water vapour in the lower atmosphere reached about 20 per cent of saturation. The stratosphere would have become dry but water should have remained in the Venusians atmosphere.
By adding a mechanism to recycle C02 on early Venus as happens today on Earth — the two objections can be met. The water carried by the lumps of rock from which Venus formed could well have condensed out to form oceans with at least and tenth of the volume of those currently on Earth. The oceans were hot, about 100°C but the pressure of the atmosphere would have prevented excessive evaporation.
An exchange of C02 occurred for several hundred million years between the atmosphere and carbonate rocks on the surface of the planet. The process, known as "weathering”, reduced the density of the Venusian atmosphere to about that of the Earth. The thinner atmosphere allowed most of the hydrogen to escape. The remainder escaped more slowly over the next few million years, so that Venus now has about 100,000 times less water than Earth. According to Hasting and his colleagues, the early interaction between the atmosphere and the surface rocks may also have locked up most of the planet’s oxygen.
After the water was gone, exchange of C02 would have ceased and the level of C02 in the atmosphere would have risen causing a severe “greenhouse” effect. Clouds of sulphuric acid would also have evolved. On Mars, according to the model, carbonates were recycled for about a billion years but eventually, the exchange broke down because the planet was too small to retain its internal heat The C02 has become trapped in carbonate rocks. The thin atmosphere caused the planet’s surface to freeze.
List the three elements that were formed on the Earth 4.6 billion years ago.
,
What helps regulate atmospheric exchange and surface temperature is the exchange of CO2 between the atmosphere and in the earth's crust.
The effect of “weathering” on Venus is reducing the density of the atmosphere to about that of the earth.
| Distance from the sun | Effects of distance on planets | Periods of the exchange of co2 occurs | Reason of breakdown of co2 exchange | Surface temperature | |
| Earth | constantly | ************ | ********* | ||
| Mars | in its first | too small to retain its | freezing | ||
| Venus | no infomation given | in its first | was almost gone | degree celsius |
AI explanationShows the answer. Tap to open.
Question Focus: Finding the exact list of elements mentioned in the passage
Correct Answer: water
Why this is correct: The passage lists the ingredients from which Earth was formed 4.6 billion years ago. Water is clearly named as one of these elements, so it must be copied exactly.
Passage Reference: Earth and its two neighbouring planets, Mars and Venus, were formed at the same time, about 4.6 billion years ago, from the same ingredients, including water, carbon dioxide and nitrogen.
Common Mistake: Some students write liquid water or oceans, but those ideas appear later. You must copy the exact word from the list. This is a synonym trap.
Paraphrasing: Passage: 'including water, carbon dioxide and nitrogen' = Question: 'three elements that were formed'
Tips: When a question asks for a list, look for commas in the passage.
Key Vocabulary:
- ingredient = element
Question Focus: Copying the exact item from a list
Correct Answer: carbon dioxide
Passage Reference: Earth and its two neighbouring planets, Mars and Venus, were formed at the same time, about 4.6 billion years ago, from the same ingredients, including water, carbon dioxide and nitrogen.
Why this is correct: The same sentence names carbon dioxide as one of the original elements. The wording must match the passage exactly.
Common Mistake: Writing CO2 is risky unless clearly accepted. Always copy the full words to avoid a format trap.
Paraphrasing: Passage: 'carbon dioxide' = Question: 'elements'
Tips: Prefer full words instead of chemical symbols unless the passage uses the symbol.
Key Vocabulary:
- carbon dioxide = CO2
Question Focus: Completing a list from the passage
Correct Answer: nitrogen
Passage Reference: Earth and its two neighbouring planets, Mars and Venus, were formed at the same time, about 4.6 billion years ago, from the same ingredients, including water, carbon dioxide and nitrogen.
Why this is correct: The third element listed is nitrogen. All three answers come from the same sentence.
Common Mistake: Misspelling the word, for example nitogen, loses marks. This is a spelling trap.
Paraphrasing: Passage: 'nitrogen' = Question: 'elements'
Tips: Double-check spelling when copying scientific words.
Key Vocabulary:
- nitrogen = a gas in air
Question Focus: Identifying what CO2 exchanges with
Correct Answer: silicate rocks
Passage Reference: failed to include the stabilizing effect of the exchange of carbon dioxide between the atmosphere and the silicate rocks in the Earth's crust.
Why this is correct: The passage explains that temperature is regulated by CO2 exchange between the atmosphere and silicate rocks.
Common Mistake: Writing just rocks is incomplete. The type of rocks matters. This is a partial truth trap.
Paraphrasing: Passage: 'exchange of carbon dioxide between the atmosphere and the silicate rocks' = Question: 'exchange of CO2 between the atmosphere and'
Tips: Do not shorten phrases unless the passage does.
Key Vocabulary:
- silicate = mineral-based
Question Focus: Identifying which atmosphere is described
Correct Answer: venusian
Passage Reference: The process, known as "weathering', reduced the density of the Venusian atmosphere to about that of the Earth.
Why this is correct: Weathering reduced the density of the Venusian atmosphere, according to the passage.
Common Mistake: Some students write Venus only, but the adjective form is required. This is a grammar fit trap.
Paraphrasing: Passage: 'Venusian atmosphere' = Question: 'the density of the ___ atmosphere'
Tips: Check whether the gap needs a noun or an adjective.
Key Vocabulary:
- Venusian = related to Venus
Question Focus: Distance of Earth from the Sun
Correct Answer: 1 AU
Passage Reference: The average distance of Earth from the Sun is 150 million kilometres.
Why this is correct: The passage states Earth is 150 million kilometres from the Sun, which equals 1 AU.
Common Mistake: Writing about 150 million adds an extra word and breaks the limit. This is a word limit trap.
Paraphrasing: Passage: '150 million kilometres' = Table: 'Distance from the sun'
Tips: Use numbers exactly as written.
Key Vocabulary:
- astronomical unit = Earth-Sun distance
Question Focus: Effect of distance on Earth
Correct Answer: habitable
Passage Reference: We're saying that these planets may be habitable, but not necessarily inhabited
Why this is correct: Earth is described as being in a zone that allows life, meaning it is habitable.
Common Mistake: Writing inhabited changes the meaning. This is a paraphrase trap.
Paraphrasing: Passage: 'may be habitable' = Table: 'Effects of distance on planets'
Tips: Be careful with similar-looking words.
Key Vocabulary:
- habitable = suitable for life
Question Focus: Distance of Mars from the Sun
Correct Answer: 1.5 AU
Passage Reference: as far away as the orbit of Mars from the Sun - an average distance of 228 million kilometres.
Why this is correct: Mars is said to be 228 million kilometres from the Sun, which equals 1.5 AU.
Common Mistake: Using Earth's distance instead is a context shift trap.
Paraphrasing: Passage: 'orbit of Mars' = Table: 'Mars distance'
Tips: Check you are reading the correct planet.
Key Vocabulary:
- orbit = path around the Sun
Question Focus: Effect of distance on Mars
Correct Answer: too cold
Passage Reference: But only Earth developed life. Mars is too cold.
Why this is correct: The passage directly states Mars is too cold.
Common Mistake: Writing freezing copies from the table, not the passage. This is a wrong source trap.
Paraphrasing: Passage: 'Mars is too cold' = Table: 'Effects of distance'
Tips: Always take wording from the passage, not the table.
Key Vocabulary:
- cold = low temperature
Question Focus: Length of CO2 exchange on Mars
Correct Answer: billion years
Passage Reference: On Mars, according to the model, carbonates were recycled for about a billion year
Why this is correct: CO2 recycling on Mars lasted for a billion years.
Common Mistake: Writing several billion years adds information not stated. This is a qualification trap.
Paraphrasing: Passage: 'for about a billion years' = Table: 'in its first'
Tips: Pay attention to numbers and quantities.
Key Vocabulary:
- billion = 1,000 million
Question Focus: Reason CO2 exchange stopped on Mars
Correct Answer: internal heat
Passage Reference: because the planet was too small to retain its internal hea
Why this is correct: Mars could not keep its internal heat, so the exchange broke down.
Common Mistake: Writing heat alone is incomplete. This is a partial truth trap.
Paraphrasing: Passage: 'retain its internal heat' = Table: 'Reason of breakdown'
Tips: Do not remove key adjectives.
Key Vocabulary:
- retain = keep
Question Focus: Effect of distance on Venus
Correct Answer: too hot
Passage Reference: Mars is too cold. Venus is too hot
Why this is correct: The passage contrasts the planets and clearly says Venus is too hot.
Common Mistake: Writing very hot changes the wording. This is a synonym trap.
Paraphrasing: Passage: 'Venus is too hot' = Table: 'Effects of distance'
Tips: Copy intensity words like 'too' exactly.
Key Vocabulary:
- hot = high temperature
Question Focus: Duration of CO2 exchange on Venus
Correct Answer: several hundred million years
Passage Reference: An exchange of C02 occurred for several hundred million years
Why this is correct: The passage states the exchange lasted several hundred million years on Venus.
Common Mistake: Writing billion years confuses Venus with Mars. This is a context shift trap.
Paraphrasing: Passage: 'several hundred million years' = Table: 'in its first'
Tips: Check which planet the sentence refers to.
Key Vocabulary:
- several = more than a few
Question Focus: What disappeared on Venus
Correct Answer: water
Passage Reference: After the water was gone, exchange of C02 would have ceased and the level
Why this is correct: CO2 exchange stopped after the water was gone.
Common Mistake: Writing oceans is not exact. This is a synonym trap.
Paraphrasing: Passage: 'the water was gone' = Table: '___ was almost gone'
Tips: Short answers are often correct.
Key Vocabulary:
- gone = disappeared
Question Focus: Surface temperature of Venus
Correct Answer: 460
Passage Reference: surface temperatures reach 460C.
Why this is correct: Venus has surface temperatures that reach 460 degrees Celsius.
Common Mistake: Adding degrees exceeds what is written. This is a wording trap.
Paraphrasing: Passage: 'reach 460C' = Table: '___ degree celsius'
Tips: Do not repeat units already given in the table.
Key Vocabulary:
- surface temperature = temperature of the planet
General Tips:
- Summary and table completion questions follow passage order.
- Always copy the exact words from the passage, not synonyms.
- Check grammar clues like adjectives before nouns.
- Watch spelling carefully, especially with scientific terms.
- Keep an eye on the word limit for every gap.
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