2 . From Smells to Soundtracks

When a young sawfly, a bee-like insect, is threatened by its attackers like ants, it emits a mixture of unpleasant smells to defend itself. These emissions can seriously annoy a potential enemy.

Scientists wanting to study these smelly compounds—to understand which aspects of them discourage attackers and why—face great challenges. Meetups between sawflies and ants in a lab are difficult to carry out. There are also a very limited quantity of the insects’ emissions. On the side, Jean-Luc Boevé, a zoologist who studies insects, from the Royal Belgian Institute of Natural Sciences, is an amateur musician and composer. He decided to try a different way—the sound approach. “To be honest, I considered this project so unpractical myself that I set it aside,” he said. It was months before Boevé and his partner, Rudi Giot, finally made a resolution to get started on it.

They chose 16 sawfly species’ emissions to translate into sounds. First, they figured out which molecules (分子) were present in each smelly compound and in what amounts. Then they assigned various characteristics of those molecules matching properties of sound. For example, smaller molecules like a kind of acid found in vinegar, a sour-tasting liquid, evaporate (挥发) quickly, so Boevé and Giot assigned them sounds with higher pitch ( 音 高 ). Larger molecules were given lower-pitched sounds. In all, the scientists created individual audio descriptions for 20 molecules. Then they combined the sounds of each molecule present in a sawfly’s smell to construct the insect’s soundtrack. If a molecule was of higher proportion in an emission, they assigned it a higher volume. In such a case, the smaller a molecule is, the higher its pitch will be; and the higher the proportion of a molecule is, the higher its volume will be.

To test out the audio descriptions they created, Boevé and Giot examined people’s reactions to the soundtracks and compared them to ants’ reactions to the original smells. They played the 16 emission soundtracks and the 20 molecule sounds through speakers to about 50 study participants. Then the scientists measured how far people backed up to get to a “comfortable position” away from the noise. Most of the study volunteers told the researchers that the high pitch, as well as the high volume, was what made them withdraw. “Ants and volunteers moved away from a chemical and its matching soundtrack respectively,” the researchers wrote.

Boevé said he hoped the process would give other zoologists a new way to compare sawflies’ chemical defenses with those from other insects. It may also offer researchers clues about which molecules fight off enemies most.

5 . • What are geysers?

Geysers are types of hot springs which periodically shoot a column of steaming water high into the air. They occur in areas of volcanic activity where hot lava is found close to the Earth’s surface. The name comes from the Icelandic verb geysa, to gush.

• How do geysers work?

Geysers only form under very specific conditions. There must be ample groundwater; an underground heat source; and a ‘plumbing system’ made up of reservoirs and vertical passages or ‘pipes’ through which heated water travels on its way to the Earth’s surface.

Cool water on the Earth’s surface trickles down through porous (多孔渗水的) rock. As it approaches the heat source (hot rocks or a magma chamber) it is heated to extremely high temperatures and starts to rise through a ‘pipe’. The water would usually turn to steam but its depth, plus the weight of cooler water above it, creates what is called a confining pressure that prevents the superheated water from boiling and turning to steam. As the water rises this pressure lessens and steam finally forms and is trapped in' the reservoir. Over time the pressure in the reservoir continues to build until the steam forces the water upwards through the passage to the surface of the Earth, where it erupts through a vent in a spectacular column of steaming water.

• Where are geysers found?

Geysers are rare, with only around 1,000 active worldwide. They occur in the United States (US), Russia, Chile, New Zealand and Iceland. Some erupt almost predictably in cycles of minutes, hours or days, and some have years between eruptions. The tallest active geyser in the world is Steamboat Geyser in Yellowstone National Park (US) which can shoot water more than 90 metres into the air. Unfortunately, it has only done so five times from 2003 to 2013.

Exploring Beyond

Following the call of our restless genes has not ended well for all explorers. The British explorer Captain James Cook died in a fight with Hawaiians ten years after he received the precious map from Tupaia. His death, some say, brought to a close     1    Western historians call the Age of Exploration. Yet it hardly    2    （end）our exploring. We have remained enthusiastic about filling in the Earth's maps; reaching its farthest poles, highest peaks, and deepest trenches（海豹）; sailing to its every corner and then flying off the planet entirely. With the NASA Rover Curiosity now    3    （stir）us all as it explores Mars, some countries and private companies are preparing to send humans to the red planet as well. Some visionaries even talk of having a spacecraft    4    （send）to the nearest star.

NASA's Michael Barratt—a doctor, diver, and jet pilot; a sailor for 40 years; an astronaut for 12—is among those    5    ache to go to Mars. Barratt consciously sees himself as an explorer Cook and Tupaia. "We're doing what     6    did," he says. "It works this way at every point in human history. A society develops an enabling technology,     7    it's the ability to preserve and carry food or build a ship or launch a rocket."

Not all of us    8    ride a rocket or sail the infinite sea. Yet,     9    a species, we're curious enough and interested enough by the prospect to help pay for the trip and cheer at the voyagers return. Yes, we hope to find a better place to live or acquire a larger territory or make a fortune. But we also explore simply    10    （discover）what's there.

We Must Act Now to Protect Our Threatened Oceans

Last week, climate strikers young and old came out in force to call upon the government to act with greater urgency in tackling the global climate emergency.

They     1     very well feel a need to step up their demands upon hearing the awful findings of the special report on the ocean and cryosphere（低温层）in a changing climate, released on Wednesday by the International Panel on Climate Change. The report highlighted the intimate connections which exist between our climate, our oceans and our very existence. It presented irrefutable scientific evidence     2     our warming climate is placing marine and frozen areas of our planet in grave danger, with some changes happening at a much larger scale and faster rate than previously     3    （predict）.

Urgent action is needed     4     we are to keep our planet-and our oceans-safe and habitable. This requires     5    （ambition） targets to reduce our carbon emissions and to shift our energy system away from polluting fossil fuels towards 100% renewable energies Change is also needed in international cooperation around     6     our oceans are protected.

It is hoped that early next year UN member states     7    （sign）a strong global ocean treaty that could pave the way for the creation of marine sanctuaries（禁猎区）.     8    （place）at least 30%of oceans off limits to human activities such as commercial fishing and oil and gas exploration. This is a crucial step towards building the resilience of marine ecosystems and securing a sustainable future for those     9     livelihoods depend on our oceans.

The government has been a vocal champion for ocean conservation. Now is the time for Britain     10    （turn）political will into decisive action by leading the way with the forging of a new global ocean treaty. The prime minster's direct involvement could make the difference between a watered-down agreement or a powerful one