Directions: Fill in each blank with a proper word chosen from the box. Each word can be used only once. Note that there is one more word than you need.

A. wraps       B. poorly       C. generating       D. incomplete       E. sufficient       F. further G. Compressing       H. heats       I. uncertainty       J. pressurize       K. drowned

Neptune Rains Diamonds, and Now We Might Finally Know How

Deep within the hearts of Neptune and Uranus, it could be raining diamonds. Now, scientists have produced new experimental evidence showing how this could be possible.

The hypothesis goes that the intense heat and pressure thousands of kilometres below the surface of these ice giants should split apart hydrocarbon compounds, with the carbon【小题1】 into diamond and sinking even deeper towards the planetary cores.

The new experiment used the SLAC National Accelerator Laboratory’s Linac Coherent Light Source (LCLS)X-ray laser for the most precise measurements yet of how this “diamond rain” process should occur-and found that carbon transitions directly into crystalline diamond.

Neptune and Uranus are the most【小题2】 understood planets in the solar system. They are extremely far—only a single space probe, Voyager 2, has even been close to them, and only for a flyby, not a dedicated long-term mission.

The atmospheres of Neptune and Uranus are primarily made up of hydrogen and helium, with a small amount of methane. Below these atmospheric layers, a superhot, superdense fluid of “icy” materials such as water, methane, and ammonia【小题3】 the planet’s core.

And calculations and experiments dating back decades have shown that, with【小题4】 pressure and temperature, methane can be broken down into diamonds—suggesting that diamonds can form within this hot, dense material.

A previous experiment led by physicist Dominik Kraus used X-ray diffraction to demonstrate it. Now Kraus and his team have taken their research a step【小题5】 . “We now have a very promising new approach based on X-ray scattering,” Kraus said about their latest efforts. “Our experiments are delivering important model parameters where, before, we only had massive【小题6】. The more exoplanets we discover, the more relevant this will become.”

It’s challenging to replicate the interiors of giant planets here on Earth. The first step is to heat and【小题7】 the material to replicate the conditions inside Neptune at a depth of around 10, 000 kilometers: pulses of optical laser are 【小题8】 shockwaves in the polystyrene(聚苯乙烯), which【小题9】 the material up to around 5, 000 kelvin. It also creates intense pressure.

In the previous experiment, X-ray diffraction(衍射)was used to then probe the material. This works well for materials with crystalline structures, but less so with non-crystalline molecules, so the picture was【小题10】 In the new experiment, the team used a different method, measuring how X-rays scattered off electrons in the polystyrene.

This allowed them not just to observe the conversion of carbon into diamond, but also what happens to the rest of the sample-it splits off into hydrogen. And there’s pretty much no leftover carbon.