In what way did the scientists suppose alien life might be thriving?

admin2021-03-19  31

问题 In what way did the scientists suppose alien life might be thriving?
  
Alien life might be purple. That’s the conclusion of a new research paper that suggests that the first life on Earth might have a lavender hue. In the International Journal of Astrobiology, microbiologist Shiladitya DasSarma of the University of Maryland School of Medicine and postdoctoral researcher Edward Schwieterman at the University of California, Riverside, argue that before green plants started harnessing the power of the sun for energy, tiny purple organisms figured out a way to do the same.
        "Alien life could be thriving in the same way," DasSarma told Live Science. He suggested that astronomers have discovered thousands of new extrasolar planets recently and in addition to examining substances such as water and air, they are developing the capacity to see surface biosignarures in the light reflected from these planets. There are already ways to detect green life from space, he said, but scientists might need to start looking for purple, too.
        The idea that the early Earth was purple is not new, DasSarma and his colleagues advanced the theory in 2007. The thinking goes like this: Plants and photosynthesizing algae use chlorophyll to absorb energy from the sun, but they don’t absorb green light. That’s odd, because green light is energy-rich. Perhaps, DasSarma and his colleagues reasoned, something else was already using that part of the spectrum when chlorophyll photosynthesizers evolved.
        That "something else" would be simple organisms that captured solar energy with a molecule called retinal. Retinal pigments absorb green light best. They’re not as efficient as chlorophylls in capturing solar energy, but they are simpler, the researchers wrote in their new paper.
        Retinal light-harvesting is still widespread today among bacteria and the single-celled organisms called Archaea. These purple organisms have been discovered everywhere from the oceans to the Antarctic Dry Valley to the surfaces of leaves, Schwieterman told Live Science. Retinal pigments are also found in the visual system of more complex animals.
        Regardless of whether the first life on Earth was purple, it’s clear that lavender life suits some organisms just fine, Schwieterman and DasSarma argue in their new paper. That means that alien life could be using the same strategy. And if alien life is using retinal pigments to capture energy, astrobiologists will find them only by looking for particular light signatures, they wrote.

选项 A、Develop the capacity to search surface biosignatures on other planets.
B、Explore new ways to detect green life from space.
C、Probe into how retinal pigments capture energy.
D、Use techniques to detect light signatures of purple.

答案D

解析 语义的理解和推断。本题关键句为“And if alien life is using retinal pigments to capture energy, astrobiologists will find them only by looking for particular light signatures”,即研究人员指出,如果外星生命用视黄醛获取能量,太空生物学者可能只能通过找寻特定的光信号才能找到外星生物,根据文章所述,其暗示为外星生命可能是紫色的,需要找寻紫光信号,选项D正确。
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