(点击右边的三个点，可以下载音频和调整播放速度)

（↑点击上面在线试听今天的音频，音频播放器已经支持暂停、快进、后退功能了）

听力参考原文 ↓↓↓

[00:00.04]A new study suggests that Venus

[00:04.20]likely never had water flowing on its surface.

[00:08.84]The research was based on data

[00:12.76]related to the chemical makeup

[00:15.48]of the planet's atmosphere.

[00:18.36]Scientists have long considered

[00:21.92]whether Venus once held liquid water,

[00:25.72]even possibly large oceans.

[00:29.16]Such research was based on the fact

[00:32.88]that Venus is like our own planet in many ways.

[00:38.04]It is a rocky planet similar

[00:40.84]in structure and size to Earth

[00:43.88]and is also our closest planetary neighbor.

[00:48.84]But the latest study provides evidence

[00:52.80]that Venus has likely always been the hot,

[00:56.96]extremely dry planet it remains today.

[01:02.08]Researchers from Britain's

[01:05.00]University of Cambridge led the study.

[01:08.88]It recently appeared in the publication

[01:12.76]Nature Astronomy.

[01:15.04]The researchers' data examinations

[01:19.24]led them to conclude that both the surface

[01:23.52]and interior of Venus remain dry.

[01:27.84]The team said the strongest evidence that Venus

[01:32.60]once had large amounts of water

[01:35.32]would be the discovery of some water

[01:38.56]inside the planet today.

[01:41.16]But the study provided no evidence of that.

[01:45.84]Since water is considered

[01:48.52]an important element for supporting life,

[01:51.80]the researchers also suggest that Venus

[01:55.96]was likely never habitable,

[01:58.96]or able to support life.

[02:02.00]The lead writer of the study

[02:04.84]was Tereza Constantinou,

[02:07.96]a doctoral student at the University

[02:10.92]of Cambridge's Institute of Astronomy.

[02:15.08]She told Reuters news agency,

[02:18.60]"We suggest that a habitable past

[02:22.16]would be associated with Venus'

[02:25.32]present interior being water-rich,

[02:28.60]and a dry past with Venus'

[02:31.64]present interior being dry."

[02:34.92]The researchers explained they attempted

[02:39.28]to measure the current destruction rate

[02:42.20]of molecules in water, carbon dioxide

[02:46.60]and carbonyl sulfide in Venus' atmosphere.

[02:50.96]The state of the planet's atmosphere

[02:54.20]is linked to volcanic activity, the team said.

[02:59.16]"Volcanism, through its supply of gases

[03:03.36]to the atmosphere, provides a window

[03:06.52]into the interior of rocky planets like Venus,"

[03:10.96]the researchers wrote in a statement.

[03:14.36]"As magma rises from the mantle to the surface,

[03:18.96]it releases gases

[03:21.20]from the deeper portions of the planet."

[03:24.36]Volcanic explosions, or eruptions,

[03:28.76]can provide information on the amount of water

[03:32.88]contained deep below a planet's surface,

[03:37.12]the scientists said.

[03:40.00]On Earth, for example,

[03:42.24]volcanic eruptions mostly release steam,

[03:46.60]a vapor created when water gets heated.

[03:50.36]Measurements of volcanic gases on Earth

[03:54.68]have shown they release about

[03:57.16]60 percent water vapor.

[04:00.08]But the researchers said their examinations

[04:04.32]suggested volcanic gases released on Venus

[04:08.96]were less than 6 percent water vapor.

[04:12.96]This persuaded the team to conclude

[04:16.60]that the planet's interior

[04:18.88]– the source of the magma

[04:20.80]that releases volcanic gases

[04:23.48]– must be very dry.

[04:26.44]The team noted that scientists

[04:30.20]have had two leading theories

[04:32.76]on the history of water on Venus.

[04:36.12]The first is that the planet

[04:39.04]had a moderate climate for billions of years,

[04:42.80]with liquid water flowing over areas of the surface.

[04:47.68]Over time, widespread volcanic activity

[04:52.00]likely led to extreme heat and dry conditions

[04:56.52]that made the water disappear.

[04:59.72]The second theory imagined Venus

[05:03.24]as being very hot from the beginning,

[05:06.36]preventing liquid water

[05:08.52]from ever forming on the surface.

[05:11.72]Constantinou said, "Both of those theories

[05:16.40]are based on climate models,

[05:19.04]but we wanted to take a different approach

[05:22.16]based on observations of

[05:24.64]Venus' current atmospheric chemistry."

[05:28.56]She added that the team did not find evidence

[05:33.20]that any chemicals being removed

[05:35.84]from the atmosphere were later being restored.

[05:40.44]This provides strong evidence that Venus

[05:44.32]has a very dry interior today,

[05:47.48]the scientists concluded.

[05:50.28]"The atmospheric chemistry suggests

[05:54.28]that volcanic eruptions on Venus

[05:57.40]release very little water,

[05:59.92]implying that the planet's interior

[06:03.16]...is equally dry," Constantinou said.

[06:07.40]She added that her team

[06:10.28]"would have loved to find that Venus

[06:13.52]was once a planet much closer to our own."

[06:17.40]However, Constantinou noted

[06:20.44]the finding suggests that researchers

[06:23.92]should center their searches

[06:26.60]"on planets that are mostly likely

[06:29.60]to be able to support life

[06:32.00]– at least life as we know it."

[06:35.60]I'm Bryan Lynn.

_______________________

Words in This Story

magma– n. hot liquid rock found just below the surface of the Earth

mantle – n. a layer of something that covers a surface

vapor– n. many small drops of liquid that form in the air

approach – n. the way something is done

imply– v. to communicate an idea or feeling without saying it directly