VOA慢速英语2021--辐射研究发现宇航员火星任务时间不能超过4年

Study: Mars Missions Should Be Limited to 4 Years to Protect from Radiation

A new study has found that future missions to Mars should be limited to four years to protect astronauts from harmful radiation.

The study also says that missions should be carried out during specific times to reduce the level of exposure to dangerous particles.

The U.S. space agency NASA currently has plans to send astronauts back to the moon. It also plans to one day send astronauts to Mars. Those plans include missions that would keep astronauts in space for long periods.

China has also announced plans to send astronauts to Mars by 2033. Such missions present great risks to humans because of the high level of radiation in space.

Radiation exposure can cause a series of health issues, including skin burns, heart problems and cancer. NASA has spent many years studying ways to protect human space travelers from radiation.

On Earth, we also experience exposure to radiation from the sun. But our planet's magnetic field protects us from dangerously high levels.

Two main kinds of radiation can affect humans and equipment in space. One is produced by particles released from the sun. The other comes from high energy particles created by cosmic rays from outside our solar system. NASA says the second kind can be more dangerous to humans and more destructive to equipment.

In the new study, researchers used modeling methods to predict levels of radiation exposure during future space missions. They combined geophysical models of particle radiation with models for how radiation would affect human passengers and spacecraft.

The international group of researchers recently published their study in Space Weather. The results showed that the best time for a human space flight to Mars would be during what is known as solar maximum. This is a period within the sun's magnetic cycle that experiences the most intense solar activity.

The researchers said in a statement that this period would be a good time for a flight because, "the most dangerous and energetic particles from distant galaxies¹ are deflected³ by the enhanced solar activity," during solar maximum.

The study also found that a round-trip mission to Mars should not last longer than four years. A longer mission would expose astronauts to "dangerously high" amounts of radiation, even if the trips to and from Mars were made during safer travel times. The average flight time to Mars is about nine months.

The spacecraft used for carrying astronauts to Mars would require special protective shielding, the study found. But the researchers said this protective material cannot be too heavy. If the material is too thick, it could actually increase the amount of secondary radiation the astronauts could be exposed to.

The research team included scientists from the University of California, Los Angeles (UCLA). UCLA research geophysicist Yuri Shprits was a co-writer of the study. He said the findings suggest that future missions to Mars can be safe for humans as long as they follow the research recommendations.

Shprits said, "This study shows that while space radiation imposes strict limitations on how heavy the spacecraft can be and the time of launch -- and it presents technological⁴ difficulties for human missions to Mars -- such a mission is viable⁵."

NASA is currently working to develop several kinds of solutions to protect humans serving long-term space missions. Possible solutions include building temporary shelters, developing high-tech⁶ protective clothing, or deploying⁷ special shields above Mars to block radiation.

Words in This Story

mission – n. an important task, usually involving travel

specific – adj. clearly defined or identified

exposure – n. coming into contact with something

cosmic ray – n. high-energy particles that move through space at nearly the speed of light

maximum – n. the greatest or highest amount possible

deflect² – v. to make something change direction by hitting or touching⁸ it

enhance – v. to improve something

shield – n. a piece of equipment used as protection

impose – v. to put or place

viable – n. effective and able to be successful

1 galaxies   

星系( galaxy的名词复数 )； 银河系； 一群（杰出或著名的人物）

参考例句：

• Quasars are the highly energetic cores of distant galaxies. 类星体是遥远星系的极为活跃的核心体。
• We still don't know how many galaxies there are in the universe. 我们还不知道宇宙中有多少个星系。

2 deflect   

v.(使)偏斜，(使)偏离，(使)转向

参考例句：

• Never let a little problem deflect you.决不要因一点小问题就半途而废。
• They decided to deflect from the original plan.他们决定改变原计划。

3 deflected   

偏离的

参考例句：

• The ball deflected off Reid's body into the goal. 球打在里德身上反弹进球门。
• Most of its particles are deflected. 此物质的料子大多是偏斜的。

4 technological   

adj.技术的；工艺的

参考例句：

• A successful company must keep up with the pace of technological change.一家成功的公司必须得跟上技术变革的步伐。
• Today,the pace of life is increasing with technological advancements.当今， 随着科技进步，生活节奏不断增快。

5 viable   

adj.可行的，切实可行的，能活下去的

参考例句：

• The scheme is economically viable.这个计划从经济效益来看是可行的。
• The economy of the country is not viable.这个国家经济是难以维持的。

6 high-tech   

adj.高科技的

参考例句：

• The economy is in the upswing which makes high-tech services in more demand too.经济在蓬勃发展，这就使对高科技服务的需求量也在加大。
• The quest of a cure for disease with high-tech has never ceased. 人们希望运用高科技治疗疾病的追求从未停止过。

7 deploying   

（尤指军事行动）使展开( deploy的现在分词 )； 施展； 部署； 有效地利用

参考例句：

• Provides support for developing and deploying distributed, component-based applications. 为开发和部署基于组件的分布式应用程序提供支持。
• Advertisement, publishing, repair, and install-on-demand are all available when deploying your application. 在部署应用程序时提供公布、发布、修复和即需即装功能。

8 touching   

adj.动人的，使人感伤的

参考例句：

• It was a touching sight.这是一幅动人的景象。
• His letter was touching.他的信很感人。