（带文稿）0526VOA：新发现表明火星曾经存在古老河流【文末小测】

张老邪叨哔叨：

低谷期的时候真想离开地球，坐着Space X把自己发射到火星上去种土豆啊 ~ 话说大家英文阅读一定不要挑食啊，比如四级阅读还会考病毒传播和霓虹灯、酿酒的话题等，平常训练下不同话题的语感，不要让自己的英语水平被话题坑了哦~

Geological formations are seen in sedimentary rock in the Hellas Basin on Mars. Researchers say these well-exposed channels are archived evidence of long-lived rivers active on the Martian surface over 3.7 billion yrs ago. （NASA/JPL-Caltech/UoA/Matt Balme/William）

Transcript

Scientists say they have found the most detailed evidence yet of long-flowing, ancient rivers on Mars.

The discovery supports existing evidence that Mars – which today is dry and cold – was once a water-rich planet. The researchers say their findings suggest rivers may have flowed on the surface of Mars for hundreds of thousands of years.

The evidence came from new satellite pictures of the Martian surface. These images were captured by a camera on NASA’s Mars Reconnaissance Orbiter. The camera is able to take detailed pictures of the surface while orbiting the planet from about 400 kilometers away.

A team of scientists studied the images, which showed a rocky area within the planet’s Hellas Impact Crater. An impact crater is formed when a space object crashes into a planet or moon. The Hellas Impact Crater, in the southern Martian hemisphere, is one of the largest formations of its kind in the solar system.

This image from ESA’s Mars Express shows a valley network on Mars. This oblique perspective view was generated using a digital terrain model and Mars Express data gathered on 19 November 2018 during Mars Express orbit 18831. （Image credit: ESA/DLR/FU Berl

The team was led by Francesco Salese, a geologist at Utrecht University in the Netherlands. The research results were recently published in a study in Nature Communications.

Salese said the scientists studied sedimentary rocks from a 200 meter high rocky cliff. Sedimentary rocks form when sediment, transported by water or wind, settles and forms solid rock.

“These are sedimentary rocks, 3.7 billion years old, and were formed by rivers that were likely active for over 100,000 years of Martian history,” Salese said in a statement.

“OK, it is not like reading a newspaper, but the extremely high resolution imagery allowed us to ‘read’ the rocks as if you are standing very close to the cliff,” he added.

Example of features identified in a deep basin on Mars that show it was influenced by groundwater of years ago. （Image credit: NASA/JPL-Caltech/MSSS）

Salese said even without the ability to examine the cliff area up-close on Mars, the pictures show strong similarities to sedimentary rocks found on Earth.

The researchers created three-dimensional, or 3D, images of the area to get a more detailed understanding of it. The pictures suggested that some ancient Martian rivers were several meters deep.

William McMahon is another geologist who was part of the investigation team. He said sedimentary rocks have long been studied on Earth to learn what conditions were like on our planet millions, or even of years ago.

“Now we have the technology to extend this methodology to another terrestrialplanet, Mars, which hosts an ancient sedimentary rock record which extends even further back in time than our own,” McMahon said in a statement.

Another leader of the team was Joel Davis, a researcher with Britain’s Natural History Museum. He said scientists had never before been able to examine such a rock formation with such great detail.

This May 12, 2016 image provided by NASA shows the planet Mars. （NASA/ESA/Hubble Heritage Team - STScI/AURA, J. Bell - ASU, M. Wolff - Space Science Institute via AP）

Davis said the discovery is “one more piece of the puzzle in the search for ancient life on Mars.” He added that it also provides new evidence of how much water existed on Mars in ancient times.

“The rivers that formed these rocks weren't just a one-off event - they were probably active for tens to hundreds of thousands of years,” Davis said.

Salese added that the findings show Mars had an environment able to support large, flowing rivers for extended periods of time.

“This kind of evidence, of a long-lived watery landscape, is crucial in our search for ancient life on the planet,” Salese said.

I’m Bryan Lynn.

How does the article say the new evidence on Martian rivers was discovered?

A. From new pictures captured by a Mars explorer

B. From soil samples collected by a NASA orbiter

C. From new satellite images of the surface of Mars

D. From examining new images of Martian ice

How does the article say impact craters are created?

A. By explosions or volcanic activity in space

B. When space objects crash into a planet or moon

C. By violent storms or other climate events

D. When water crashes against rocky surfaces

How did William McMahon say the study of sedimentary rocks can be valuable?

A. To learn about chemicals found in the rocks

B. To learn whether planets contains water and ice

C. To learn the exact age of rocks on the surface

D. To learn about a planet’s ancient conditions

What was one thing the researchers learned by creating three-dimensional （3D） images of the photographed area?

A. The width of the rivers

B. How much water flowed

C. The depth of the rivers

D. How rocky the cliffs were

Words in This Story

crater – n. a large hole in the ground

geologist – n. a scientist who has studied rocks and soil in order to learn about the history of planets

cliff – n. an area of high, steep rocks

sediment – n. a solid substance that forms a layer at the bottom of a liquid

resolution – n. a measure of sharpness for an image

three-dimensional – adj. appearing to have length, depth and width

terrestrial – adj. relating to the Earth, not space

host – v. to serve as a host for something

puzzle – n. a game or activity in which you have to put pieces together or answer questions using skill

crucial – n. extremely important or necessary

【CBDC】