1 . Water makes up 71% of the Earth’s surface, but no one knows how or when such massive quantities of water arrived on the Earth. A new study published in the journal Nature brings scientists one step closer to answering that question.
Led by University of Maryland Assistant Professor of Geology Megan Newcombe, researchers analyzed melted meteorites (熔化的陨石) that had been floating around in space since the solar system’s formation 4.5 billion years ago. They found that these meteorites had extremely low water content — in fact, they were among the driest materials ever measured outside the Earth.
These results, which let researchers rule them out as the primary source of the Earth’s water, could have important information for the search for water — and life — on other planets. It also helps researchers understand the unlikely conditions making the Earth a livable planet.
Researchers wanted to understand how our planet managed to get water because it’s not completely obvious. Getting water and having surface oceans on a planet that is small and relatively near the sun is a challenge.
“We knew that plenty of outer solar system objects were differentiated, but it was sort of secretively assumed that because they were from the outer solar system, they must also contain a lot of water,” said Sune Nielsen, a study co-author and geologist at the Woods Hole Oceanographic Institution. “Our paper shows this is definitely not the case. As soon as meteorites melt, there is no remaining water.”
The findings have applications beyond geology. Scientists of many fields — and especially exoplanet (系外行星) researchers — are interested in the origin of the Earth’s water because of its deep connections with life.
“Water is considered to be a must for life to be able to exist, so as we’re looking out into the universe and finding all of these exoplanets, we’re starting to work out which of those planetary systems could be potential hosts for life,” said Newcombe. “In order to be able to understand these other solar systems, we want to understand our own.”
1. What did the new study focus on?| A．The history of the Earth. | B．The origin of the Earth’s water. |
| C．The source of meteorites. | D．The structure of solar system. |
| A．The driest materials coming from other planets. |
| B．An impossible source of the Earth’s water. |
| C．The challenge of getting water near the sun. |
| D．The likely conditions making the Earth habitable. |
| A．Because it is closely related to life. |
| B．Because it can make them famous. |
| C．Because it concerns many disciplines. |
| D．Because it is deeply connected with outer space. |
| A．A science fiction. | B．A geography textbook. |
| C．A book review. | D．A research report. |
The US space agency NASA says new data from observations of the asteroid (小行星) Bennu still suggests that the object could one day hit Earth. But, the scientists
Bennu and other asteroids are considered near Earth objects. Scientists identify such objects
The latest data on Bennu was collected by NASA's Osiris- Rex spacecraft,
China and the United Arab Emirates(UAE) sent
The trips to Mars come at a time when both countries have made quick progress in space programs.China's space program brought moon rocks back to Earth in December.That is the first time that a spacecraft
China's spacecraft will send a vehicle, called a rover, to land on the Marian surface. The goal is to search for
4 . Edmund Halley was an English scientist who lived over 200 years ago. Some scientists had already observed comets then, and Halley studied them carefully. The orbit (轨道) of one special comet was a very hard mathematical (数学的) problem. He couldn’t work it out. Neither could other scientists who dealt with such problems.
However, Halley had a friend named Newton, who was an excellent mathematician. Newton thought he had already worked out that problem, but he could not find the papers on which he had done it. He told Halley that the orbit of a comet had the shape of an ellipse (椭圆).
Now Halley set to work. He worked out the orbits of some of the comets that had been observed by scientists. He made a surprising discovery. The comets that had appeared in the years 1531, 1607, and 1682 all had the same orbit. Yet their appearances had been 75 to 76 years apart.
This seemed very strange to Halley. The different comets followed the same orbit. The more Halley thought about it, the more he thought that there had not been three different comets, as people thought. He decided that they had simply seen the same comet three times. The comet had gone away and had come back again.
It was an astonishing idea! Halley felt certain enough to make a prediction of what comet would happen in the future. He decided that this comet would appear in the year 1758. There were 53 years to go before Halley's prediction could be tested. In 1758 the comet appeared in the sky. Halley did not see it, for he has died some years before. Ever since then that comet has been called Halley's comet, in his honor.
1. Halley made his discovery ________.| A．by using the work of other scientists | B．through his own careful observation |
| C．by doing some experiments secretly | D．by figuring out some hard problems |
| A．1607 | B．1682 | C．1705 | D．1811 |
| A．Halley and other scientists | B．the orbit of a comet |
| C．Newton and Halley | D．Halley and his discovery |
| A．The orbit of a comet was a round shape. |
| B．Halley did not live up to the year 1758. |
| C．Halley was an Australian mathematician. |
| D．Halley worked out the comet’s orbit first. |
