1 . A study confirmed that the cracks (裂缝) found on the surface of Mars last year by the Curiosity Rover are evidence of ancient lakes that likely dried up about 3.5 billion years ago. The new study provides further evidence of what the climate on the Red Planet may have been like in its ancient past.
The study, published online in Geology, proved that cracks on Mars’s surface previously photographed by Curiosity are dry mud cracks which could have only been formed when wet ground was exposed to the air. This conclusion was based on an analysis of a single area of rock known as “Old Soaker.”
Researchers used the Curiosity Rover and information from its many tools including the Mars Hand Lens Imager, ChemCam Laser-Induced Breakdown Spectrometer (LIBS) and the Alpha Particle X-Ray Spectrometer (APXS) to study both the physical appearance and the chemistry of the rock, which is described as no bigger than a coffee table.
The analysis showed that cracks on the rock were formed by exposure to air, rather than heat or the flow of water. In addition, the shape of the cracks suggests it experienced a single drying event on the planet, rather than getting wet and drying over repeatedly. The position of the cracks, closer to the center of the ancient lake rather than alongside it, also suggests that the lake levels changed often, rising and falling over time.
“The mud cracks are exciting because they help us to understand this ancient lake system,” lead study author Nathaniel Stein, a geologist at the California Institute of Technology in Pasadena, said, referring to the ancient lake system on the planet.
Scientists have known of the existence of ancient water on Mars for years. A 2015 NASA study that measured water in Mars’s atmosphere suggested that ancient oceans may once have had more water than our own Arctic Ocean. However, because the planet has less gravity and a thinner atmosphere than Earth, this water evaporated into space over the course of several billion years.
1. What is the Curiosity Rover underlined in Paragraph 1?| A．A research organization. | B．An automatic machine. |
| C．An ancient remain on the planet. | D．A space telescope on earth. |
| A．The cracks are near the center of an ancient lake. |
| B．Mars was getting wet and drying more than once. |
| C．The lake level on Mars seldom changes over time. |
| D．The cracks on the rocks were formed by water flow. |
| A．Ancient water still exists on Mars now. |
| B．The gravity on Mars is stronger than that on Earth. |
| C．The atmosphere on Earth is thicker than that on Mars. |
| D．The ancient Arctic Ocean had more water than it has now. |
| A．Water on Mars. | B．A trip to Mars. |
| C．A study on Mars. | D．Cracks on Mars. |
2 . Space is becoming more crowded. Quite a few low-Earth-orbit (LEO) satellites have been launched into the sky, which are designed to move around the Earth only a few hundred kilometres above its surface. SpaceX and OneWeb plan to launch LEO satellites in their thousands, not hundreds, to double the total number of satellites in orbit by 2027.
That promises to change things on Earth. LEO satellites can bring Internet connectivity to places where it is still unavailable. This will also be a source of new demand for the space economy. Morgan Stanley, a bank, projects that the space industry will grow from $350 billion in 2016 to more than $1.1 trillion by 2040. New Internet satellites will account for half this increase.
For that to happen, however, three worries must be overcome. Debris (碎片) is the most familiar concern. As long ago as 1978, Donald Kessler, a scientist at NASA, proposed a scenario (设想) in which, when enough satellites were packed into low-Earth orbits, any collision could cause a chain reaction which would eventually destroy all spacecraft in its orbital plane. Solutions exist. One solution is to grab the satellites with problems and pull them down into the Earth’s atmosphere. Another is to monitor space more closely for debris. But technology is only part of the answer. Rules are needed to deal with old satellites safely from low-Earth orbits.
Cyber-security is a second, long-standing worry. Hackers could take control of a satellite and steal intellectual property, redirect data flows or cause a collision. The satellite industry has been slow to respond to such concerns. But as more of the world’s population comes to rely on space for access to the Internet, the need for action intensifies. Measures will surely be taken to protect network security.
The third issue follows from the first two. If a simple mistake or a cyber-attack can cause a chain reaction which wipes out hundreds of billions of dollars of investment, who is responsible for that? Now the plans of firms, wishing to operate large numbers of satellites are being studied. But there is a long way to go before the risks are well understood, let alone priced.
As space becomes more commercialized, mind-bending prospects open up: packages moved across the planet in minutes by rocket rather than by plane, equipment sent to other small planets, passengers launched into orbit and beyond. All that and more may come one day. But such activities would raise the same questions as LEO satellites do. They must be answered before the space economy can truly develop.
1. What can we learn about LEO satellites from the passage?| A．They will limit the space economy |
| B．They will increase in large numbers. |
| C．They will move beyond the Earth as far as possible. |
| D．They will monitor old satellites. |
| A．To avoid network attack. |
| B．To make the Internet accessible to backward areas. |
| C．To lighten the financial burden of space firms. |
| D．To accelerate the development of bank industry. |
| A．block low-Earth orbits with packed satellites |
| B．pull down satellites into Earth’s atmosphere |
| C．put the disposal of old satellites at high risks |
| D．bring destruction to spacecraft in the same orbit |
| A．It should be further confirmed for its ownership. |
| B．It should be continued because of its advantages. |
| C．It should be done carefully to avoid potential risks. |
| D．It should be stopped in the face of the space economy. |
3 . Scientists who study the Sun watch for sunspots—violent storms that can affect communications，navigation systems and even electric power stations on the Earth.
Sunspots are a product of huge electromagnetic storms on the Sun. Scientists on the Earth are able to observe sunspots eight minutes after they happen. That is how long it takes for the Sun’s light to reach us.
The first electrically charged particles (颗粒）from a sunspot enter the Earth’s atmosphere about 20 to 30 minutes after the storm happens. These particles can harm human beings. So before they arrive, astronauts on the International Space Station move into special areas designed to protect them from their effects.
About a day or two later, the biggest part of the storm arrives. It is called a coronal mass ejection. “That is billions of tons of solar material that's blown away from the Sun. It’s traveling millions of kilometers an hour, but that is relatively slow.” says Alex Young, the Associate Director for Science at NASA's Heliophysics Science Division.
Several civilian government agencies and the U.S. Air Force watch weather conditions in space 24 hours a day. NASA does so because it must protect its astronauts and the electronic devices on its spacecraft.
Scientists are also trying to understand why the number of sunspots rises and falls at almost regular intervals every 11 years. In other words, scientists can almost predict the amount of solar activity. Sometimes the intensity (强度）is higher，sometimes lower，For example, the current solar cycle, as it is called, is much lower than the previous one.
Several satellites watch the Sun and the environment between the Sun and tho Earth. Pictures and other information from the satellites tell scientists what is happening on and near the Sun.
Alex Young says we have only been looking at the Sun with powerful instruments for about 30 to 40 years. Thai is a very short time compared to ll\o four billion years that tho star has been shining.
1. Why do astronauts on International Space Station move into special area?| A．To avoid being harmed. | B．To charge the battery. |
| C．To watch the Sun closely | D．To protect devices on the spacecraft. |
| A．About 8 minutes. | B．About 20 to 30 minutes |
| C．About 11 years. | D．About 30 to 40 minutes |
| A．Environmental changes. | B．Good weather conditions |
| C．Advanced instruments. | D．Government agencies |
| A．The role of satellites. | B．findings about sunpots |
| C．Observation of space. | D．Communication on the earth. |
