3 . A new study focuses on K2-18b, an exoplanet(系外行星) discovered in 2018, which orbits a red dwarf star close enough to receive about the same amount of radiation from its star as Earth does from our sun.

Recently, scientists have discovered gas giants that have water in their atmospheres, but this is the least giant planet ever to have water detected in its atmosphere. “The water detection was quite clear to us relatively early on,” lead author Bjorn Benneke, a professor at the Institute for Research on Exoplanets at the Universite de Montreal, told Space.com in an interview.

“Studies have suggested that planets with hydrogen-rich atmospheres could host certain forms of life.” Benneke said. However, “K2-18b’s large atmosphere is extremely thick and creates high-pressure conditions, which likely prevents life as we know it from existing on the planet’s surface.” a news release reads. While these researchers found evidence for liquid water clouds on K2-18b, because of its lack of surface, rain wouldn’t pool on the planet. Without a real surface, so to speak, landing on the planet would also be nearly impossible to land on, especially because the gas is so thick and has such an incredibly high pressure that any Earth-created spacecraft sent there would be destroyed.

Benneke suggests that, possibly, this planet formed by rock absorbing large amounts of gas, “like a vacuum cleaner,” he said. The gas absorbed would have more than doubled the planet and increased its volume Warren eightfood.

To come to these conclusions, the research team analyzed data from Hubble Space Telescope observations that they made between 2019 and 2020 of the K2-18b planet passing in front of its star eight times. This type of research, Benneke said, is leading toward a final goal of “being able to study real, true earth-like planets.” We are not quite there yet, he said, but this is really exciting.”

4 . Just as it does on Earth, it snows on Mars. However, scientists have found that Martian snow is “dustier” than it is on Earth, which could mean it’s warmer and more likely to melt into water, a new study suggests.

“There is a chance that this dusty and dark ice might melt a few centimeters down,” said the study’s lead author, Aditya Khuller, in a statement.

In June, a separate study suggested that there maybe more water on the Red Planet than previously thought, including “dozens” of lakes less than a mile beneath the surface of the Red Planet.

The scientists believe that the ice that was dug up by the Phoenix lander in 2008 (and subsequent falling snow) occurred from a snowfall sometime over the past million years.

“It is widely believed that Mars has experienced multiple ice ages throughout its history, and it looks like the ice being exposed throughout the mid-latitudes of Mars is a relic of this ancient dusty snowfall,” Khuller added.

If researchers are able to better learn about the prospects of water on Mars, then they may be able to better learn about its prospects for once hosting life.

“Characterizing these properties can significantly improve models of ice stability on Mars and inform us about its age and origin,” the researchers wrote in the study.

The researchers say that more work is required to determine if the ice actually melts into water.

Kuller added, “We are working on developing improved computer simulations of Martian ice to study how it evolves over time, and whether it might melt to form liquid water. The results from this study will be integral to our work because knowing how dark the ice is directly influence how warm it gets.”

Although scientists confirmed in 2018 that Mars still has lakes filled with liquid water, it has been somewhat difficult to find.

5 . A newly discovered planet looks just right for life as we know it, according to an international group of astronomers. Orbiting a star about 500 light-years away, the planet called Kepler-186f is about the same size as Earth. It orbits its star at the right distance for liquid water on the surface. That is a necessary condition for life as we know it.

But it is not exactly like Earth, NASA planetary scientist Elisa Quintana said. "It's more of an Earth's cousin. It's not an Earth's twin. It shares the same characteristics as Earth, but their parent stars are very different," said Quintana.

Kepler-186f orbits a star that is smaller and cooler than our sun. But, writing in the journal Science, the astronomers say the planet appears to be a closer relative than   most of the hundreds of others discovered so far. Some are massive gas-covered giants with thick, crushing atmospheres. Others orbit too close to their stars and are too hot for life.

Two planets discovered last year are in the right orbit and might be good candidates for life, Quintana says, but they are a bit bigger than Earth. "For the first time, we can actually say we now have a planet that is both Earth-sized and orbits in its star's habitable zone," she said.

It may be the first time, but it probably is not the last, says Massachusetts Institute of Technology astrophysicist Sara Seager. "We've been waiting decades to understand how common habitable planets might be, and it's looking like they're really common. And this gives us excitement and motivation to take the next step," said Seager.

The next step would be to look for signs of life in the atmospheres of these distant   worlds. That would take a more sophisticated (高端的；复杂的) space telescope. But budget cuts threaten that mission, says University of California at Los Angeles astrophysicist Ben Zuckerman, "In principle, we could do this in the next few decades. But in practice, because there's no money, it's not gonna happen. It's not gonna happen in my lifetime, for example."

Leaving earthbound concerns behind, NASA's Elisa Quintana believes that when the next-generation space telescope is launched, it will find that we are not alone in the universe.

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    1    (study) the asteroid predict in a new study that there is very little chance that Bennu    2    (hit) Earth in the coming century.

Bennu and other asteroids are considered near Earth objects. Scientists identify such objects    3    those having the possibility of coming within 50 million kilometers of Earth's orbit. Bennu    4    (discover) in 1999. It is believed    5    (form) more than 4.5 billion years ago. It moves into near-Earth space because of gravitational interactions with other    6    (planet). Bennu makes its closest pass to Earth every six years.

The latest data on Bennu was collected by NASA's Osiris- Rex spacecraft,    7    spent more than two years observing the asteroid. Last October, Osiris-Rex also    8    (success) collected samples (样本) from Bennu. The spacecraft is now on a trip back to Earth, with NASA expecting its    9    (arrive) in September 2023. The main goal of the Osiris-Rex mission was to collect the samples. Scientists say they hope    10    material can help them better understand how the planet formed and how life began on Earth.

8 . Edmund Halley was an English scientist who lived over 200 years ago. He studied the observations of comets which other scientists had made. The orbit of one particular comet was a very difficult mathematical problem. He could not figure it out. Neither could other scientists who dealt with such problems.

However, Halley had a friend named Newton, who was a brilliant 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.

Now Halley set to work. He figured 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 had died some years before. Ever since then that comet has been called Halley’s comet, in his honor.

9 . Many of us think, wrongly, that the moon doesn't change. For example, the Tang Dynasty poet Zhang Ruoxu once wrote that “Generations have come and passed away; from year to year the moons look alike, old and new.”

However, a new study published in the journal Nature Geoscience shows that the moon is in fact slowly shrinking over time. For the study, a group of US scientists examined and analyzed thousands of photographs taken by the NASA orbiter Lunar Reconnaissance Orbiter Camera. They found that there were lots of faults on the surface of the moon. These faults were formed by recent movement on the moon.

According to NASA, the moon is made up of pieces of rocks with a hot core. The moon continued to expand as it was born. But in this process, it released energy and cooled down. Then it began to shrink, like a grape shrinking into a raisin. Over the past several hundred million years, it has become46 meters "skinnier". But due to its hard and rocky crust, the moon's surface continues to push up. "Some of these quakes can be fairly strong around five on the Richter scale,” said Thomas Watters, a senior scientist at the Smithsonian Institutions National Air and Space Museum in the US.

But does that mean the moon is a dangerous place that human shouldn't try to explore and live on in the future? “Maybe not,” reported The Telegraph. “This isn't anything to worry about. The moon may be shrinking, but not by much. It's not going anywhere,” Watters comforted us.

The new discovery proves that the idea that the moon is a dead, boring place is wrong. “We have been to the moon and we've done some great science, but there is still a lot we don't know. The moon is shrinking-we didn't really realize that until recently. It's a much more active and interesting place than we thought and we should explore that,” NASA scientist Nathan Williams said.