1 . Asteroids (小行星) are believed to have formed early in our solar system’s history — about 4.5 billion years ago — when a cloud of gas and dust called the solar nebula (太阳星云) collapsed and formed our sun and the planets. By visiting these near Earth objects to study the material that came from the solar nebula, we can look for answers to some of humankind’s most arresting questions, such as:   How did the solar system form and where did the Earth’s water and other organic materials such as carbon come from? In addition to unlocking clues about our solar system, asteroids may provide clues about our Earth. By understanding more about asteroids, we may learn more about past Earth impacts and possibly find ways to reduce the threat of future impacts.

If we don’t want to go the way of the dinosaurs someday, we need to protect ourselves against the threat of being hit by a big asteroid. According to NASA, typically about once every 10,000 years, a rock y or iron asteroid the size of a football field could crash into our planet and possibly cause tidal waves big enough to flood coastal areas.

But what we really have to fear is asteroids about 328 feet across or bigger. Such an impact would cause a firestorm and fill the atmosphere with sun-blocking dust, which would wipe out forests and farm fields and starve the human and animal life that it didn’t immediately kill.

That’s why it’s vital to develop a way to neutralize such a threat to Earth. NASA’s Double Asteroid Redirection Test, launched in late November 2021, was the first mission to demonstrate a technology called asteroid redirection by manmade impactor. A robotic spacecraft will be crashed into an asteroid named Didymos, in an effort to show that it’s possible to slightly change the path of an asteroid. That would enable NASA to redirect potential threats to miss Earth.

2 . If your cellphone suddenly stops working, don't blame the service provider. The malfunction(故障) might have been caused by something bigger—a solar storm. Experts expect that the earth will see more solar activities in the near future. The malfunction of electronic devices is just one of the effects.

Sunspots(太阳黑子) serve as an indicator(标志) of the sun’s activity. For the past two years, sunspots have mostly been missing. Their absence, the longest in nearly 100 years, has taken even sun watchers by surprise.

When the number of sunspots drops at the end of each 11-year cycle, solar storms die down and all become much calmer. This "solar minimum" doesn’t' t last long. Within a year, sunspots and solar storms begin to build toward a new crescendo—the next solar maximum.

What's special about this latest cycle is that the sun is having trouble starting the next solar cycle. The sun began to calm down in late 2007, so no one expected many sunspots in 2008. They should return in 2010. Scientists have predicted that the next solar cycle could be the most active on record: more sunspots and more solar storms. However, sunspots are mostly missing now

Since the earth is in close contact with the sun, strong solar activities can bring trouble to our life. People of the 21st century rely on high-tech systems for the basics of daily life. Air travel and radio communications can be affected by strong solar activities. A big solar storm could cause 20 times more economic damage than Hurricane Katrina.

What the sun will do next is beyond our ability to predict. Most astronomers think that the solar cycle will go on but at low level. However, there is also evidence that the sun is losing its ability to produce sunspots. By 2015, they could be gone altogether.