Đề thi thử số 13 — Reading 40 câu (có bài đọc)

The 21st century has witnessed a remarkable transformation in space exploration. What was once the exclusive domain of government agencies like NASA and Roscosmos is now a thriving commercial industry led by companies such as SpaceX, Blue Origin, and Rocket Lab. This shift, often called "NewSpace," has dramatically reduced the cost of reaching orbit, opened space to private investment, and accelerated technological innovation at a pace that would have seemed impossible just two decades ago.

A key driver of the new space race has been the dramatic reduction in launch costs. SpaceX's Falcon 9 rocket, with its reusable first stage, has cut the cost per kilogram to orbit from around $20,000 in the early 2000s to as low as $2,500 today. The company's Starship vehicle, currently in development, promises to reduce costs even further—to potentially under $100 per kilogram. These savings are made possible by vertical integration, rapid iteration, and aggressive use of commercial off-the-shelf components rather than custom-built space-qualified hardware.

The commercialization of space has opened up entirely new industries. Satellite constellations like SpaceX's Starlink now provide broadband internet to remote areas where traditional infrastructure is impractical. Earth observation companies sell high-resolution imagery to farmers, insurers, and governments. In-space manufacturing, asteroid mining, and space tourism are no longer science fiction—they are emerging markets attracting billions in venture capital. Some analysts predict the global space economy could exceed $1 trillion annually by 2040.

However, the rapid expansion of commercial space activity has also raised concerns. Astronomers worry about the impact of thousands of bright satellites on ground-based observations of the cosmos. Environmentalists question the effect of rocket emissions on the upper atmosphere, particularly with the rise of methane-fueled vehicles. National security experts warn of the increasing congestion and competition in orbit, with the risk of conflict over scarce resources like valuable orbits and frequency spectrum. As the new space race accelerates, finding the right balance between commercial innovation and responsible stewardship of the space environment will be one of the defining challenges of our time.

Astrobiology, the scientific study of the origin, evolution, and distribution of life in the universe, stands at the frontier of human knowledge. While humans have long wondered whether we are alone in the cosmos, only in recent decades have tools and techniques advanced enough to make this question scientifically tractable. Researchers in this field draw on astronomy, biology, chemistry, geology, and planetary science to investigate the conditions under which life might arise and to identify promising places to look for it.

The search for extraterrestrial life focuses on environments where liquid water—an essential ingredient for life as we know it—exists or once existed. Within our own solar system, the most promising candidates include Mars, where evidence suggests that liquid water once flowed on the surface; Europa, an icy moon of Jupiter believed to harbor a subsurface ocean; and Enceladus, a small moon of Saturn that has been observed venting water vapor from its south polar region. Missions to these worlds are being planned or are already underway, carrying instruments specifically designed to detect biosignatures—chemical or physical indicators of past or present life.

Beyond our solar system, the search has expanded dramatically with the discovery of thousands of exoplanets—planets orbiting other stars. The Kepler Space Telescope and its successor, TESS, have identified thousands of confirmed and candidate exoplanets, some of which orbit within their star's "habitable zone," where conditions might allow liquid water to exist on the surface. Upcoming telescopes, including the James Webb Space Telescope and ground-based observatories with advanced spectrographs, are being used to analyze the atmospheres of these distant worlds, looking for chemical signatures that might indicate biological activity—gases like oxygen, methane, or others that, in certain combinations, are difficult to explain without life.

Despite remarkable progress, astrobiology remains a young science with profound uncertainties. The only example of life we have is life on Earth, which evolved under specific conditions that may not be representative of life elsewhere. Some scientists speculate that life could exist in forms radically different from what we know, perhaps using different chemistry or existing in environments we consider hostile. This uncertainty is both humbling and exciting, reminding us how much we have yet to learn about life, the universe, and our place within it. As technology continues to advance, the question of whether we are alone may move from philosophical speculation to scientific fact within the coming decades.

The International Space Station (ISS) is one of humanity's most remarkable achievements—a permanently inhabited microgravity laboratory orbiting Earth at an average altitude of 400 kilometers. Since the first crew arrived in November 2000, the ISS has been continuously occupied, making it the longest continuous human presence in space. The station is a partnership between five space agencies representing 15 countries: NASA (United States), Roscosmos (Russia), JAXA (Japan), ESA (Europe), and CSA (Canada).

Constructing the ISS required more than 40 assembly missions over a span of 13 years, from 1998 to 2011. The station's modular design, with pressurized sections providing living and working space equivalent to a six-bedroom house, allows astronauts from different countries to live and work together. Solar arrays extending from the station generate 120 kilowatts of power—enough to supply approximately 40 average homes. The station travels at a speed of about 28,000 kilometers per hour, completing 16 orbits of Earth every day, which means astronauts witness 16 sunrises and 16 sunsets every 24 hours.

The ISS serves primarily as a microgravity research laboratory, where scientists conduct experiments that would be impossible on Earth. Research areas include biology, biotechnology, physics, astronomy, and materials science. Some notable findings include advances in understanding muscle atrophy and bone loss in microgravity—critical knowledge for long-duration space missions—and the development of new drugs that crystallize more perfectly in space than on Earth. The station has also served as a testbed for technologies needed for future missions to the Moon and Mars, including life support systems, radiation shielding, and human-robot interaction.

However, the ISS is showing its age. Originally planned for retirement around 2015, the station has been kept operational through ongoing maintenance, with NASA extending its planned operational life to 2030. Plans for its eventual deorbit involve using a specially built spacecraft to safely guide the station into a remote area of the Pacific Ocean. Meanwhile, several private companies are developing commercial space stations to take over after the ISS is decommissioned, with the goal of creating a sustainable marketplace in low Earth orbit. The legacy of the ISS, however, will endure: it has proven that humans from diverse nations can work together in space, and it has paved the way for the next generation of space exploration.

The next era of human space exploration promises to be the most exciting yet. After decades of relatively low activity following the Apollo missions, the past 20 years have seen a renaissance in space exploration, driven by a combination of government programs and commercial innovation. NASA's Artemis program aims to return humans to the Moon by the mid-2020s, this time to stay, while private companies and international partners are developing plans for crewed missions to Mars later in the century.

The Moon is a critical stepping stone for deeper space exploration. NASA's Artemis program plans to establish a permanent lunar base at the Moon's south pole, where water ice has been detected in permanently shadowed craters. This ice can be converted into drinking water, oxygen for breathing, and even hydrogen and oxygen for rocket fuel—essentially creating a gas station in space. A lunar base would also allow scientists to study the long-term effects of low gravity on the human body and test technologies needed for the much longer journey to Mars, which takes six to nine months each way.

Mars remains the ultimate goal for human exploration in the coming decades. Unlike the Moon, Mars has a day length similar to Earth (about 24.5 hours), seasons, and an atmosphere that, while thin and mostly carbon dioxide, provides some protection from radiation. Multiple robotic missions have confirmed that Mars once had abundant liquid water and may still have subsurface ice, raising the possibility that microbial life could have evolved there in the past—or perhaps still exists. Human missions to Mars would address fundamental questions about life beyond Earth and could eventually lead to permanent human settlement, making humanity a multiplanetary species.

The challenges of sending humans to Mars are immense. The long travel time means astronauts would be exposed to cosmic radiation and the psychological effects of isolation. Landing heavy payloads on Mars is technically difficult due to its thin atmosphere. Building habitats that can withstand the harsh environment, including dust storms that can last for weeks, requires innovation in materials and engineering. Despite these obstacles, multiple organizations—including NASA, the European Space Agency, and private companies like SpaceX—are actively working on solutions. As Elon Musk has often said, becoming a multiplanetary species is essential for the long-term survival of humanity, providing insurance against existential risks that could affect a single planet. The dream of walking on Mars, once confined to science fiction, is steadily becoming a real possibility within the lifetimes of people alive today.