According to the official website of the National Aeronautics and Space Administration (NASA) recently, the United States has issued a new space policy directive, intended to promote NASA to create the next “big step for mankind”-to provide continuous power on the surface of the moon and on the moon Build a long-term base to further send astronauts to far-reaching Mars.
This space policy directive is codenamed SPD-6, and its content is “National Space Nuclear Power and Propulsion Strategy” (SNPP). The principles established by the directive include: the United States will achieve the goal of SNPP development and utilization; the development of advanced radioisotope power systems to realize power systems that can be used on planetary surfaces and can be used for solar system exploration; when the United States develops and uses SNPP-related systems The principles of safety, security, and sustainability will be adhered to; the United States will seek a roadmap for the federal government to support this strategic activity, encourage commercial activities to achieve their goals and adhere to the principle framework established in the SPD-6 directive.
NASA said that nuclear power systems can provide power for spacecraft to replace the energy that cannot meet the needs of space missions. For example, it can solve bottlenecks such as solar energy failure when the mission environment is too dark, and insufficient fuel when flying too far. Specifically, space nuclear power system includes a radioisotope power system and the nuclear reactor, which can continuously provide energy, temperature control, and propulsion power for spacecraft. The SPD-6 directive establishes a “high-level” goal, principle, and support roadmap this time to ensure that SNPP can be carried out safely, effectively, and responsibly.
“NASA firmly supports the White House’s continued leadership of the Artemis program, including sending the first woman and a man to the moon in 2024. On the moon, we will prepare for new science and space missions into the depths of the solar system. “NASA Administrator Jim Bridenstine said.
In view of this, in order to support the SPD-6 directive, NASA’s current mission is to make the nuclear power system more mature and create a “fission surface power system” for use on the moon. NASA’s Department of Energy and Industry will design, manufacture, and test a 10-kilowatt fission surface power system, and plan to test the system on the moon in the late 1920s to provide continuous power on the lunar surface and test its potential for use on Mars.
In addition, NASA is also improving nuclear thermal propulsion and nuclear power propulsion capabilities. Nuclear propulsion will provide powerful power for human exploration beyond the moon, and can significantly reduce the fuel demand. If traditional chemical propulsion is used to send astronauts to Mars, a large amount of propellant is required. In addition to reducing risks and making reactor designs more mature, NASA is also cooperating with the U.S. Department of Energy and the Department of Defense to jointly develop technologies for propulsion systems and increase nuclear fuel production capabilities.
Tianwen-1 completed the fourth midway correction of its orbit and returned the first image of Mars
At 20 o’clock on February 5, 2021, the engine of the first Mars exploration mission Tianwen-1 probe was ignited, and the fourth midway correction of the ground fire transfer section was successfully completed to ensure that Mars capture was carried out as planned.
Up to now, Tianwen-1 has been in orbit for about 197 days, about 184 million kilometers away from Earth, about 1.1 million kilometers away from Mars, and a flight mileage of about 465 million kilometers. The probe systems are in good condition.
Prior to this, Tianwen-1 acquired the first Martian image at a distance of about 2.2 million kilometers from Mars.
The potential mass range of dark matter is narrowed, helping to focus the search area
According to a report by the physicist organization network on the 27th, British scientists used the fact that gravity acts on dark matter to fundamentally calculate the mass range of dark matter for the first time. This range is much narrower than previously thought. The latest research has narrowed the range of potential masses of dark matter particles and also limited the search range for future dark matter “catchers”. It will also help scientists discover potential new forces in the future.
Dark matter does not emit light, emit electromagnetic waves, does not participate in electromagnetic interactions, and cannot be directly “seen” with any optical or electromagnetic wave observation equipment. Scientists have confirmed its existence through the effect of dark matter on galaxies. The result of the cosmic microwave background radiation observation experiment gives the proportion of dark matter in the total amount of cosmic matter. In the universe, ordinary matter accounts for only 4.9%, dark matter accounts for 26.8%, and dark energy accounts for 68.3%. Dark energy and dark matter are also considered to be two dark clouds in the physics sky at the beginning of the 21st century.
In the latest study, the research team led by Professor Xavier Kalmot of the School of Mathematics and Physical Sciences at the University of Sussex assumed that gravity is the only force acting on dark matter, and calculated that the mass of dark matter particles is between Between 10-3eV (electron volt) and 107eV, it is much narrower than the theoretically expected 10-24eV to 1028eV.
“This is the first time anyone has used quantum gravity to calculate the mass range of dark matter,” Carmott said. This study shows that unless there is a hitherto unknown force affecting it, dark matter cannot be like some theories. It is said to be “ultralight” or “overweight”.
The researchers believe that this research will benefit physicists in two ways: one is to focus on the search area of dark matter; the other is to help reveal whether there are mysterious unknown forces in the universe-if the mass of dark matter is found to exceed in the future The range predicted by the Sussex team indicates that dark matter is affected by other forces in addition to gravity.
The collapse of some marine species: sea surface temperatures continue to rise under multiple pressures
A zoology study published on the 28th in the British “Nature” magazine pointed out that some marine species are facing a crisis of “population collapse”-since 1970, the number of marine slatyfish in the world has decreased by 71%. Among these marine species, More than three-quarters of them are on the verge of extinction; and another study published at the same time pointed out the “climate crisis” of the ocean: global sea surface temperature has been rising for the past 12,000 years.
The ocean is facing multiple pressures. Issues such as climate change, rising sea temperature, pollution, overfishing, and ocean acidification have been affecting the health of the ocean. Scientists currently believe that the risk of marine species extinction should mainly come from overfishing. However, the reduction of individual species has always been difficult to measure. Although the reduction of marine and coastal plategill fish populations in different regions of the world has been recorded before, there has been no global development. analysis.
This time, the Simon Fraser University team in Canada estimated the relative abundance of 18 marine slaty fish species from 1970 to 2018 and assessed the extinction risk of all 31 marine slaty fish species. They found that from 1970 to 2018, the global abundance of marine slaty fish fell by 71.1%. Among these 31 species, 24 are on the verge of extinction; 3 shark species have declined especially, and are now classified as critically endangered—this is also the most threatened species in the World Conservation Union (IUCN) list The grade.
The researchers blamed the reduction of these species on fishing pressure, which increased 18 times during this period. The research team pointed out that immediate action should be taken to prevent “population collapse”, and specifically called on governments to implement fishing restrictions to help promote species recovery.
In the climate report published on the same day by the journal Nature, the Rutgers University of New Jersey team pointed out the “climate crisis” of the ocean. According to the report, the global average annual sea surface temperature has been rising for the past 12,000 years.
The researchers reinterpreted the two latest climate models this time and devised a method to assess the seasonal deviation of a single record, and then calculate the annual average sea surface temperature. They found that climate warming from 12,000 to 6,500 years ago was caused by the retreat of the ice sheet, while recent warming was caused by the increase in greenhouse gas emissions. The current temperature is the highest in the past 12,000 years. The temperature was similar during the last interglacial period about 125,000 years ago.
In addition to suggesting that emissions have caused the sea surface temperature to continue to rise, this study also fills a long-standing gap in the gap between climate models and data used to reconstruct historical climate changes in the Holocene.