Final preparations are under way for China to launch an uncrewed craft to visit both an asteroid and a comet, in the hope of learning more about the space rocks in our solar system.

The Tianwen-2 mission by the China National Space Administration (CNSA) will collect a 100-gram sample from the asteroid Kamoʻoalewa and return it to Earth. After dropping off the sample, the probe will use our planet’s gravity as a slingshot��to boost itself towards the comet 311P/PanSTARRS, which it will observe remotely.

The mission is due to launch from the Xichang Satellite Launch Center in Sichuan province . It won’t be the first to return samples of asteroids to Earth, as both NASA’s OSIRIS-REx and JAXA’s Hayabusa missions have already done that. But it will be China’s first mission to an asteroid involving the return of a rock sample, and it is likely to be the first mission to a unique type of body called a quasi-satellite.

Quasi-satellites like Kamoʻoalewa don’t strictly orbit Earth, but travel in a similar orbit to us around the sun, swinging elliptically around our planet as they do so. This unusual situation has led scientists to suspect that this particular one is a chunk of the moon ejected millions of years ago by an asteroid impact.

On the other hand, has an asteroid-like orbit – spinning around our sun in the asteroid belt between Mars and Jupiter – but with an appearance more like a comet because it has tails. These are suspected of being bits of dust and rubble flung out from its spinning body.

The CNSA that 311P/PanSTARRS is a “living fossil”, making it useful for studying the early material composition, formation process and evolutionary history of the solar system. And Tianwen-2 will provide scientists with a better understanding of both Kamoʻoalewa and 311P/PanSTARRS. However, the results won’t come quickly: the craft is due to reach 311P/PanSTARRS in 2034, and even the Kamoʻoalewa sample is expected to return to Earth only in late 2027.

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Exactly how much the CNSA will share about the discoveries is also unclear. at the University of Birmingham, UK, says the mission’s outline is known, and one likely goal is to study the differences between the asteroid and the comet to gain a deeper understanding of the range of bodies in our solar system, but precise details haven’t been forthcoming.

Alconcel’s previous experience working with the CNSA on the leads her to suspect that the agency will hold on to the resulting scientific data tightly. “It was extremely difficult to negotiate [with the CNSA],” says Alconcel.
”Once they kind of had some information from us, they were not very keen to reciprocate. There will not be a public repository of this data, I don’t think.”

She says that the mission is daring, as Kamoʻoalewa is spinning, which will make landing harder. Navigation algorithms are likely to demand such powerful computers that images and sensor readings will be sent back to Earth for computation. “If we were to always pick lovely, cooperative objects, we wouldn’t learn a lot,” she says. “There’s a lot that could potentially go wrong.”

The CNSA didn’t respond to New Scientist‘s request for interview.

Dementia rates are increasing more rapidly in China than almost anywhere else in the world, with cases more than quadrupling in the country over the past few decades.

at Fudan University in China and her colleagues analysed dementia rates in 204 countries and regions around the world between 1990 and 2021. They used a World 91ɫ��Ƭ Organization database to collect information on dementia deaths and cases in people aged 40 and older, focusing on Alzheimer’s disease and some other forms of dementia, such as vascular dementia and frontotemporal lobe dementia.

The researchers found that the number of people with dementia worldwide more than doubled during this period, from almost 22 million in 1990 to close to 57 million in 2021. The increase was even more drastic in China, where cases more than quadrupled, rising from roughly 4 million to nearly 17 million over the same time frame.

Further analysis revealed that population growth was the main culprit. Birth rates in China spiked in the 1950s. “So those people are getting older today – they are now in their 70s, which is the highest risk group for dementia,” says at Yale University, who wasn’t involved with the study. “Many countries have baby boomers, but not as large a cohort as China’s baby boomers. So that’s the main issue.”

The team identified three other major factors contributing to China’s rising dementia rates. The first, smoking, almost exclusively affects men, as only 2 per cent of women in China smoke cigarettes while . This is in sharp contrast to wealthier countries such as the US and the UK, where smoking rates have steadily declined, says Chen.

One Western trend that China has echoed is a jump in rates of diabetes and obesity, particularly in the past few decades, both of which are risk factors for dementia. This is probably because people in China are adopting a more Western diet high in fats and calories, says Chen. He believes that dementia rates in China will eventually resemble those in the US or UK, as younger generations tend to smoke less than older ones. But the condition will still have a huge impact on China in the meantime.

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“Dementia is one of the most expensive diseases in the world. It requires a lot of caregiving and treatment,” says Chen. “And in terms of an ageing population, China is still the largest in the world. There are fewer young people taking care of a larger cohort of older people with dementia. So, these are all challenges.”

China’s vast electrical grid buzzes with more renewable energy than that of any other country, but this system is also becoming more vulnerable to power shortages caused by unfavourable weather. The need to ensure a reliable power supply could push China’s government to use more coal-fired power plants.

China’s energy system is rapidly getting cleaner, with virtually every month setting new records for wind and solar energy generation. The country’s overall greenhouse gas emissions – the world’s highest – are expected to soon peak and begin to decline. Wind, solar and hydropower currently make up about half of China’s power generation capacity, and are expected to increase to almost 90 per cent by 2060, when the country has pledged to reach “carbon neutrality”.

This growing reliance on renewable energy also means the country’s power system is increasingly vulnerable to changes in the weather. Intermittent wind and sun can be supplemented by steadier hydropower, produced by huge hydroelectric dams concentrated in southern China. But what happens when a wind and solar slump coincides with a drought?

at Dalian University of Technology in China and his colleagues modelled how power generation on the increasingly renewable grid would respond to these “extreme weather” years. They estimated how the country’s current and proposed future mix of wind, solar and hydropower would behave under the least favourable weather conditions seen in the past.

They found that the future grid would be substantially more sensitive to changes in the weather than today. In the worst case weather scenario, power generation could decline by as much as 10 per cent, leading to power shortages. In 2030, a year with the least favourable weather would result in an energy shortage of more than 400 terawatt-hours, nearly 4 per cent of total energy demand. “That’s not a number that anyone can just ignore,” says at the Asia Society Policy Institute in Washington DC.

In addition to an overall lack of power, droughts could specifically limit the amount of hydropower available to smooth out irregular wind and solar generation. This could also lead to power shortages. “It is essential to equip the power grid with a proper proportion of stable power sources that are less affected by meteorological factors to avoid large-scale extensive electricity shortages,” the researchers wrote in their paper.

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One way to help would be to move surplus electricity between provinces more efficiently. Expanding the transmission infrastructure to do so could eliminate the risk of power shortages on today’s grid and cut the risk in half by 2060, the researchers found. Adding tens of millions of kilowatts of new power capacity, whether using batteries or other methods, would also mitigate against hydropower droughts, they found.

The amount of additional storage China will need to add in order to achieve carbon neutrality “will be an astronomical number”, says Li.

While these changes will be difficult, adding that much storage is feasible given the huge volume of batteries already being produced in China, says at the Centre for Research on Energy and Clean Air in Finland. He says the country is also building 190 gigawatts of pumped hydro power capacity, which can provide longer-term energy storage by pumping water above a dam using surplus electricity, then releasing it when more power is needed.

However, to date, power shortages have mainly spurred China’s government to build more coal-fired power plants. In 2021 and 2022, for instance, hydropower droughts and heatwaves raised power demand enough to cause severe blackouts, creating political pressure for a . In 2023, record-low hydropower generation led to record-high emissions.

China’s president Xi Jinping has said coal power would peak this year, but entrenched political support for the power source makes this a difficult prospect. “If China suffers another round of those episodes, more coal-fired power plants should not be the answer,” says Li. “It’s just hard to phase out coal; China loves coal.”