{"text":[[{"start":6,"text":"Plato once observed that astronomy “compels the soul to look upwards and leads us from this world to another”. Soon a cosmic voyage bearing the ancient Greek philosopher’s name will gaze at stars many light years away as part of an expanding quest to find planets like our own."}],[{"start":24.3,"text":"The European Space Agency’s Plato satellite is due to launch early next year, armed with an array of 26 high-specification cameras. They will scan the thousands of so-called exoplanets — worlds beyond our solar system."}],[{"start":37.35,"text":"The programme is a sign of how rapidly knowledge of the cosmos is advancing. The first planet orbiting another star was discovered only in 1992. Plato is part of a historic effort to identify distant Earthlike worlds that hold lessons for our planet’s future and may even be capable of hosting life. "}],[{"start":55.5,"text":"“The main goal is to understand to what extent our solar system is different from other systems or not,” says Ana Heras Pastor, project scientist for the Plato mission. "}],[{"start":67.4,"text":"Plato is part of what Reid Wiseman, commander of Nasa’s Artemis II mission, has hailed as a “golden age” of space travel. Last month the Artemis crew rounded the far side of the Moon, just as their predecessors in the Apollo programme did more than half a century ago in a previous era of extraterrestrial ambition. "}],[{"start":null,"text":"

"}],[{"start":87.05000000000001,"text":"Today’s capabilities and ambitions dwarf anything contemplated at the time of the first human lunar landing in 1969, when the only known worlds were those that orbited the Sun."}],[{"start":99.4,"text":"Rapid technological advances in rockets, telescopes, satellites, AI and robotics mean scientists can probe outer space like never before. At the same time, public and private funding for space programmes has risen steadily, especially in the US and China, which both plan on landing people on the Moon by the end of the decade."}],[{"start":119.75,"text":"Both powers have their sights on the potential gains from the so-called lunar economy. PwC, the consultancy, projects total cumulative revenues of between $94bn and $127bn from activities such as mining and tourism over the 25 years to 2050. "}],[{"start":null,"text":""}],[{"start":138.4,"text":"Billionaire-funded space ventures have brought the idea of space travel for non-astronauts into the realm of highly privileged reality, while scientists continue the search for extraterrestrial life, notably in the clouds shrouding the planet Venus."}],[{"start":151.70000000000002,"text":"Between the first exoplanet discovery and Artemis II splashing down last month, scientists identified more than 6,000 other planets — themselves a tiny fraction of the more than 100bn believed to exist in the Milky Way galaxy. "}],[{"start":167.65,"text":"By studying these distant worlds, scientists hope to find insights into the Earth’s own environmental and geological systems. "}],[{"start":null,"text":"

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"}],[{"start":175.8,"text":"The distances to exoplanets are almost unfathomable to the imagination — and unreachable by human-made spacecraft in the foreseeable future. "}],[{"start":184.60000000000002,"text":"The nearest known exoplanet is more than four light years away. By comparison, the Voyager 1 probe, which left Earth almost half a century ago in 1977, will only this year reach one light-day’s distance from Earth."}],[{"start":199.50000000000003,"text":"A crucial new tool in the exoplanet search is the James Webb Telescope launched in 2021 as an international collaboration between the US, European and Canadian space agencies."}],[{"start":null,"text":""}],[{"start":213.05000000000004,"text":"It orbits the Sun 1.5mn km from Earth, about four times further from the planet than the Moon. To avoid becoming too hot, it deploys a tennis court-sized sunshield. "}],[{"start":226.90000000000003,"text":"From its protected vantage point, the telescope can detect and analyse light emissions from exoplanet systems using a technique known as spectroscopy to make out the composition of far-off worlds. "}],[{"start":238.35000000000002,"text":"It relies on the way every chemical substance interacts with light in a unique way, depending on its structure. Each element or molecule has a signature spectroscopic readout, like a fingerprint or barcode. "}],[{"start":251.10000000000002,"text":"Such observations and others, including from ever more sophisticated ground-based telescopes, suggest exoplanets have extraordinary variety. "}],[{"start":260.35,"text":"Claimed finds range from watery worlds that could host living creatures to sulphurous spheres that seem hellish to humans but may have their own distinctive chemistry of existence. "}],[{"start":null,"text":""}],[{"start":271.35,"text":"The cataloguing of exoplanets is part of a wider search for extraterrestrial intelligence, with radio telescopes also listening for signals from distant civilisations. Promising targets in the search for life include the worlds of the Trappist-1 system about 40 light years away. "}],[{"start":288.25,"text":"Some exoplanets are rocky and some are gassy. Some are hot enough to boil metal, others compare to Antarctica at its coldest. They may orbit two or more stars at once — or none at all. Their sizes are often benchmarked against the more familiar planets of our solar system, with names such as super-Earths and mini-Neptunes. "}],[{"start":311.35,"text":"The lessons from other planets can be profound, says Lisa Kaltenegger, director of the Carl Sagan Institute and an astronomy professor at Cornell University. "}],[{"start":321.40000000000003,"text":"She explains how the US scientist for whom her organisation is named was among the first to work out that Venus is extraordinarily hot. The reason: a runaway greenhouse effect created by an atmosphere composed mainly of carbon dioxide."}],[{"start":null,"text":""}],[{"start":336.95000000000005,"text":"Human knowledge of exoplanets is still fragmentary and imperfect. This has led to fierce debate over findings, notably over a world known as K2-18b that lies 124 light years from Earth. Scientists announced last year that it showed spectroscopic signs of biological activity, in what they called the strongest evidence yet of extraterrestrial life."}],[{"start":361.6,"text":"Further research on K2-18b has cast doubt on that claim. Other scientists said data suggesting the presence of dimethyl sulphide (DMS), a chemical produced by micro-organisms on Earth, was not statistically significant. Some experts argued that DMS might have been formed by non-life chemical processes, noting that it has previously been identified on a comet. "}],[{"start":384.55,"text":"The K2-18b dispute highlights how exoplanets are science’s furthest frontier. “We’re trying to figure out how those planets actually work on a fundamental level,” Kaltenegger says. "}],[{"start":null,"text":"

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"}],[{"start":395.2,"text":"Closer to home, aspirations for the Moon have broadened from occasional human visits to permanent occupancy. After 2028, Nasa aims to launch crewed lunar missions twice a year as it starts to prepare the infrastructure for a $20bn Moon base. Its nine candidate sites are all near the lunar south pole, where scientists believe most of the Moon’s water exists as ice shaded by crater walls."}],[{"start":419.84999999999997,"text":"Formidable obstacles lie ahead. Most importantly, the agency has not yet decided which — if either — of two competing landers supplied by Elon Musk’s SpaceX and Jeff Bezos’s Blue Origin will be ready in time to transport astronauts from the Orion spacecraft to the lunar surface for the Artemis IV mission in 2028. Next year the Artemis III mission will test the performance and docking abilities of both in Earth orbit. "}],[{"start":null,"text":""}],[{"start":446.79999999999995,"text":"The Trump administration is determined to lead the early settlement of the Moon but Nasa has emphasised collaboration, including with private sector companies such as the lander providers and space agencies in other countries. "}],[{"start":460.04999999999995,"text":"China is another matter. In echoes of the original space race between the US and USSR, Jared Isaacman, the Nasa administrator appointed by President Donald Trump in December, frequently cites competition with Beijing. He told the annual US Space Symposium in Colorado Springs last month: “American leadership in the high ground of space is not optional.”"}],[{"start":483.29999999999995,"text":"China has been sending increasingly ambitious robotic missions to the Moon for several years, including the first to land successfully on the far side in 2019 and return samples to Earth in 2024. "}],[{"start":497.34999999999997,"text":"Beijing aims to land a crew on the Moon by 2030. Many observers had expected it would target a landing site near the lunar south pole, as the US is doing. "}],[{"start":null,"text":""}],[{"start":507.29999999999995,"text":"But in March Chinese scientists published an analysis of the prospects for an area called Rimae Bode near the Moon’s equator. Its geology made it “a high-priority candidate for the upcoming Chinese crewed mission”, they said.  "}],[{"start":520.4499999999999,"text":"If China and the US head for different landing sites, it will reduce the chances of immediate territorial competition. "}],[{"start":527.4,"text":"But some observers fear an eventual conflict over lunar resources if it becomes profitable to mine the Moon for scarce substances to carry back to Earth. These include helium-3 for nuclear fusion reactors, or materials such as water for use on the Moon itself. "}],[{"start":544.6999999999999,"text":"“We do not want a frontier mentality and a lack of sustainable thinking to produce an interplanetary wild west,” says Mike Lockwood, president of the UK’s Royal Astronomical Society and a professor of space physics at the University of Reading. "}],[{"start":559.8499999999999,"text":"Additional revenue-raising activities include transport across the lunar surface, telecommunications and construction of habitation for visitors ranging from scientists to tourists. The Moon could also be a stepping stone to missions to Mars."}],[{"start":null,"text":"

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"}],[{"start":573.8499999999999,"text":"Robotics has opened new possibilities for space travel — and cast doubt on the need for humans to travel beyond Earth’s atmosphere at all."}],[{"start":581.8999999999999,"text":"For Martin Rees, former UK Astronomer Royal, “the practical case for human space flight gets ever weaker with each advance in robots”. "}],[{"start":590.3499999999999,"text":"“By the time the first crewed mission to Mars is ready to launch, rapid AI advances will surely close the current gap between robotic and human intellectual abilities,” he says."}],[{"start":600.6999999999999,"text":"There is the impact on the body of living in a low-gravity environment and the psychological toll of spending long periods in close contact with other astronauts. These hardships can be overcome, says Robin Wordsworth, professor of planetary science at Harvard University. “The challenge that will need most work is protecting against radiation from the sun and high-energy galactic cosmic rays from outer space,” he says."}],[{"start":624.2499999999999,"text":"A place that no human plans to go anytime soon is the cloudy and extremely acidic upper atmosphere of Venus. Nonetheless, researchers hope to find extraterrestrial life there. Temperatures hover around an equable 30C, in contrast to the lead-melting 460C on the planet’s surface. Traces of a gas called phosphine, associated with biological activity on Earth, were observed there in 2020. "}],[{"start":651.3999999999999,"text":"Sara Seager, a professor of planetary science at Massachusetts Institute of Technology, and her lab have shown that a wide range of organic molecules including potential building blocks of life could survive in the clouds’ concentrated sulphuric acid. She is now working with a private-public partnership to send probes to sample the atmosphere. "}],[{"start":null,"text":""}],[{"start":671.9499999999998,"text":"“I would estimate a 50:50 chance that there’s life in the Venus clouds,” says Seager. “For comparison, I would give a 75 per cent chance of life under the surface of Mars, though it is speculation at this stage.” "}],[{"start":684.1999999999998,"text":"Other potential havens for life are the liquid oceans believed to lie beneath the icy surface of some moons of Jupiter. This will be visited by the European Space Agency’s (ESA) Juice and Nasa’s Europa Clipper spacecraft in the early 2030s. "}],[{"start":699.5499999999998,"text":"ESA is also provisionally planning a mission called L4 to land on Saturn’s moon Enceladus in 2052 when it will be illuminated by the Sun. “I’ll be so old by then but we need a lot of time to deliver a mission that will carry out definitive experiments on the surface of Enceladus,” says Carole Mundell, ESA science director. “Exceptional claims require exceptional evidence.”"}],[{"start":723.8499999999998,"text":"The reactions to the images of Earth the Artemis astronauts sent back shows how outer space still captures public imagination, just as it did during the Apollo era. "}],[{"start":733.2499999999998,"text":"Even if AI-enabled robots outperform people on a practical level, manned missions will always have their place, says Wordsworth of Harvard. “There’s something about the experience of going to places we’ve never been before and stretching the boundaries of what’s possible that means human space exploration is going to continue,” he says. "}],[{"start":751.7499999999998,"text":"The discoveries about so many previously unknown worlds not only highlight underlying advances in technology and the great power competition that fuels them. They also show how suddenly and how fast humanity has made progress as it looks to the stars, the object of Plato’s interest millennia ago. "}],[{"start":771.7999999999997,"text":"As James Windsor, performance and payload manager for the mission named after the philosopher, says: “We’re trying to find, ideally, Earth 2.0.”"}],[{"start":787.7999999999997,"text":""}]],"url":"https://audio.ftcn.net.cn/album/a_1777614373_4566.mp3"}