Tag: Planetary science

China’s Chang’e-6 launches successfully — what happens next?

[ad_1]

Onboard this Long March 5 rocket, Chang’e-6 is waiting to lift off from the Wenchang Space Launch Centre on Hainan Island, southern China.Credit: Xinhua/Shutterstock

China has successfully launched its historic Chang’e-6 mission.The 53-day odyssey will be the most complex and challenging Moon mission China has carried out. If all goes according to plan, scientists will be examining the first rocks from the Moon’s far side by late June.

The 7.2-metre-tall, eight-tonne spacecraft lifted off aboard a Long March 5 rocket on Friday afternoon local time, piercing through a tropical rainstorm from the Wenchang Satellite Launch Centre on Hainan Island. Just over one hour into the flight, the China National Space Administration (CNSA) announced the launch “a complete success”, after the craft separated from the rocket and entered the designated Earth-Moon transfer orbit.

Quentin Parker, an astrophysicist at the University of Hong Kong, hails the launch as “flawless”. “China’s accomplishments in space exploration over the past few years are without precedent. If successful, this mission will be another science bonanza,” he says.

Two-faced Moon

The lunar far side, which always faces away from us because the Moon is tidally locked to Earth, could not be more different than its near side, says planetary scientist Bradley Jolliff at Washington University in St Louis. Most of the ancient volcanic activity on the Moon happened on the near side, while the far side remained quieter under a thick and heavily cratered crust. “You would hardly know that they are from the same body by comparing the two sides,” Jolliff says.

What China’s mission to collect rocks from the Moon’s far side could reveal

A total of 10 missions, manned or unmanned, have brought back Moon rocks for analysis — all from the near side. Landing on the Moon’s far side requires, among other things, a communications satellite to relay signals with Earth.

This is why China launched the Queqiao-2 satellite in March, which is equipped with a 4.2-metre-diameter radio antenna — the largest of its kind used in deep space exploration — to orbit the Moon and wait for the arrival of Chang’e-6.

After arriving at the Moon early this week, the spacecraft will gradually lower its orbit and prepare for landing in one of three pre-selected areas within the South Pole-Aitken basin (SPA). The SPA is the largest and oldest impact basin on the lunar surface, and samples from there will provide clues to the Moon’s two-face mystery and the early history of the solar system.

In early June, the spacecraft will drop a lander, which aims to drill and scoop up two kilograms of soil and rocks. Then an ascender will blast off from the lander and ferry the samples back to the orbiter for the trip back home. Thanks to Queqiao-2, the spacecraft and Earth will remain in contact during the mission’s critical moments, such as the 15-minute descent and touchdown, two-day sampling, and 6-minute ascent.

“The geological conditions on the far side are less clear. Whether we’ll actually be able to scoop up or drill down, all remains to be seen when the sampling begins,” Pei Zhaoyu, a senior CNSA official and chief designer of China’s upcoming Chang’e-8 mission, told China Central Television during the launch livestream.

Scientists hope Chang’e-6 will also return material from beyond its landing site, such as rock fragments thrown over to the landing site from far distant locations during powerful impacts, Jolliff says. The material collected at the Chang’e-6 site “will be like a treasure chest”, he says. “The samples collected will be analysed for decades to come, and hopefully with access provided to the international research community,” he says.

Chang’e-6 is expected to return to Earth around June 25. If successful, the precious samples will land at the Siziwang Banner Landing Site in Inner Mongolia and be retrieved within 48 hours, according to CNSA.

[ad_2]

Source link

May 6, 2024
what’s fact and what’s fiction?

[ad_1]

An alien civilization spying on humans using quantum entanglement. A planet chaotically orbiting three stars. Nanofibres capable of slicing through Earth’s hardest substance, diamond. Despite being chock-full of hardcore science, 3 Body Problem, a television series released on 21 March by the streaming service Netflix, has been a hit with audiences. So far, it has spent five weeks straight in Netflix’s list of the top-three programs viewed globally.

The science of Oppenheimer: meet the Oscar-winning movie’s specialist advisers

The story follows five young scientists who studied together at the University of Oxford, UK, as they grapple with mysterious deaths, particle-physics gone awry and aliens called the San-Ti who have their sights set on Earth. But how much of the science in the sci-fi epic, based on the award-winning book trilogy Remembrance of Earth’s Past by the Chinese writer Cixin Liu, reflects reality, and how much is wishful thinking? To find out, Nature spoke to three real-world scientists.

Xavier Dumusque is a planetary scientist at the University of Geneva in Switzerland who has studied the three-star system Alpha Centauri. Younan Xia is a materials scientist at the Georgia Institute of Technology in Atlanta who has worked with cutting-edge nanotechnologies. Matt Kenzie is a particle physicist at the University of Cambridge, UK — and was the scientific adviser for 3 Body Problem.

Kenzie originally met two of the show’s creators, David Benioff and D. B. Weiss, 14 years ago, while the pair were filming the popular fantasy saga Game of Thrones. Kenzie’s father was a director of photography for that series, and Benioff and Weiss chatted to Kenzie on set. “I was doing my PhD at the time,” Kenzie recalls, and they seemed interested in his thesis project. More than a decade later, “they e-mailed me sort of out of the blue, asking about some of the particle-physics stuff” in 3 Body Problem.

Full disclosure: spoilers ahead.

What do you think of the portrayal of scientists and their relationships in the series?

Kenzie: The lazy way of portraying scientists on screen [in other programs and films] is as lone geniuses. For a lot of modern research, it’s not like that. The fact that the characters all know each other and are very friendly because they did their PhDs together in the same group seems very plausible. I also think most physicists are socially very capable. We work in bigger and bigger teams. You need to be able to communicate, you need to be able to lead if you’re in a successful academic position, you have to be able to basically convince someone to fund your research, whether it’s by hiring you or by giving you funding.

Barbie and body image: a scholar’s take on the research — and the blockbuster film

One thing that’s probably not true to reality is that there are quite a few women — about half women — and a good mix of ethnic backgrounds in the actual cast of the show. The truth, sadly, is that [physics graduates] probably would be 70% white males at a place like Oxford. But, you know, we hope that that is improving. And I don’t think there’s any harm in the show trying to progress standards by displaying something a little bit more diverse.

Dumusque: Something that I liked, and it’s a little bit true, is that there are five former physics PhD students, and, in the end, there are only one or two that are still doing fundamental physics. All the others are doing other things — they are all successful. That’s the reality. I had ten close friends finishing PhDs, and now we are only two left in academia. The others are doing plenty of super-interesting things.

The San-Ti emerge from a planet in the three-body Alpha Centauri system. We’re told this means they’ve had a chaotic existence as their planet was flung between stars. Would aliens actually survive this?

Dumusque: Alpha Centauri is indeed a triple system, which has two bright stars, Alpha Centauri A and B, and a tiny star, Proxima Centauri, which is closest to us [at 1.3 parsecs away]. In fact, it was not clear for a long time if the third star, Proxima, was bound to the system — because it’s very, very far away, really at the limit of the system. The gravitational interaction of Proxima on the two main stars is extremely small. So what they’ve shown in the show — you have all this instability due to the third body — in reality, it doesn’t happen in this system.

There is a planet around Proxima, and it’s an interesting planet because the star is much smaller and cooler than our Sun. So although the planet is orbiting it with a period of just around 15 days, the surface temperature of the planet is more or less 0 °C. In terms of temperature, it could be habitable [although not comfortable]. But small stars like Proxima have a lot of magnetic activity and flares, and give out a lot of X-rays, all of which does not favour life.

The way Earth initially contacts the San-Ti is by amplifying a radio signal using the Sun. Is that possible?

Dumusque: I think it should be possible, but not in the way the 3 Body Problem shows. We can use the effect of gravitational lensing — if there is an object passing behind the Sun, we could use the mass of the Sun to amplify the [radio signal]. But it would be amplified just in one specific direction [rather than in all directions, as shown in the program].

The San-Ti, called Trisolarans in the books, unleash high-tech particles called sophons that use quantum entanglement to observe and communicate with Earth in real time. Is this feasible?

Kenzie: The mechanism shown has been proven, and I think will soon be deployed in what is known as quantum satellite technology. You’re basically sending signals incredibly fast using entangled particles, where, when you measure the state of one, you immediately know the state of the other. However, there is still a caveat to that, which is that you cannot communicate faster than the speed of light.

[To ‘read’ the distant particle] you still need to send an electromagnetic signal to decode the information [which travels at the speed of light]. Trisolarans circumvent this by knowing about hidden dimensions. They have a way of tunnelling through or exploiting those dimensions. So it appears like they’re communicating faster than light in our three- or four-dimensional Universe (if you include time as the fourth dimension).

Younan, you haven’t seen the series yet, but you’ve watched a clip in which nanofibres made by one character slice through a huge chunk of diamond as if it were cake. Are we there yet?

Xia: First, the size of the diamond you saw in that clip, that’s impossible! If you can make that size of a diamond, I’m sure you can easily become a billionaire. As far as I know, no material has been made that’s harder than diamond. Scientists have dreamt about finding a material to beat diamond for decades. They have even identified some compounds, like [a particular type of] carbon nitride, using computer simulations, that could work, but these materials cannot be synthesized in the lab. Maybe there are some formulations of compounds that would work, materials we just don’t know of yet.

People have also thought a carbon nanotube could be stronger than diamond. But that kind of strength is a ‘stretching’ strength and is not really suitable for cutting applications. Carbon nanotubes are rolled up sheets of graphene. But most of them are pretty short in terms of length. So far, it’s been difficult to make them even a few centimetres long without defects; I don’t know how they could’ve made these fibres [in the program].

Matt, as the scientific adviser, were you happy with how the series turned out?

Kenzie: The writers of this show really know a lot about science. They’re very well read, and they think about things very carefully. They’re not just asking [me for advice] to make themselves feel better, they really think about things. The level of attention to detail that they showed was something that impressed me. I was not really expecting it, to be honest.

[ad_2]

Source link

April 30, 2024
What China’s mission to collect rocks from the far side could reveal about the Moon

[ad_1]

Later this week, China will embark on the world’s second-only trip to the Moon’s far side. The goal is to collect the first rocks from inside the South Pole-Aitken (SPA) basin, the largest and oldest impact crater on the lunar surface, and bring them back to Earth for analysis.

A stack of four spacecraft needed to complete this unprecedented and highly challenging mission, known as Chang’e-6, is now tucked into the nose of a 57-metre-tall Long March 5 rocket, waiting to lift off from the Wenchang Satellite Launch Centre on southern China’s Hainan Island.

“The whole process is very complex and risky,” says Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.

But he says it’s a risk worth taking: “Samples from the SPA basin would be very interesting scientifically and tell us a lot about the history of the Moon and of the early Solar System.”

Far side science

Because the Moon is tidally locked to Earth, humans were only able to see its near side for thousands of years. In 1959, the first lunar far-side images returned by the Soviet probe Luna 3 revealed a face pocked with mountains and impact craters, in contrast to the relatively smooth near side. Scientists have since been collecting data from satellites orbiting the Moon to understand its little-known other half. In 2019, China’s Chang’e-4 became the first spacecraft to soft land and conduct surveys on the Moon’s far side.

The upcoming Chang’e-6 mission, with its landing site carefully chosen by Chinese scientists and international colleagues, aims to give the first accurate measurements of the age and composition of the geology of the Moon’s far side. It might provide key clues to why the two sides of the Moon are so different — the so-called lunar dichotomy mystery — and help test theories about the early history of the Solar System.

The SPA Basin is a vast indentation on the lower half of the far side some 2,500 kilometres wide and 8 kilometres deep. Inside the northeastern part, Li’s team has identified three potential landing areas. They believe the sites could have a variety of materials formed during repeated asteroid impacts and volcanic eruptions over two billion years, and therefore could be scientifically rich.

The South Pole-Aitken Basin is the blue area in the centre of this false-colour image. The indentation is 2,500 kilometres wide.Credit: NASA/GSFC/University Of Arizona

The most likely rock to be collected is basalt — dark-coloured cooled lava — which has previously been brought back to Earth for analysis from the Moon’s near side. With the first far-side basalt samples, scientists will be able to date them and assess their chemical composition, giving clues to their formation. “Then we can make comparative studies to understand why volcanic activities happened on a much smaller scale and ended much earlier on the far side of the Moon,” says Long Xiao, a planetary scientist at the China University of Geosciences in Wuhan.

Being able to pin down the SPA Basin’s age would also be a major achievement, says planetary geologist Carolyn van der Bogert from the University of Münster, Germany. It will help settle the long-standing debate about whether the Moon and the inner Solar System was battered by a massive cluster of asteroids between 4.0 and 3.8 billion years ago. If the SPA Basin is older, then it would cast doubt on the heavy bombardment theory.

Besides basalts, scientists hope that Chang’e-6 will also pick up fragments of other rocks that have been scattered during impact events. If the Chinese mission strikes ejecta the from the deeper lunar crust or mantle, it will be scientific gold.

Engineering challenges

Chang’e-6 was originally built as a backup for the Chang’e-5 mission, which successfully returned 1.73 kilograms of samples from the Moon’s near side in 2020. Because the two craft are identical, site selection for Chang’e-6’s landing was constrained to similar latitudes as Chang’e-5’s and needed a relatively flat surface, says Chunlai Li, the mission’s deputy chief designer from the National Astronomical Observatories in Beijing.

Like its predecessor, Chang’e-6 does not pre-determine its landing site but will use its instrumentation during the descent process to find the safest and most favourable spot. “The landing of Chang’e-6 would be more challenging than Chang’e-5 simply because the far side landing site is more rugged,” says Xiao.

Chang’e-6, like its twin, consists of an orbiter, a lander, an ascender and a re-entry module. When the spacecraft arrives at the Moon, it will separate into two parts, with the lander and ascender headed for the lunar surface while the orbiter and re-entry module remain in orbit.

If it pulls off the difficult soft landing, the lander will drill and scoop up two kilograms of soil and rocks. The sampling process needs to be completed within 48 hours, after which the ascender is intended to blast off from the lander and return to the lunar orbiter. There it is supposed to dock and transfer the precious samples to the re-entry module for the trip home.

During the sample collection and lunar surface liftoff, the Chang’e-6 lander would be unable to directly communicate with Earth. Every command will need to go through a relay satellite named Queqiao-2. Launched last month and now operating in a highly elliptical orbit around the Moon, Queqiao-2 is more powerful than the Queqiao satellite which served the Chang’e-4 mission. Its 4.2-metre umbrella-shaped antenna has the ability to simultaneously serve up to ten spacecraft working on the Moon’s far side.

International collaboration

Chang’e-6 is also carrying scientific payloads from France, Sweden, Italy and Pakistan. The Detection of Outgassing RadoN (DORN), which will be the first French instrument on the Moon, plans to use radon released from the lunar surface as a tracer to study the origin and dynamics of the Moon’s faint atmosphere. Pierre-Yves Meslin, a planetary scientist at the Research Institute in Astrophysics and Planetology in Toulouse, France, says previous spacecraft have measured radon gas movement from orbit, but surface-level radon information is the missing piece of the puzzle.

The Negative Ions at the Lunar Surface, a payload developed in Sweden with funding from the European Space Agency, will seek to answer the question of why no negative ions have yet been detected on the lunar surface. Negative particles could be short-lived, formed either by atoms at the surface snatching electrons from the solar wind, or by molecules breaking apart from the high-energy solar radiation. The biggest challenge for this instrument is overheating, since it needs to face the Sun, says ESA project manager Neil Melville. But he says one hour of operation should be enough to gather the data.

Italy’s National Institute of Nuclear Physics is sending a laser retroreflector for distance measurements. And Pakistan has piggy-backed its first lunar satellite to the Chang’e 6 orbiter, which will deploy after entering the lunar orbit.

Both surface instruments need to complete their work and send data back to Earth within the 48-hour window. “As soon as the samples lift off, the ascender will bring with it the communications and control system it shares with the lander. Even if the instruments on the lander continue to take data, there is no way to receive them here on Earth,” Li says

He says that like Chang’e-5 samples, the returned Chang’e-6 samples will be shared with the international community.

“When those samples come back to Earth, they will be like a Christmas present — whoever opens it will be happily surprised,” Bogert says.

[ad_2]

Source link

April 30, 2024
China’s Moon atlas is the most detailed ever made

[ad_1]

The Chinese Academy of Sciences (CAS) has released the highest-resolution geological maps of the Moon yet. The Geologic Atlas of the Lunar Globe, which took more than 100 researchers over a decade to compile, reveals a total of 12,341 craters, 81 basins and 17 rock types, along with other basic geological information about the lunar surface. The maps were made at the unprecedented scale of 1:2,500,000.

“Every question in geology starts with looking at a geological map,” says Ross Mitchell, a geophysicist at the CAS Institute of Geology and Geophysics in Beijing. The new lunar atlas is “really a resource for the whole world”, he says.

The CAS also released a book called Map Quadrangles of the Geologic Atlas of the Moon, comprising 30 sector diagrams which together form a visualization of the whole Moon.

Jianzhong Liu, a geochemist at the CAS Institute of Geochemistry in Guiyang and co-leader of the project, says that existing Moon maps date from the 1960s and 1970s. “The US Geological Survey used data from the Apollo missions to create a number of geological maps of the Moon, including a global map at the scale of 1:5,000,000 and some regional, higher-accuracy ones near the landing sites,” he says. “Since then, our knowledge of the Moon has advanced greatly, and those maps could no longer meet the needs for future lunar research and exploration.”

China will use the maps to support its lunar ambitions and Liu says that the maps will be beneficial to other countries as they undertake their own Moon missions. Three spacecraft have launched aiming for the Moon so far this year, and in May, China intends to send a craft to collect rocks from the Moon’s far side.

Scientists will use the new lunar maps to better understand the Moon’s history.Credit: Chinese Academy of Sciences via Xinhua/Alamy

With the updated atlas, scientists will be able to better understand the history of the Moon, evaluate potential lunar resources and conduct comparative geological studies. It will also inform the location choices of future missions including where to build a lunar research base, Liu says.

Carolyn van der Bogert, a planetary geologist at the University of Münster in Germany, says she was impressed by the amount of work that Chinese colleagues have put into compiling the new atlas.

“We are looking forward to being able to interact with the map in a very detailed way,” she says.

Other-worldly cartography

The atlas, which is available in both Chinese and English, was assembled using data from China’s lunar exploration programme, especially the Chang’e-1 mission, which surveyed the lunar surface from orbit between 2007 and 2009, according to Liu. “Chang’e-1’s camera conducted observation of lunar topography and geological structures, while its interference imaging spectrometer played a key role in identifying different rock types,” he says.

The new atlas was assembled using data from China’s lunar exploration programme.Credit: Chinese Academy of Sciences via Xinhua/Alamy

Observations made on the Moon’s surface by the Chang’e-3 and Chang’e-4 lander missions in 2013 and 2019, respectively, helped to verify the accuracy of the Chang’e-1 data. The atlas team also used data from missions such as the Gravity Recovery and Interior Laboratory (GRAIL) and the Lunar Reconnaissance Orbiter, both launched by NASA, and India’s Chandrayaan-1 probe. “Some observations were highly complementary to the Chang’e missions. For instance, GRAIL’s data helped us identify all the deep fractures on the lunar surface,” Liu says.

Chinese researchers started to compile the maps in 2012 as they were searching for the next targets to explore on the Moon. In partnership with Russia and more than a dozen other countries and organizations, China is leading the construction of the International Lunar Research Station, which is intended to take shape in the mid-2030s at the Moon’s south pole for scientific exploration and resource exploitation.

“Contributing to lunar science is a profound way for China to assert its potential role as a scientific powerhouse in the decades to come,” says Mitchell.

Liu says that his team has already started work to improve the resolution of the maps, and will produce regional maps of higher accuracy on the basis of scientific and engineering needs. In the meantime, the completed atlas has been integrated into a cloud platform called the Digital Moon, and will eventually become available to the international research community.

[ad_2]

Source link

April 25, 2024
How gliding marsupials got their ‘wings’

[ad_1]

Download the Nature Podcast 24 April 2024

In this episode:

00:46 Optical clocks at sea

Optical atomic clocks are the most precise timekeeping devices on the planet, but these devices are huge and difficult to work with, limiting their use outside of the lab. Now, researchers have developed a portable optical clock and demonstrated its robustness by sending it on a perilous sea journey. The team hope that this work will pave the way to more practical uses of optical clocks, such as on satellites where they could help improve the accuracy of GPS technologies.

Research Article: Roslund et al.

News and Views: Robust optical clocks promise stable timing in a portable package

09:34 Research Highlights

Evidence of ritual burning of the remains of a Maya royal family, and the first solid detection of an astrophysical tau-neutrino.

Research Highlight: Burnt remains of Maya royalty mark a dramatic power shift

Research Highlight: Detectors deep in South Pole ice pin down elusive tau neutrino

11:52 How marsupial gliding membranes evolved

Several marsupial species have evolved a membrane called a patagium that allows them to glide gracefully from tree to tree. Experiments show that mutations in areas of DNA around the gene Emx2 were key to the evolution of this ability, which has appeared independently in multiple marsupial species.

Research article: Moreno et al.

News and Views: Marsupial genomes reveal how a skin membrane for gliding evolved

19:22 Briefing Chat

How overtraining AIs can help them discover novel solutions, and researchers manage to make one-atom thick sheets of ‘goldene’.

Quanta Magazine: How Do Machines ‘Grok’ Data?

Nature news: Meet ‘goldene’: this gilded cousin of graphene is also one atom thick

Subscribe to Nature Briefing, an unmissable daily round-up of science news, opinion and analysis free in your inbox every weekday.

Subscribe to Nature Briefing: AI and robotics

Never miss an episode. Subscribe to the Nature Podcast on Apple Podcasts, Spotify, YouTube Music or your favourite podcast app. An RSS feed for the Nature Podcast is available too.

[ad_2]

Source link

April 24, 2024
Violent volcanoes have wracked Jupiter’s moon Io for billions of years

[ad_1]

Jupiter’s moon Io has been continuously shaped by volcanic activity for billions of years — possibly even for the Solar System’s entire 4.57-billion-year history, a study suggests.

The findings, published in Science on 18 April¹, have implications for the search for extraterrestrial life and for the understanding of volcanic moons and planets, including Earth.

Io is the most volcanically active place in the Solar System, with hundreds of volcanoes on its surface. This makes it difficult to study the moon’s past. The moon is continuously resurfaced by the constant flow of runny lava and ash settling from volcanic plumes, obscuring any physical evidence of its history. The volcanic activity arises because Io’s orbit of Jupiter is synchronized with the orbits of two neighbouring moons, Europa and Ganymede. The gravitational interactions between them make Io’s orbit elliptical and periodically squeeze the moon’s centre, causing friction and heating.

Sulfur studies

When Io’s volcanoes erupt, they spew sulfur-rich gases into the atmosphere. The researchers were able to use this sulfur as “a tracer for studying Io’s long-term evolution”, explains Katherine de Kleer, a planetary scientist at the California Institute of Technology in Pasadena and a co-author of the study.

Throughout the Solar System, the ratio between two sulfur isotopes — sulfur-32 and the slightly heavier sulfur-34 — is relatively constant, says de Kleer. Using the Atacama Large Millimeter/submillimeter Array, a radio telescope in Chile, she and her and colleagues measured sulfur emissions in Io’s atmosphere and calculated the ratio between the two isotopes.

Their observations revealed that Io has lost 94–99% of its originally available sulfur. At the top of its atmosphere, the ratio of sulfur isotopes is slightly skewed towards the lighter variant, and these gases rich in sulfur-32 are “being stripped off the top of the atmosphere at a loss of about one tonne per second”, de Kleer says. Over billions of years, this discrepancy has accumulated, and Io’s overall sulfur composition has become heavier. By extrapolating from the current rate at which the lighter sulfur is being lost, the researchers calculated that Io’s volcanoes have been erupting for most of its history.

Implications for Europa

The research also validates models that suggest Io, Europa and Ganymede have been caught in the same orbital dance since the birth of the Solar System, or soon afterwards. This raises the possibility that Europa has been experiencing similar heating for a similar amount of time, says de Kleer. Europa is a promising candidate for a place in the Solar System that has the potential to harbour life. Billions of years of heating “would enhance the habitability of Europa’s subsurface ocean over the long term”.

The very hot, runny lava on Io is much hotter than what found on Earth now, “but it’s thought to be the composition of magma that dominated in Earth’s early history, when we had these huge events laying down big regions of lava flows in a short period of time”, says de Kleer. “Io’s volcanism might be giving us a window into the mechanisms of volcanism and Earth’s early history.”

Jani Radebaugh, a planetary geologist at Brigham Young University in Provo, Utah, welcomes the findings. “That Io could be even more exciting — even more extreme — in its volcanism is mind-blowing,” she says. “The results reveal that further exploration of Io would help us uncover the unknown histories of other volcanic worlds, including our own planet.”

[ad_2]

Source link

April 18, 2024
NASA admits plan to bring Mars rocks to Earth won’t work — and seeks fresh ideas

[ad_1]

NASA’s Perseverance rover collects a sample from a Martian rock using a bit on the end of its robotic arm.Credit: NASA/JPL-Caltech

NASA announced today that it is abandoning its longstanding plan for ferrying rock and soil samples from Mars to Earth. Instead the agency will seek proposals for quicker and cheaper ways to deliver the samples to Earth.

An independent review board concluded last year that NASA’s Mars sample return mission could cost as much as US$11 billion, more than what it cost to launch the James Webb Space Telescope. In a report released today, a separate NASA review team concluded that even if the agency spent that much money, the dropoff of the samples on Earth would be delayed until 2040. The agency had originally sought to land the samples on Earth in the early 2030s.

The $11 billion price tag is “too expensive,” said NASA administrator Bill Nelson at a press briefing, and “not returning the samples until 2040 is unacceptable.” Nelson said the agency “is committed to bringing at least some of the samples back” and later said NASA would return “more than 30” of the 43 planned samples.

Scaling back

NASA’s Perseverance rover has already collected more than 20 rock samples from Jezero Crater, where the rover landed in 2020. Scientists think that the crater was once filled with a lake of water, and samples from the crater and its surroundings could provide a window into the planet’s history and, perhaps, evidence of past life on the red planet.

In the agency’s original vision, a NASA spacecraft would have flown to Mars carrying a two-part retrieval system: a half-ton lander — which would have been the most massive vehicle to ever land on Mars — and a rocket to fly the lander and samples into Martian orbit. There they were to meet a spacecraft launched by the European Space Agency that would fly the samples to Earth.

Now NASA plans to solicit proposals — from companies as well as NASA centres — for a streamlined system, perhaps one that uses a lighter lander, Nicky Fox, the associate administrator for NASA’s Science Mission Directorate, said at the briefing. The deadline for proposals is 17 May, and the revised mission will be chosen later this year. Fox did not respond directly to reporters’ questions about when the samples will reach Earth under the new scheme.

NASA recommends spending $200 million of its planetary-science budget in 2025 on assessing alternative architectures for Mars sample return, Fox said. Dedicating any more money to the mission threatened to “cannibalize” other planetary science missions, Nelson said.

Back to the drawing board

Vicky Hamilton, a planetary scientist at the Southwest Research Institute in Boulder, Colorado, expressed disappointment that eight months after the independent review board released its report, the agency still lacks a solid plan for “a very valuable science goal.”

Returning these samples would also demonstrate capability for two-way trip to Mars before we can send astronauts, says Bethany Ehlmann, a planetary scientist at the California Institute of Technology in Pasadena, California. “The sample return technology is here, it exists,” she says. “It’s a matter of putting the pieces together.”

But scientists were relieved by one announcement: Fox said the revised timeline for sample return will not affect the science goals for Perseverance, including plans for it to explore terrain beyond Jezero Crater.

NASA’s Mars rover makes ‘fantastic’ find in search for past life

Among samples collected outside the crater will be “some of the ancient crust of Mars, representing rocks older than we have seen yet in Jezero Crater, some of which may have been altered by near-surface water,” says Meenakshi Wadhwa, a planetary scientist at Arizona State University in Tempe and principal scientist for the Mars Sample Return program.

So far, the only Mars samples that scientists have been able to study on Earth are bits and pieces ejected from the red planet that made it to Earth as meteorites. All known Martian meteorites are “igneous” rocks, meaning that they solidified from lava, and all are very old. As a result, they provide valuable timestamps for Mars’ geological evolution, but carry little information about how the planet’s surface was shaped by the water that once flowed across it.

To achieve the mission’s main goal of searching for signs of past life, the real treasures are layered sedimentary rocks formed by minerals and organic matter deposited over the aeons by water. Perseverance’s instruments have already detected organic molecules in Martian samples, but whether those molecules are a marker of past life can only be determined by closer scrutiny in laboratories on Earth.

[ad_2]

Source link

April 15, 2024
This super-Earth is the first planet confirmed to have a permanent dark side

[ad_1]

One side of the planet LHS 3844b (artist’s impression) is thought to be in perpetual daylight.Credit: NASA/JPL-Caltech/R. Hurt (IPAC)

Imagine if it were always night-time in the Western Hemisphere and always daytime in the Eastern Hemisphere, and the only way for Londoners to see the Sun was to fly to somewhere like Tokyo.

In a study published today in The Astrophysical Journal, scientists provide the most compelling evidence to date that a planet has this feature¹, called tidal synchronization or 1:1 tidal locking. Astronomers think that many exoplanets are similarly ‘stuck’ — including most of the candidates with potential to sustain life.

“This thing that has been theoretical now feels real. This is actually what these planets look like,” says Nicolas Cowan, an astronomer at McGill University in Montreal, Canada, and a co-author of the study.

Two sides of the story

When a planet orbits very close to its star, its near side experiences a much stronger pull than its far side does. Over time, the imbalance, called a tidal force, is thought to slow the planet’s rotation until it is in perfect synchrony with its orbit. This means that the time taken for the planet to rotate once on its axis is the same as that needed for it to travel once around its star. The Moon is thought to have undergone this process, which explains why it has a ‘far side’ that never faces Earth.

Many exoplanets are thought to be 1:1 tidally locked on account of their close proximity to their host star, but that status is difficult to prove. Measuring an exoplanet’s orbit is straightforward; pinning down its rotation is much harder, especially if the planet has an atmosphere that obscures its spinning surface from view.

JWST gets best view yet of planet in hotly pursued star system

The scientists turned to a particular exoplanet that is close to its star to finally prove the tidal locking hypothesis. In 2019, researchers using the Spitzer Space Telescope measured the intensity of light coming off this planet², called super-Earth LHS 3844b. Cowan and his co-authors realized that these measurements could tell them the temperature of the planet’s Earth-facing surface, because the planet probably has no atmosphere.

Planets that are not tidally synchronized heat up as a result of the conflict between their rotation and the massive tidal force exerted by their star. The team found the surface of LHS 3844b to be relatively cool — as would be expected for a tidally synchronized planet.

Compelling case

“This is the most compelling evidence one could possibly gather with currently existing information or instrumentation,” says Emily Rauscher, a theoretical astrophysicist at the University of Michigan in Ann Arbor.

Astronomer Emily Whittaker at the University of California, Los Angeles, notes that the paper assumes LHS 3844b has no atmosphere, but that a 2022 study which they co-authored left room for a thin, Earth-like atmosphere³. They say this could complicate the new paper’s argument, but agree that the evidence the team has laid out does point to tidal synchronization.

More evidence is expected soon. “James Webb is great for this,” says Cowan. The James Webb Space Telescope (JWST) will allow astronomers to study the rotation of exoplanets orbiting slightly further from their stars than LHS 3844b does. Astronomers now think that such planets, which can sustain an atmosphere and mild temperatures, constitute most of the Milky Way’s habitable real estate. If the JWST finds them to be tidally synchronized like LHS 3844b, Cowan says, then “probably a good fraction of planets, certainly most habitable planets, are tidally locked”.

As for in what sense such planets could be habitable, Cowan can’t currently speculate. These worlds “don’t have tides, or seasons or day–night cycles”, he says. “Could you get the same kind of diversity and complexity of life evolving? I have no idea.”

[ad_2]

Source link

March 28, 2024
Planet-eating stars hint at hidden chaos in the Milky Way

[ad_1]

A star in the process of consuming a planet (artist’s conception).Credit: NG Images/Alamy

Stellar detectives have identified seven stars that recently dined on a rocky planet. The study doubles the number of binary stars known to have consumed a planet, and questions the perception that mature solar systems harbouring Earth-like planets are usually stable.

The findings, published in Nature on 20 March¹, show “strong evidence of planet ingestion”, says Jianrong Shi, an astronomer at the National Astronomical Observatories in Beijing. The planets seem to have been eaten during their stars’ relatively stable main-sequence period, adds study co-author Fan Liu, an astronomer at Monash University in Melbourne, Australia.

If this is true, it means these systems have continued to be chaotic long after their formation, with planets disintegrating or falling into their star, says Johanna Teske, an astronomer at the Carnegie Institution for Science in Washington DC. “It’s an inference at this point. We need to look at these systems in more detail,” she says.

Swallowed by stars

Last year, for the first time, astronomers observed a star in the process of eating a planet. But unravelling whether a star has done so in the past is challenging, because planets are tiny compared with their hosts, and their contents soon get diluted.

Different elements absorb and emit light of different wavelengths, so the composition of a star’s surface leaves a fingerprint on the light reaching Earth. But detecting whether a star has eaten a planet is similar to spotting a chocolate chip that’s been swirled into a bowl of vanilla ice cream, says Teske. Stars also vary a lot in their make-up, making it tough to prove that a star has a particular composition because it ingested a planet.

The 2,000 stars where aliens would catch a glimpse of Earth

To hunt for planet-eating stars, Liu and his colleagues performed a cosmic-twin study. Using the Gaia space telescope, they found 91 pairs of Sun-like stars nearby in the Milky Way, whose motions suggested that they were both born in the same gas cloud. The stars in such paired systems should have near-identical compositions and their similar lives should rule out many potential causes for discrepancies.

The team then used three ground-based telescopes to study the abundance of 21 elements in the pairs. If there were notable differences between a pair of stars, the researchers looked at whether this could be explained through noise in the data or other sources of variation. For seven pairs, “the difference has to be explained by one [star] ingesting a planet and the other not”, says Meridith Joyce, an astrophysicist at the Konkoly Observatory in Budapest, and a co-author on the paper.

Secret planet-eaters

The study suggests that around 8% of Sun-like star pairs in our region of the Milky Way harbour a planet-eater, says Liu. He adds that this estimate is conservative, because the team considered only stars ingesting rocky planets, whereas other stars might have eaten gaseous Jupiter- or Neptune-like bodies. The method would also have missed cases in which both stars had eaten a planet of similar composition.

Finding clear signs of planet ingestion in billion-year-old stars is “something unexpected”, he says. Astronomers often consider planet-eating to be a feature of a star’s early life, when planetary orbits are unstable and collisions are probable. But these meals must have been relatively recent, in the last few hundred millions of years, or theory suggests the evidence would’ve been undetectable, says Liu. The planets could have met their fate when their eroding atmospheres caused them to spiral inward, or some stars might have captured untethered rogue planets as they flew by, he adds.

Shi says that astronomers should examine these systems to see if any sibling exoplanets remain. The findings should make Earth-dwellers grateful, he says. The diversity of exoplanets has continued to shock astronomers; now it seems that “our Solar System is not only unique, but also undoubtedly peaceful”.

[ad_2]

Source link

March 20, 2024
Climate models can’t explain 2023’s huge heat anomaly — we could be in uncharted territory

[ad_1]

When I took over as the director of NASA’s Goddard Institute for Space Studies, I inherited a project that tracks temperature changes since 1880. Using this trove of data, I’ve made climate predictions at the start of every year since 2016. It’s humbling, and a bit worrying, to admit that no year has confounded climate scientists’ predictive capabilities more than 2023 has.

For the past nine months, mean land and sea surface temperatures have overshot previous records each month by up to 0.2 °C — a huge margin at the planetary scale. A general warming trend is expected because of rising greenhouse-gas emissions, but this sudden heat spike greatly exceeds predictions made by statistical climate models that rely on past observations. Many reasons for this discrepancy have been proposed but, as yet, no combination of them has been able to reconcile our theories with what has happened.

Earth just had its hottest year on record — climate change is to blame

For a start, prevalent global climate conditions one year ago would have suggested that a spell of record-setting warmth was unlikely. Early last year, the tropical Pacific Ocean was coming out of a three-year period of La Niña, a climate phenomenon associated with the relative cooling of the central and eastern Pacific Ocean. Drawing on precedents when similar conditions prevailed at the beginning of a year, several climate scientists, including me, put the odds of 2023 turning out to be a record warm year at just one in five.

El Niño — the inverse of La Niña — causes the eastern tropical Pacific Ocean to warm up. This weather pattern set in only in the second half of the year, and the current spell is milder than similar events in 1997–98 and 2015–16.

However, starting last March, sea surface temperatures in the North Atlantic Ocean began to shoot up. By June, the extent of sea ice around Antarctica was by far the lowest on record. Compared with the average ice cover between 1981 and 2010, a patch of sea ice roughly the size of Alaska was missing. The observed temperature anomaly has not only been much larger than expected, but also started showing up several months before the onset of El Niño.

The climate disaster strikes: what the data say

So, what might have caused this heat spike? Atmospheric greenhouse-gas levels have continued to rise, but the extra load since 2022 can account for further warming of only about 0.02 °C. Other theories put forward by climate scientists include fallout from the January 2022 Hunga Tonga–Hunga Ha‘apai volcanic eruption in Tonga, which had both cooling effects from aerosols and warming ones from stratospheric water vapour, and the ramping up of solar activity in the run-up to a predicted solar maximum. But these factors explain, at most, a few hundredths of a degree in warming (Schoeberl, M. R. et al. Geophys. Res. Lett. 50, e2023GL104634; 2023). Even after taking all plausible explanations into account, the divergence between expected and observed annual mean temperatures in 2023 remains about 0.2 °C — roughly the gap between the previous and current annual record.

There is one more factor that could be playing a part. In 2020, new regulations required the shipping industry to use cleaner fuels that reduce sulfur emissions. Sulfur compounds in the atmosphere are reflective and influence several properties of clouds, thereby having an overall cooling effect. Preliminary estimates of the impact of these rules show a negligible effect on global mean temperatures — a change of only a few hundredths of a degree. But reliable assessments of aerosol emissions rely on networks of mostly volunteer-driven efforts, and it could be a year or more before the full data from 2023 are available.

With the arrival of El Niño, prepare for stronger marine heatwaves

This is too long a wait. Better, more nimble data-collection systems are clearly needed. NASA’s PACE mission, which launched in February, is a step in the right direction. In a few months, the satellite should start providing a global assessment of the composition of various aerosol particles in the atmosphere. The data will be invaluable for reducing the substantial aerosol-related uncertainty in climate models. Hindcasts, informed by new data, could also provide insights into last year’s climate events.

But it seems unlikely that aerosol effects provide anything close to a full answer. In general, the 2023 temperature anomaly has come out of the blue, revealing an unprecedented knowledge gap perhaps for the first time since about 40 years ago, when satellite data began offering modellers an unparalleled, real-time view of Earth’s climate system. If the anomaly does not stabilize by August — a reasonable expectation based on previous El Niño events — then the world will be in uncharted territory. It could imply that a warming planet is already fundamentally altering how the climate system operates, much sooner than scientists had anticipated. It could also mean that statistical inferences based on past events are less reliable than we thought, adding more uncertainty to seasonal predictions of droughts and rainfall patterns.

Much of the world’s climate is driven by intricate, long-distance links — known as teleconnections — fuelled by sea and atmospheric currents. If their behaviour is in flux or markedly diverging from previous observations, we need to know about such changes in real time. We need answers for why 2023 turned out to be the warmest year in possibly the past 100,000 years. And we need them quickly.

Competing Interests

The author declares no competing interests.

[ad_2]

Source link

March 19, 2024