Enlarge/ Artist’s view of the configuration of Ariane 6 using four boosters on the ELA-4 launch pad together with its mobile gantry.
ESA-D. Ducros
There is “no guarantee” France’s ArianeGroup will continue to be Europe’s rocket launch company of choice, according to the head of the European Space Agency, after ESA member states agreed to introduce more competition to the market.
Josef Aschbacher, the agency’s director-general, told the Financial Times that the decision at its space summit in Seville last November to open the European launcher market to competition was a “game-changer.”
The next generation of launch would be done “in a very different way,” he said, acknowledging that this would put pressure on ArianeGroup’s owners, Airbus and Safran. “If they have a very competitive launcher, then they are in the race. But there is no guarantee.”
Martin Sion, chief executive of ArianeGroup, which since 2017 has lost its dominance of the commercial launch market to Elon Musk’s SpaceX, said the company was ready for the challenge. “The rules are changing, we will adapt,” he said. “We are used to competition.”
However, Aschbacher’s comments, made in an interview late last year, are a clear warning to ArianeGroup, which has suffered serial delays on its latest launcher, Ariane 6, now expected to be four years late.
As a result of the delays, and problems with the smaller Vega-C, which is manufactured by Italy’s Avio, Europe has had to use SpaceX to send some of its most important satellites into orbit.
In November, France, Germany, and Italy agreed to inject new funds into the Ariane 6 program, but the rocket is not reusable and will still be more expensive than SpaceX’s workhorse Falcon 9 when it finally launches around the middle of the year.
Guillaume Faury, Airbus chief executive, said in a separate interview that competition posed a serious challenge to ArianeGroup. “As one of the two shareholders, we are worried, as Ariane is today the incumbent,” he said. “The way to take our share is to make sure Ariane 6 will be a success.”
He acknowledged that Europe needed to find a more “market-driven” way to compete with lower-cost providers such as SpaceX but suggested it should not give up on Ariane in favor of a range of competing programs. Fragmentation would be “a disaster,” he said.
If the “result [of competition] is a different way being united around a small number of programs, where states put their efforts together to compete against the real competitors, which are . . . mainly SpaceX and the Chinese to come, that is OK,” he told the FT. “But the jury is out. For the moment what we observe is further fragmentation.”
Yet the ESA is determined to shake up the European commercial space sector by emulating the approach of NASA. Over the past two decades, the US space agency has shifted from buying rockets from incumbents such as Boeing and Lockheed’s United Launch Alliance to booking flight services.
By giving contracts to disruptive newcomers such as SpaceX, NASA has ensured the success of Elon Musk’s rocket company, and the cost of launching into space has fallen significantly.
“Competition is certainly the solution. It is a way of reducing cost and this is what we are planning to do in the next generation,” Aschbacher said. ESA has also challenged the private sector to develop a cargo vehicle that might eventually carry crew to the International Space Station by 2028, reducing its reliance on US providers.
Germany in particular is keen on more competition in the launcher market, as the home of some of Europe’s most advanced rocket start-ups such as Isar Aerospace and Rocket Factory Augsburg.
Although ArianeGroup was currently Europe’s only producer of heavy lift rockets, it was possible that new rivals could upset its monopoly for the generation after Ariane 6, said Caleb Henry, director of research at consultancy Quilty Space.
SpaceX “had a smaller rocket and reached space. That was enough to get . . . a significant chunk of the Department of Defense market,” he said. “So it is not at all a stretch to say someone developing a smaller rocket today could be making an Ariane-sized rocket tomorrow.”
Enlarge/ Astrobotic’s Peregrine lander is seen recently encapsulated inside the Vulcan rocket’s payload fairing.
On Monday morning, the new Vulcan rocket made a smashing debut, launching from Cape Canaveral Space Force Station in Florida and performing flawlessly. After 50 minutes of flight, the rocket’s upper stage deployed its primary payload—the Peregrine lunar lander—into a Moon-bound trajectory. United Launch Alliance declared complete success with its new rocket.
After the deployment of the spacecraft, its developer, Pittsburgh-based Astrobotic, also said its ground controllers had successfully established contact with Peregrine. All seemed well as the spacecraft entered a highly elliptical orbit that will bring it toward the Moon in the coming weeks.
However, later on Monday morning, about six hours after liftoff, Astrobotic released an updated statement. While the vehicle’s avionics systems, including the primary command and data handling unit and the thermal, propulsion, and power controllers, had all powered on and performed as expected, there was a problem.
“After successful propulsion systems activation, Peregrine entered a safe operational state,” the company said. “Unfortunately, an anomaly then occurred, which prevented Astrobotic from achieving a stable sun-pointing orientation. The team is responding in real time as the situation unfolds and will be providing updates as more data is obtained and analyzed.”
Batteries are draining
Less than an hour after its initial statement on the anomaly, Astrobotic issued a second update that sounded fairly ominous.
“We continue to gather data and report our best assessment of what we see,” the company said. “The team believes that the likely cause of the unstable sun-pointing is a propulsion anomaly that, if proven true, threatens the ability of the spacecraft to soft land on the Moon.”
Peregrine will need its main engine to control the spacecraft’s descent down to the lunar surface. Based on additional information provided by the company, it appears that time is running out to fix the problem.
“As the team fights to troubleshoot the issue, the spacecraft battery is reaching operationally low levels,” Astrobotic said. “Just before entering a known period of communication outage, the team developed and executed an improvised maneuver to reorient the solar panels toward the Sun. Shortly after this maneuver, the spacecraft entered an expected period of communication loss.”
According to NASA’s Deep Space Network website, Peregrine reestablished communication with the controllers on Earth by around 11: 30 am ET. The communication then stopped again about 15 minutes later.
Taking shots on goal
If engineers can address the pointing problem and get Peregrine powered back up, there is time to work on the propulsion issue. Due to the spacecraft’s circuitous route to the Moon, Peregrine is not due to land there until February 23.
The spacecraft was privately built and largely funded by NASA through its Commercial Lunar Payload Services Program. The US space agency paid $108 million for the delivery of several science experiments to the Moon, including a radiation sensor, spectrometers, and a laser retroreflector array on board Peregrine. Astrobotic has also sold some payload space to private companies.
With this commercial program, NASA chose to procure a lunar delivery service rather than building a lander on its own. This cost the agency significantly less but entailed more risk. The agency also has funded a lander built by another company, Intuitive Machines, that could launch next month on a Falcon 9 rocket. About 10 more commercial lunar payload missions are in the pipeline.
The former leader of NASA’s scientific programs, Thomas Zurbuchen, has previously said this innovative lunar program was designed with speed in mind and that the agency would tolerate some failures as it takes “shots on goal” in attempting to land on the Moon. “We do not expect every launch and landing to be successful.”
This story has been updated to reflect the issuance of a second statement by Astrobotic.
Enlarge/ Lower Manhattan and One World Trade Center in New York City are reflected on a monument as the sun rises on December 22, 2023, as seen from Jersey City, New Jersey.
Unless you’re sinking into quicksand, you might assume that the land beneath your feet is solid and unmoving. In actual fact, your part of the world may well be undergoing “subsidence,” which is where the ground collapses as sediments settle or when people over-extract groundwater. New York City is sinking, too, due to the weight of all those buildings pushing on the ground. In extreme cases, like in California’s agriculturally intensive San Joaquin Valley, elevations have plummeted not by inches, but by dozens of feet.
Last year, scientists reported that the US Atlantic Coast is dropping by several millimeters annually, with some areas, like Delaware, notching figures several times that rate. So just as the seas are rising, the land along the eastern seaboard is sinking, greatly compounding the hazard for coastal communities.
In a follow-up study just published in the journal PNAS Nexus, the researchers tally up the mounting costs of subsidence—due to settling, groundwater extraction, and other factors—for those communities and their infrastructure. Using satellite measurements, they have found that up to 74,000 square kilometers (29,000 square miles) of the Atlantic Coast are exposed to subsidence of up to 2 millimeters (0.079 inches) a year, affecting up to 14 million people and 6 million properties. And over 3,700 square kilometers along the Atlantic Coast are sinking more than 5 millimeters annually. That’s an even faster change than sea-level rise, currently at 4 millimeters a year. (In the map below, warmer colors represent more subsidence, up to 6 millimeters.)
With each millimeter of subsidence, it gets easier for storm surges—essentially a wall of seawater, which hurricanes are particularly good at pushing onshore—to creep farther inland, destroying more and more infrastructure. “And it’s not just about sea levels,” says the study’s lead author, Leonard Ohenhen, an environmental security expert at Virginia Tech. “You also have potential to disrupt the topography of the land, for example, so you have areas that can get full of flooding when it rains.”
A few millimeters of annual subsidence may not sound like much, but these forces are relentless: Unless coastal areas stop extracting groundwater, the land will keep sinking deeper and deeper. The social forces are relentless, too, as more people around the world move to coastal cities, creating even more demand for groundwater. “There are processes that are sometimes even cyclic, for example in summers you pump a lot more water so land subsides rapidly in a short period of time,” says Manoochehr Shirzaei, an environmental security expert at Virginia Tech and coauthor of the paper. “That causes large areas to subside below a threshold that leads the water to flood a large area.” When it comes to flooding, falling elevation of land is a tipping element that has been largely ignored by research so far, Shirzaei says.
In Jakarta, Indonesia, for example, the land is sinking nearly a foot a year because of collapsing aquifers. Accordingly, within the next three decades, 95 percent of North Jakarta could be underwater. The city is planning a giant seawall to hold back the ocean, but it’ll be useless unless subsidence is stopped.
This new study warns that levees and other critical infrastructure along the Atlantic Coast are in similar danger. If the land were to sink uniformly, you might just need to keep raising the elevation of a levee to compensate. But the bigger problem is “differential subsidence,” in which different areas of land sink at different rates. “If you have a building or a runway or something that’s settling uniformly, it’s probably not that big a deal,” says Tom Parsons, a geophysicist with the United States Geological Survey who studies subsidence but wasn’t involved in the new paper. “But if you have one end that’s sinking faster than the other, then you start to distort things.”
Enlarge/ An example of a Littorina species, the common periwinkle.
The version of evolution proposed by Charles Darwin focused on slow, incremental changes that only gradually build into the sort of differences that separate species. But that doesn’t rule out the potential for sudden, dramatic changes. Indeed, some differences make it difficult to understand what a transitional state would look like, suggesting that a major leap might be needed.
A new study looks at one major transition: the shift from egg-laying to live births in a set of related snail species. By sequencing the genomes of multiple snails, the researchers identified the changes in DNA that are associated with egg-laying. It turns out that a large number of genes are associated with the change despite its dramatic nature.
Giving up eggs
The snails in question are in a genus called Littorina, which are largely distributed around the North Atlantic. Many of these species lay eggs, but a number of them have transitioned to live births. In these species, an organ that coats eggs with a protein-rich jelly in other species instead acts as an incubator, allowing eggs to develop until young snails can crawl out of their parent’s shells. This is thought to be an advantage for animals that would otherwise have to lay eggs in environments that aren’t favorable for their survival.
The egg laying species are so similar to their relatives that they were sometimes thought to just be a variant of an egg-laying species. All of which suggests that live birth has evolved relatively recently, giving us a good opportunity to understand the genetic changes that enabled it.
So, a large international team of researchers sequenced the genomes of over 100 individual snails, both egg-laying and live birth. The resulting data was used to analyze things like how closely related different species are, and what genetic changes are associated with live birth.
The results suggest that there are two separate clusters of species that reproduce through live births. Put differently, on an evolutionary tree of these snail species, there’s a branch full of egg-laying species separating two groups that give birth to live snails. Typically, this structure is viewed as an indication that live births evolved twice, once for each of the two clusters.
But that doesn’t seem to be the case here, for reasons that we’ll get into.
Lots of variations
Separately, the researchers looked for regions of the genome that are associated with giving live births. And they found lots of them—88 in total. These 88 regions were identified in both clusters of live-birth species, and the DNA sequences within them were very similar. This suggests that these regions had a single origin and were maintained in both these lineages.
One possibility to explain this is that a population of live-birth animals reverted to egg-laying at some point in their evolution. Alternatively, hybridization between egg-layers and live-birthers could have let these variations spread within an egg-laying population and ultimately re-enable live births when enough of them were present in individual animals, producing a separate live-birth lineage.
The 88 regions identified as underlying live births have very little genetic diversity, suggesting that a specific genetic variant in each region is so advantageous that it swept through the population, displacing all other versions of the stretch of DNA. They have, however, picked up some distinct variations that are rare outside the egg-laying populations—enough to allow the researchers to estimate the age when these pieces of DNA came under evolutionary selection.
The answer varies depending on which of the 88 segments you’re looking at, but it ranges from about 10,000 to 100,000 years ago. That range suggests that the genetic regions that enable live births were put together gradually over many years—exactly as the traditional view of evolution suggests.
The researchers acknowledge that at least some of these regions are likely to have evolved after live births were already the norm and simply improve the efficiency of the internal incubation. And there’s no way to know how many variants (or which) need to be present before live births are possible. However, the researchers now have an extensive list of genes to look into to understand things better.
Enlarge / This Scanning Electron Microscope image depicts several clusters of aerobic Gram-negative, non-motile Acinetobacter baumannii bacteria under a magnification of 24,730x.
A new experimental antibiotic can handily knock off one of the world’s most notoriously drug-resistant and deadly bacteria —in lab dishes and mice, at least. It does so with a never-before-seen method, cracking open an entirely new class of drugs that could yield more desperately needed new therapies for fighting drug-resistant infections.
The findings appeared this week in a pair of papers published in Nature, which lay out the extensive drug development work conducted by researchers at Harvard University and the Swiss-based pharmaceutical company Roche.
In an accompanying commentary, chemists Morgan Gugger and Paul Hergenrother of the University of Illinois at Urbana-Champaign discussed the findings with optimism, noting that it has been more than 50 years since the Food and Drug Administration has approved a new class of antibiotics against the category of bacteria the drug targets: Gram-negative bacteria. This category—which includes gut pathogens such as E. coli, Salmonella, Shigella, and the bacteria that cause chlamydia, the bubonic plague, gonorrhea, whooping cough, cholera, and typhoid, to name a few—is extraordinarily challenging to kill because it’s defined by having a complex membrane structure that blocks most drugs, and it’s good at accumulating other drug-resistance strategies
Weighty finding
In this case, the new drug—dubbed zosurabalpin—fights off the Gram-negative bacterium carbapenem-resistant Acinetobacter baumannii, aka CRAB. Though it may sound obscure, it’s an opportunistic, invasive bacteria that often strikes hospitalized and critically ill patients, causing deadly infections worldwide. It is extensively drug-resistant, with ongoing emergence of pan-resistant strains around the world—in other words, strains that are resistant to every current antibiotic available. Mortality rates of invasive CRAB infections range from 40 to 60 percent. In 2017, the World Health Organization listed it as a priority 1: critical pathogen, for which new antibiotics are needed most urgently.
Zosurabalpin may just end up being that urgently needed drug, as Gugger and Hergenrother write in their commentary: “Given that zosurabalpin is already being tested in clinical trials, the future looks promising, with the possibility of a new antibiotic class being finally on the horizon for invasive CRAB infections.”
An international team of researchers, led by Michael Lobritz and Kenneth Bradley at Roche, first identified a precursor of zosurabalpin through an unusual screen. Most new antibiotics are small molecules—those that have molecular weights of less than 600 daltons. But in this case, researchers searched through a collection of 45,000 bigger, heavier compounds, called tethered macrocyclic peptides (MCPs), which have weights around 800 daltons. The molecules were screened against a collection of Gram-negative strains, including an A. baumannii strain. A group of compounds knocked back the bacteria, and the researchers selected the top one—with the handy handle of RO7036668. The molecule was then optimized and fine-tuned, including charge balancing, to make it more effective, soluble, and safe. This resulted in zosurabalpin.
Deadly drug
In further experiments, zosurabalpin proved effective at killing a collection of 129 clinical CRAB isolates, many of which were difficult-to-treat isolates. The experimental drug was also effective at ridding mice of infections with a pan-resistant A. baumannii isolate, meaning however the drug worked, it could circumvent existing resistance mechanisms.
Next, the researchers worked to figure out how zosurabalpin was killing off these pan-resistant, deadly bacteria. They did this using a standard method of subjecting the bacteria to varying concentrations of the antibiotic to induce spontaneous mutations. For bacteria that developed tolerance to zosurabalpin, the researchers used whole genome sequencing to identify where the mutations were. They found 43 distinct mutations, and most were in genes encoding LPS transport and biosynthesis machinery.
Enlarge/ The Notre-Dame de Paris has been under restoration since a devastating fire destroyed the main spire and roof in April 2019.
There’s rarely time to write about every cool science-y story that comes our way. So this year, we’re once again running a special Twelve Days of Christmas series of posts, highlighting one science story that fell through the cracks in 2023, each day from December 25 through January 5. Today: The Notre Dame cathedral in Paris has been undergoing extensive renovation in the wake of a devastating 2019 fire. Previously hidden portions of its structure have revealed the use of iron reinforcements in the earliest phases of the cathedral’s construction, making it the earliest known building of its type to do so.
On April 15, 2019, the world watched in collective horror as the famed Notre Dame cathedral in Paris was engulfed in flames. The magnificent cathedral’s roof and its support structure of 800-year-old oak timbers were destroyed when the main spire—750 tons of oak lined with lead—collapsed in flames, landing on the wooden roof. French President Emmanuel Macron vowed to rebuild the cathedral, and that work has continued steadily in the ensuing years; the current planned re-opening will occur on December 8, 2024.
If there is a silver lining to the destruction, it’s that the damage has revealed parts of the cathedral’s structure that were previously inaccessible, telling archaeologists and conservationists more about the materials originally used to construct Notre Dame in the mid-12th century. According to a March 2023 paper published in the journal PLoS ONE, the original builders used iron reinforcements during the initial phases, making Notre Dame the earliest building of its type to do so.
“The fire has shed light on certain uses of iron, such as the staples on the top of the upper walls which were totally hidden by the framework,” co-author Maxime L’Héritier of Université Paris told Gizmodo. “We could not have seen them without the blaze or a huge restoration. We believed that [the] great building yards of the 13th century had invented these construction processes using iron armatures, but now it seems that it all occurred at Notre Dame.”
Although no original plans for Notre Dame Cathedral exist, a couple of centuries after Notre Dame’s construction, other building projects left behind documents called building accounts or fabric accounts, which include information like materials purchases and payments to masons. But in the late 12th century, written documents weren’t yet widely used. In the early 1800s, the cathedral was crumbling, and architects Eugène Viollet-le-Duc and Jean-Baptiste-Antoine Lassus received a royal contract to restore the medieval structure. Working with relatively simple tools, Viollet-le-Duc left behind detailed, accurate drawings of the original architecture and his own restoration work.
Two hundred years later, art historian Stephen Murray and the late architectural historian Andrew Tallon of Vassar College carried laser scanners through the entire cathedral, including the space above the vault and several out-of-the-way spiral staircases, passages, and other hidden spaces. As for the cathedral’s much-praised acoustics, a group of French acousticians made detailed measurements of Notre Dame’s “soundscape” a few years before the fire. All of that data has been instrumental in helping architects and conservationists reconstruct the cathedral.
Enlarge/ The 2019 fire exposed iron staples in the top walls, inside a column in the nave, and in the tribunes of the choir.
M. L’Heritier et al. 2023
Other medieval French cathedrals built after Notre Dame, such as in Chartres, Bourges, or Reims, all used iron armatures, tie-rods, and chains. But until now, it hasn’t been clear to what extent the original builders of Notre Dame used iron in its construction. Harnessing and scaffolding gave researchers access to the upper parts of the cathedral, although some parts remained inaccessible. Still, L’Héritier et al. found extensive use of iron staples at different levels, with the lowest being two rows of staples in the floors of the second-level tribunes above the arches, as well as in the nave and choir.
Per the authors, some iron reinforcements clearly dated back to reconstruction efforts during the 19th century, most notably iron chains and tie rods in the top walls of the choir and above its upper vaults. The real question was just how old the other iron staples might be. The team mapped and measured all those that were accessible, totaling roughly 170 staples for the upper walls and 100 for the tribunes. They also took samples for the metallographic analysis from iron staples that were already broken or damaged by the fire. The team used a new method for characterizing metal, combined with radiocarbon dating, to determine the age and possible provenance of those samples.
L’Héritier et al. concluded that the iron staples in the floor of the tribunes dated back to the early 1160s, i.e., the earliest phases of construction. “So far, these series of staples are the earliest known example of iron armatures used in the initial design of a Gothic monument,” they wrote, a good 40 years before the iron reinforcements used to build the Chartres or Bourges cathedrals. The staples found at the top of the great lateral walls date to the early 13th century, indicating that the architects of that period also relied on iron reinforcements.
As for the iron itself, the metal analysis showed that the iron alloys used to make the staples were common to the Middle Ages and of similar quality to those found at Chartres, Troyes, and similar cathedrals. What makes the Notre Dame staples unusual is the presence of welding lines, indicating that several pieces of iron of different provenances were welded together to form each staple. Tracking those supply sources could shed light on the iron trade, circulation, and forging in 12th and 13th century Paris.
“Compared to other cathedrals, such as Reims, the structure of Notre Dame in Paris is light and elegant,” Jennifer Feltman of the University of Alabama, who was not involved in the research, told New Scientist. “This study confirms that use of iron made this lighter structure at Paris possible and thus the use of this material was crucial to the design of the first Gothic architect of Notre Dame.”
Enlarge/ United Launch Alliance hoists the Certification-1 payloads atop the Vulcan rocket in the Vertical Integration Facility adjacent to Space Launch Complex-41 at Cape Canaveral Space Force Station.
United Launch Alliance
It’s nearly time. After years of delays, billions of dollars in federal funding, and a spectacular second-stage explosion, the large and impressive Vulcan rocket is finally ready to take flight.
United Launch Alliance’s heavy lift vehicle underwent its final review on Thursday, and the company cleared the rocket for its debut flight. With weather looking favorable, the Vulcan rocket is on track to lift off at 2: 18 am ET (7: 18 UTC) on Monday from Cape Canaveral Space Force Station in Florida. The mission’s primary payload is a lunar lander built by Astrobotic, and the launch will be streamed live here.
This marks an absolutely pivotal moment for the 20-year-old launch company, which has gone from the titan of the US launch industry to playing a distant second fiddle to its one-time upstart competitor SpaceX. Last year, SpaceX launched 98 rockets. United Launch Alliance, or ULA, tallied just three. The owners of ULA, Lockheed Martin and Boeing, are also on the cusp of selling the launch company if they can find a buyer willing to pay the right price. And critically, for the first time, ULA will be flying a new vehicle it designed and developed on its own—a rocket with some but not a majority of its heritage from the legacy Atlas and Delta rockets that have flown since the Cold War.
So yeah, it’s a moment.
A little history
A quarter of a century ago, two of America’s largest aerospace contractors, Lockheed and Boeing, were the national leaders in providing launch services for the US military and many of NASA’s science missions. But they struggled to capture commercial satellite launches in an emerging market. Lockheed, with its Atlas rockets, and Boeing, with its Deltas, could not compete with Europe-based Arianespace and Russia on price. So the two US contractors doubled down on their competition for US government launch contracts.
The competition grew ugly, with allegations that Boeing stole rocket designs from Lockheed. The US Department of Justice began investigating how Boeing acquired tens of thousands of pages of trade secrets belonging to Lockheed Martin. There were lawsuits, and then questions about whether Boeing’s rocket business was viable. Military officials began to worry that if Boeing stopped flying the Delta, their only pathway into space would be through a Russian engine—the RD-180 that powered Lockheed’s Atlas V.
To ensure it had redundant access to space on two different rocket families, the military stepped in and arranged a shotgun marriage. The Department of Defense brokered a deal in which Lockheed and Boeing would merge their rocket-building ventures into one company, United Launch Alliance, in 2005. The parents retained a 50 percent ownership stake, and to sweeten the pot, the military agreed to pay a subsidy of about $1 billion a year.
Everything seemed to be working out well until SpaceX started launching rockets.
A little rivalry
ULA had tried to kill the baby. When SpaceX sought a launch site for its Falcon 9 rocket at Cape Canaveral in 2007, the parents lobbied the Air Force brass hard to stop the lease of Space Launch Complex-40 to Elon Musk and his rocket company. But the commander of the 45th Space Wing with oversight of Cape Canaveral, Gen. Susan Helms, approved the lease anyway.
Since then, ULA and SpaceX have been uneasy bedfellows in Florida, working side by side at nearby launch pads. Some of the rivalry was good-natured. Every week, for a while, engineers from SpaceX and ULA would meet up at Hogan’s Irish Bar in Cape Canaveral for trivia night. They would vie for nerd supremacy, drinking Guinness and blowing off steam.
But there have been more difficult confrontations. Musk kept pointing out the $1 billion subsidy at Congressional hearings—ULA officials bristled at the characterization of this ELC payment as a subsidy, but in effect, that’s what it was—and arguing that SpaceX’s Falcon 9 rocket could fly many of the military’s missions for much-reduced prices.
The issue came to a head in 2014, when the Air Force and ULA announced a new agreement for 36 national security launches to be flown during the remainder of the decade. ULA’s chief executive at the time, Mike Gass, hailed this “block buy” agreement because it would save the government $4.4 billion. Musk seethed. By then, his Falcon 9 rocket had launched eight times, all successfully. He sued the US government to stop the block buy and open up competition for the Falcon 9.
Several months into the lawsuit, SpaceX and the Air Force entered mediation. As part of the settlement, the military agreed to accelerate the certification of the Falcon 9 rocket and open up a number of the block buy launches to competition. SpaceX launched its first national security payload in 2017. SpaceX has not really looked back since.
Enlarge/ Jeff Bezos (right), the founder of Blue Origin and Amazon.com, and Tory Bruno, CEO of United Launch Alliance, display a small-scale version of the BE-4 rocket engine during a press conference in 2014.
Welcome to the Daily Telescope. There is a little too much darkness in this world and not enough light, a little too much pseudoscience and not enough science. We’ll let other publications offer you a daily horoscope. At Ars Technica, we’re going to take a different route, finding inspiration from very real images of a universe that is filled with stars and wonder.
Good morning. It’s January 5, and today’s photo reveals the Crab Nebula in all of its glory.
This object, known more formally as Messier 1 or M1, earned its colloquial name when Anglo-Irish astronomer William Parsons observed and drew this object in the early 1840s. It looked something like a crab with arms, and the appellation stuck. The nebula had been discovered about a century earlier by English astronomer John Bevis.
The nebula is actually a supernova remnant from a star that was observed popping in 1054 and recorded by Chinese astronomers. That must have been quite a sight, because the supernova occurred only about 2,000 light-years from Earth, which is relatively close as these things go. It likely was as bright as Venus and visible during daylight hours for a few weeks.
This image was captured by amateur astronomer Paul Macklin in Indiana. And it’s quite spectacular.
Enlarge/ Firefly Aerospace’s fourth Alpha rocket lifted off December 22 from Vandenberg Space Force Base, California.
Welcome to Edition 6.25 of the Rocket Report! We hope all our readers had a peaceful holiday break. While many of us were enjoying time off work, launch companies like SpaceX kept up the pace until the final days of 2023. Last year saw a record level of global launch activity, with 223 orbital launch attempts and 212 rockets successfully reaching orbit. Nearly half of these missions were by SpaceX.
As always, we welcome reader submissions, and if you don’t want to miss an issue, please subscribe using the box below (the form will not appear on AMP-enabled versions of the site). Each report will include information on small-, medium-, and heavy-lift rockets, as well as a quick look ahead at the next three launches on the calendar.
Firefly’s fourth launch puts payload in wrong orbit. The fourth flight of Firefly Aerospace’s Alpha rocket on December 22 placed a small Lockheed Martin technology demonstration satellite into a lower-than-planned orbit after lifting off from Vandenberg Space Force Base, California. US military tracking data indicated the Alpha rocket released its payload into an elliptical orbit ranging between 215 and 523 kilometers in altitude, not the mission’s intended circular target orbit. Firefly later confirmed the Alpha rocket’s second stage, which was supposed to reignite about 50 minutes after liftoff, did not deliver Lockheed Martin’s satellite into the proper orbit. This satellite, nicknamed Tantrum, was designed to test Lockheed Martin’s new wideband Electronically Steerable Antenna technology to demonstrate faster on-orbit sensor calibration to deliver rapid capabilities to US military forces.
Throwing a tantrum? … This was the third time in four flights that Firefly’s commercial Alpha rocket, designed to loft payloads up to a metric ton in mass, has not reached its orbital target. The first test flight in 2021 suffered an engine failure on the first stage before losing control shortly after liftoff. The second Alpha launch in 2022 deployed its satellites into a lower-than-planned orbit, leaving them unable to complete their missions. In September, Firefly launched a small US military satellite on a responsive launch demonstration. Firefly and the US Space Force declared that mission fully successful. Atmospheric drag will likely pull Lockheed Martin’s payload back into Earth’s atmosphere for a destructive reentry in a matter of weeks. The good news is ground teams are in contact with the satellite, so there could be a chance to complete at least some of the mission’s objectives. (submitted by Ken the Bin)
Australian startup nears first launch. The first locally made rocket to be launched into space from Australian soil is scheduled for liftoff from a commercial facility in Queensland early next year, the Australian Broadcasting Corporation reports. A company named Gilmour Space says it hopes to launch its first orbital-class Eris rocket in March, pending final approval from Australian regulatory authorities. This would be the first Australian-built orbital rocket, although a US-made rocket launched Australia’s first satellite from a military base in South Australia in 1967. The UK’s Black Arrow rocket also launched a satellite from the same remote Australian military base in 1971.
Getting to know Eris … The three-stage Eris rocket stands 25 meters (82 feet) tall with the ability to deliver up to 300 kilograms (660 pounds) of payload into low-Earth orbit, according to Gilmour Space. The company says the Eris rocket will be powered by Gilmour’s “new and proprietary hybrid rocket engine.” These kinds of propulsion systems use a solid fuel and a liquid oxidizer. We’ll be watching to see if Gilmour shares more tangible news about the progress toward the first Eris launch in March. In late 2022, the company targeted April 2023 for the first Eris flight, so this program has a history of delays. (submitted by Marzipan and Onychomys)
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A commander’s lament on the loss of a historic SpaceX booster. The Falcon 9 rocket that launched NASA astronauts Doug Hurley and Bob Behnken on SpaceX’s first crew mission in 2020 launched and landed for the 19th and final time just before Christmas, then tipped over on its recovery ship during the trip back to Cape Canaveral, Florida, Ars reports. This particular booster, known by the tail number B1058, was special among SpaceX’s fleet of reusable rockets. It was the fleet leader, having tallied 19 missions over the course of more than three-and-a-half years. More importantly, it was the rocket that thundered into space on May 30, 2020, on a flight that made history.
A museum piece? … The lower third of the booster was still on the deck of SpaceX’s recovery ship as it sailed into Port Canaveral on December 26. This portion of the rocket contains the nine Merlin engines and landing legs, some of which appeared mangled after the booster tipped over in high winds and waves. Hurley, who commanded SpaceX’s Crew Dragon spacecraft on the booster’s historic first flight in 2020, said he hopes to see the remaining parts of the rocket in a museum. “Hopefully they can do something because this is a little bit of an inauspicious way to end its flying career, with half of it down at the bottom of the Atlantic Ocean,” said Hurley.
SpaceX opens 2024 campaign with a new kind of Starlink satellite. SpaceX has launched the first six Starlink satellites that will provide cellular transmissions for customers of T-Mobile and other carriers, Ars reports. A Falcon 9 rocket launched from California on January 2 carried 21 Starlink satellites overall, including the first six Starlinks with Direct to Cell capabilities. SpaceX says these satellites, and thousands of others to follow, will “enable mobile network operators around the world to provide seamless global access to texting, calling, and browsing wherever you may be on land, lakes, or coastal waters without changing hardware or firmware.” T-Mobile said that field testing of Starlink satellites with the T-Mobile network will begin soon. “The enhanced Starlink satellites have an advanced modem that acts as a cellphone tower in space, eliminating dead zones with network integration similar to a standard roaming partner,” SpaceX said.
Two of 144 … SpaceX followed this launch with another Falcon 9 flight from Florida on January 3 carrying a Swedish telecommunications satellite. These were the company’s first two missions of 2024, a year when SpaceX officials aim to launch up to 144 rockets, an average of 12 per month, exceeding the 98 rockets it launched in 2023. A big focus of SpaceX’s 2024 launch manifest will be delivering these Starlink Direct to Cell satellites into orbit. (submitted by Ken the Bin)
Chinese booster lands near homes. China added a new pair of satellites to its Beidou positioning and navigation system on December 25, but spent stages from the launch landed within inhabited areas, Space News reports. Meanwhile, a pair of the side boosters from the Long March 3B rocket used for the launch appeared to fall to the ground near inhabited areas in Guangxi region, downrange of the Xichang spaceport in Sichuan province, according to apparent bystander footage on Chinese social media. One video shows a booster falling within a forested area and exploding, while another shows a falling booster and later, wreckage next to a home.
Life downrange … Chinese government authorities reportedly issue warnings and evacuation notices for citizens living in regions where spent rocket boosters are likely to fall after launch, but these videos clearly show people are still close by as the rockets fall from the sky. We’ve seen this kind of imagery before, including views of a rocket that crashed into a rural building in 2019. What’s more, the rockets return to Earth with leftover toxic propellants—hydrazine and nitrogen tetroxide—that could be deadly to breathe or touch. Clouds of brownish-orange gas are visible around the rocket wreckage, an indication of the presence of nitrogen tetroxide. China built its three Cold War-era spaceports in interior regions to protect them from possible military attacks, while its newest launch site is at a coastal location on Hainan Island, allowing rockets launched there to drop boosters into the sea. (submitted by Ken the Bin and EllPeaTea)
Launch date set for next H3 test flight. The second flight of Japan’s new flagship H3 rocket is scheduled for February 14 (US time; February 15 in Japan), the Japan Aerospace Exploration Agency announced on December 28. This will come nearly one year after the first H3 test flight failed to reach orbit last March when the rocket’s second stage failed to ignite a few minutes after liftoff. This failure destroyed a pricey Japanese Earth observation satellite and dealt a setback to Japan’s rocket program. The H3 is designed to be cheaper and more capable than the H-IIA and H-IIB rockets it will replace. Eventually, the H3 will launch Japan’s scientific research probes, spy satellites, and commercial payloads.
Fixes since the first flight … Engineers narrowed the likely cause for the first H3 launch failure to an electrical issue, although Japanese officials have not provided an update on the investigation for several months. In August, Japan’s space agency said investigators had narrowed the cause of the H3’s second-stage malfunction to three possible failure scenarios. Nevertheless, officials are apparently satisfied the H3 is ready to fly again. But this time, there won’t be an expensive satellite aboard. A dummy payload will fly inside the H3 rocket’s nose cone, along with two relatively low-cost small satellites hitching a piggyback ride to orbit. (submitted by Ken the Bin and EllPeaTea)
India’s PSLV launches first space mission of 2024. The first orbital launch of the new year, as measured in the globally recognized Coordinated Universal Time, or UTC, was the flight of an Indian Polar Satellite Launch Vehicle (PSLV) on January 1 (December 31 in the United States). This launch deployed an X-ray astronomy satellite named XPoSat, which will measure X-ray emissions from black holes, neutron stars, active galactic nuclei, and pulsars. This is India’s first X-ray astronomy satellite, and its launch is another sign of India’s ascendence among the world’s space powers. India has some of the world’s most reliable launch vehicles, is developing a human-rated capsule to carry astronauts into orbit, and landed its first robotic mission on the Moon last year.
Going lower … After releasing the XPoSat payload, the PSLV’s fourth stage lowered its orbit to begin an extended mission hosting 10 scientific and technology demonstration experiments. These payloads will test new radiation shielding technologies, green propulsion, and fuel cells in orbit, according to the Indian Space Research Organization. On missions with excess payload capacity, India has started offering researchers and commercial companies the opportunity to fly experiments on the PSLV fourth stage, which has its own solar power source to essentially turn itself from a rocket into a satellite platform. (submitted by EllPeaTea and Ken the Bin)
Mixed crews will continue flying to the International Space Station. NASA and the Russian space agency, Roscosmos, will extend an agreement on flying each other’s crew members to the International Space Station through 2025, Interfax reports. This means SpaceX’s Crew Dragon spacecraft and Boeing’s Starliner capsule, once operational, will continue transporting Russian cosmonauts to and from the space station, as several recent SpaceX crew missions have done. In exchange, Russia will continue flying US astronauts on Soyuz missions.
There’s a good reason for this… Despite poor relations on Earth, the US and Russian governments continue to be partners on the ISS. While NASA no longer has to pay for seats on Soyuz spacecraft, the US space agency still wants to fly its astronauts on Soyuz to protect against the potential for a failure or lengthy delay with a SpaceX or Boeing crew mission. Such an event could lead to a situation where the space station has no US astronauts aboard. Likewise, Roscosmos benefits from this arrangement to ensure there’s always a Russian on the space station, even in the event of a problem with Soyuz. (submitted by Ken the Bin)
SpaceX sets new records to close out 2023. SpaceX launched two rockets, three hours apart, to wrap up a record-setting 2023 launch campaign, Ars reports. On December 28, SpaceX launched a Falcon Heavy rocket from NASA’s Kennedy Space Center in Florida with the US military’s super-secret X-37B spaceplane. Less than three hours later, a Falcon 9 rocket took off a few miles to the south with another batch of Starlink Internet satellites. These were SpaceX’s final launches of 2023. SpaceX ended the year with 98 flights, including 91 Falcon 9s, five Falcon Heavy rockets, and two test launches of the giant new Super Heavy-Starship rocket. These flights were spread across four launch pads in Florida, California, and Texas. It was also the shortest turnaround between two SpaceX flights in the company’s history, and set a modern-era record at Cape Canaveral, Florida, with the shortest span between two orbital-class launches there since 1966.
Where’s the X-37B?… The military’s reusable X-37B spaceplane that launched on the Falcon Heavy rocket apparently headed into an unusually high orbit, much higher than the spaceplane program’s previous six flights. But the military kept the exact orbit a secret, and amateur skywatchers will be closely watching for signs of the spaceplane passing overhead in hopes of estimating its apogee, perigee, and inclination. What the spaceplane is doing is also largely a mystery. The X-37B resembles a miniature version of NASA’s retired space shuttle orbiter, with wings, deployable landing gear, and black thermal protection tiles to shield its belly from the scorching heat of reentry.
Elon Musk says SpaceX needs to built a lot of Starships. Even with reusability, SpaceX will need to build Starships as often as Boeing builds 737 jetliners in order to realize Elon Musk’s ambition for a Mars settlement, Ars reports. “To achieve Mars colonization in roughly three decades, we need ship production to be 100/year, but ideally rising to 300/year,” Musk wrote on his social media platform X. SpaceX still aims to make the Starship and its Super Heavy booster rapidly reusable. The crux is that the ship, the part that would travel into orbit, and eventually to the Moon or Mars, won’t be reused as often as the booster. These ships will come in a number of different configurations, including crew and cargo transports, refueling ships, fuel depots, and satellite deployers.
Laws of physics… The first stage of the giant launch vehicle, named Super Heavy, is designed to return to SpaceX’s launch sites about six minutes after liftoff, similar to the way SpaceX recovers its Falcon boosters today. Theoretically, Musk wrote, the booster could be ready for another flight in an hour. With the Starship itself, the laws of physics and the realities of geography come into play. As an object flies in low-Earth orbit, the Earth rotates underneath it. This means that a satellite, or Starship, will find itself offset some 22.5 degrees in longitude from its launch site after a single 90-minute orbit around the planet. It could take several hours, or up to a day, for a Starship in low-Earth orbit to line up with one of the recovery sites. “The ship needs to complete at least one orbit, but often several to have the ground track line back up with the launch site, so reuse may only be daily,” Musk wrote. “This means that ship production needs to be roughly an order of magnitude higher than booster production.”
Next three launches
January 5: Kuaizhou 1A | Unknown Payload | Jiuquan Satellite Launch Center, China | 11: 20 UTC
January 7: Falcon 9 | Starlink 6-35 | Cape Canaveral Space Force Station, Florida | 21: 00 UTC
January 8: Falcon 9 | Starlink 7-10 | Vandenberg Space Force Base, California | 05: 00 UTC
Enlarge / Daniel Simons and Christopher Chabris are the authors of Nobody’s Fool: Why We Get Taken In and What We Can Do About It.
Basic Books
There’s rarely time to write about every cool science-y story that comes our way. So this year, we’re once again running a special Twelve Days of Christmas series of posts, highlighting one science story that fell through the cracks in 2023, each day from December 25 through January 5. Today: A conversation with psychologists Daniel Simons and Christopher Chabris on the key habits of thinking and reasoning that may serve us well most of the time, but can make us vulnerable to being fooled.
It’s one of the most famous experiments in psychology. Back in 1999, Daniel Simons and Christopher Chabris conducted an experiment on inattentional blindness. They asked test subjects to watch a short video in which six people—half in white T-shirts, half in black ones—passed basketballs around. The subjects were asked to count the number of passes made by the people in white shirts. Halfway through the video, a person in a gorilla suit walked into the midst of the players and thumped their chest at the camera before strolling off-screen. What surprised the researchers was that fully half the test subjects were so busy counting the number of basketball passes that they never saw the gorilla.
The experiment became a viral sensation—helped by the amusing paper title, “Gorillas in Our Midst“—and snagged Simons and Chabris the 2004 Ig Nobel Psychology Prize. It also became the basis of their bestselling 2010 book, The Invisible Gorilla: How Our Intuitions Deceive Us. Thirteen years later, the two psychologists are back with their latest book, published last July, called Nobody’s Fool: Why We Get Taken In and What We Can Do About It. Simons and Chabris have penned an entertaining examination of key habits of thinking that usually serve us well but also make us vulnerable to cons and scams. They also offer some practical tools based on cognitive science to help us spot deceptions before being taken in.
“People love reading about cons, yet they keep happening,” Simons told Ars. “Why do they keep happening? What is it those cons are tapping into? Why do we not learn from reading about Theranos? We realized there was a set of cognitive principles that seemed to apply across all of the domains, from cheating in sports and chess to cheating in finance and biotech. That became our organizing theme.”
Ars spoke with Simons and Chabris to learn more.
Ars Technica: I was surprised to learn that people still fall for basic scams like the Nigerian Prince scam. It reminds me of Fox Mulder’s poster on The X-Files: “I want to believe.“
Daniel Simons: The Nigerian Prince scam is an interesting one because it’s been around forever. Its original form was in letters. Most people don’t get fooled by that one. The vast majority of people look at it and say, this thing is written in terrible grammar. It’s a mess. And why would anybody believe that they’re the one to recover this vast fortune? So there are some people who fall for it, but it’s a tiny percentage of people. I think it’s still illustrative because that one is obviously too good to be true for most people, but there’s some small subset of people for whom it’s just good enough. It’s just appealing enough to say, “Oh yeah, maybe I could become rich.”
There was a profile in the New Yorker of a clinical psychologist who fell for it. There are people who, for whatever reason, are either desperate or have the idea that they deserve to inherit a lot of money. But there are a lot of scams that are much less obvious than that one, selecting for the people who are most naive about it. I think the key insight there is that we tend to assume that only gullible people fall for this stuff. That is fundamentally wrong. We all fall for this stuff if it’s framed in the right way.
Christopher Chabris: I don’t think they’re necessarily people who always want to believe. I think it really depends on the situation. Some people might want to believe that they can strike it rich in crypto, but they would never fall for a Nigerian email or, for that matter, they might not fall for a traditional Ponzi scheme because they don’t believe in fiat money or the stock market. Going back to the Invisible Gorilla, one thing we noticed was a lot of people would ask us, “What’s the difference between the people who noticed the gorilla and the people who didn’t notice the gorilla?” The answer is, well, some of them happened to notice it and some of them didn’t. It’s not an IQ or personality test. So in the case of the Nigerian email, there might’ve been something going on in that guy’s life at that moment when he got that email that maybe led him to initially accept the premise as true, even though he knew it seemed kind of weird. Then, he got committed to the idea once he started interacting with these people.
Christopher Chabris
So one of our principles is commitment: the idea that if you accept something as true and you don’t question it anymore, then all kinds of bad decisions and bad outcomes can flow from that. So, if you somehow actually get convinced that these guys in Nigeria are real, that can explain the bad decisions you make after that. I think there’s a lot of unpredictableness about it. We all need to understand how these things work. We might think it sounds crazy and we would never fall for it, but we might if it was a different scam at a different time.
Enlarge/ Sol, imaged by NASA’s Solar Dynamics Observatory.
NASA
Welcome to the Daily Telescope. There is a little too much darkness in this world and not enough light, a little too much pseudoscience and not enough science. We’ll let other publications offer you a daily horoscope. At Ars Technica, we’re going to take a different route, finding inspiration from very real images of a universe that is filled with stars and wonder.
Good morning. It’s January 4, and today’s image is a photo of our star, Sol. The image was captured by NASA’s Solar Dynamics Observatory, a spacecraft in geosynchronous orbit, on Wednesday.
So why a picture of the Sun? Because we’ve just passed perihelion, the point at which planet Earth reaches its closest point to the Sun. This year perihelion came at 00: 38 UTC on Wednesday, January 3. We got to within about 91.4 million miles (147 million km) of the star. Due to its slightly elliptical orbit around the Sun, Earth will reach aphelion this year on July 5, at a distance of 94.5 million miles (152 million km).
There is a bit of irony for those of us who live in the Northern Hemisphere, of course. We approach nearest to the Sun at almost the coldest time of year, just a couple of weeks after the winter solstice. Our planet’s seasons are determined by Earth’s axial tilt, however, not its proximity to the Sun.
In any case, happy new year, a time when the world can seem full of possibility—shiny and bright like a star.
What draws us to choose romantic partners? A sweeping new meta-analysis suggests we gravitate toward certain shared traits.
There’s rarely time to write about every cool science-y story that comes our way. So this year, we’re once again running a special Twelve Days of Christmas series of posts, highlighting one science story that fell through the cracks in 2023, each day from December 25 through January 5. Today: a broad meta-analysis spanning over a century of studies finds that opposites don’t really attract when it comes to choosing a mate.
We’ve all heard the common folk wisdom that when it comes to forming romantic partnerships, opposites attract. Researchers at the University of Colorado, Boulder, contend that this proverbial wisdom is largely false, based on the findings of their sweeping September study, published in the journal Nature Human Behavior. The saying, “birds of a feather flock together,” is a more apt summation of how we choose our partners.
“These findings suggest that even in situations where we feel like we have a choice about our relationships, there may be mechanisms happening behind the scenes of which we aren’t fully aware,” said co-author Tanya Horwitz, a psychology and neuroscience graduate student at UCB. “We’re hoping people can use this data to do their own analyses and learn more about how and why people end up in the relationships they do.”
Horwitz et al. conducted a systematic review of peer-reviewed studies in the English language involving comparisons of the same or similar complex traits in partners, all published before August 17, 2022, with the oldest dated 1903. They excluded same-sex/gender partners, maintaining that these partnerships warranted a separate analysis since the patterns could differ significantly. The meta-analysis focused on 22 distinct traits. The team also conducted a raw data analysis of an additional 133 traits, drawing from the UK’s Biobank dataset, one of the largest and most detailed in the world for health-related information on more than 500,000 people. All told, the study encompassed millions of couples spanning over a century: co-parents, engaged pairs, married pairs, and cohabitating pairs.
The personality traits included were based on the so-called Big Five basic personality traits: neuroticism, extraversion, openness, agreeableness, and conscientiousness. (The Big Five is currently the professional standard for social psychologists who study personality. Here’s a good summary of what those traits mean to psychologists.) The other traits studied included such things as educational attainment, IQ score, political values, religiosity, problematic alcohol use, drinking, quitting smoking, starting smoking, quantity of smoking, smoker status, substance use disorder, BMI, height, waist-to-hip ratio, depression, diabetes, generalized anxiety, whether they were breastfed as a child, and age of first intercourse, among others.
The meta-analysis and Biobank analysis revealed that the strongest correlations for couples were for birth year and traits like political and religious attitudes, educational attainment, and certain IQ measures. Couples tend to be similar when it comes to their substance use, too: heavy drinkers tend to be with other heavy drinkers, and teetotalers tend to pair with fellow teetotalers. There were a handful of traits among the Biobank couples where opposites did seem to attract, most notably whether one is a morning person or a night owl, tendency to worry, and hearing difficulty.
The weakest correlations were for traits like height, weight, medical conditions, and personality traits, although these were still mostly positive, apart from extroversion, which somewhat surprisingly showed almost no correlation. “People have all these theories that extroverts like introverts or extroverts like other extroverts, but the fact of the matter is that it’s about like flipping a coin,” said Horwitz. “Extroverts are similarly likely to end up with extroverts as with introverts.”
Horwitz et al. cautioned that even the strongest correlations they found were still fairly modest. As for why couples show such striking similarities, the authors write that there could be many reasons. Some people might just be attracted to similar sorts, or couples might become more similar over time. (The study also found that the strength of the correlations changed over time.) Perhaps two people who grow up in the same geographical area or a similar home environment might naturally find themselves drawn to each other.
The authors were careful to note several limitations to their meta-analysis. Most notably, most of those partners sampled came from Europe and the United States, with only a handful coming from East and South Asia, Africa, Latin America, and the Caribbean. Furthermore, all participants in the UK Biobank dataset were between the ages of 40 and 69 when they were originally recruited, all of whom were less likely to smoke, be socioeconomically deprived, or drink daily. The studies included in the meta-analysis also varied widely regarding sample sizes used to draw correlations across traits. For these reasons, the authors caution that their findings “are unlikely to be generalizable to all human populations and time periods.”
