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Details pour in from New Horizons’ visit to a Kuiper Belt Object

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NASA/JHU APL/SWRI/Roman Tkachenko

Following its successful rendezvous with Pluto, the New Horizons spacecraft was sent on towards a smaller object out in the Kuiper Belt. As it shot past, the spacecraft captured images of a small world consisting of two very distinct lobes, with properties that scientists found a bit confusing. But details would have to wait, as the combination of distance and power budget meant that transmitting much of New Horizons’ data back to Earth was a slow process.

The wait for that data is now over, as the high-resolution imagery is now available, and scientists have used it to try to better understand the formation and structure of what is now known as Arrokoth (named for the Powhatan word for “sky”). While the data doesn’t answer every question we might have about Arrokoth, it does give us some very good ideas about how such a strange structure could have formed.

Can’t stay long

New Horizons was the fastest probe as launched from Earth (others have since picked up more speed thanks to gravity assists), and Arrokoth is very small, meaning the probe had to get rather close before it could be imaged in any detail. That left a narrow window for gathering data during the flyby, but the papers released today details just how narrow it was. As little as two days before the closest pass, Arrokoth was still showing up as a single pixel in New Horizons’ cameras. It didn’t grow larger than 10 pixels until about a half day before. So the vast majority of the data comes from a window that’s just 12 hours wide.

Still, during that time, the cameras on board New Horizons captured images that probed the composition of Arrokoth, and they were able to resolve features as small as 33 meters across on its surface. The papers that ensued describe the body’s structure, model its history, and take some guesses at its chemistry.

Arrokoth comes from a region of the Solar System called the Kuiper Belt, specifically from an area that’s outside the gravitational influence of Neptune, the outermost large planet. In this region, there was enough material to form icy bodies, but it was spread so thinly that the bodies seem to have remained small, without interacting frequently enough to form larger planets. Neptune’s influence scattered some of the Kuiper Belt objects further inward, where collisions with other bodies were more likely and the influence of the Sun was stronger. But Arrokoth currently orbits beyond the point where that was likely to happen.

If true, that means the object is likely to be comprised of material that is largely unchanged since the formation of the Solar System. And, by all indications, it is true. Evaluations of the crater density on the surface of Arrokoth is consistent with an age of four billion years, that of the Solar System itself. And the surface has the red color typical of other objects from this region of the Kuiper belt, suggesting that its surface hasn’t seen significant chemical modification.

The red color seems to come from a complicated mix of longer-chain hydrocarbons collectively called tholins. These are built by chemical reactions among shorter molecules driven by radiation exposure. In Arrokoth’s case, those shorter molecules appear to include methanol, a single-carbon alcohol, and the only individual chemical clearly identified in the New Horizons data. Methanol could have formed by chemical reactions between methane and water, but there’s only weak indications of the presence of water on Arrokoth, and no clear signature of methane. It’s possible—even likely, given what we know about the Kuiper Belt and other objects from it&mdahs;that they’re present below the surface, but that hasn’t been confirmed by this flyby.

Whatever it’s made of, Arrokoth isn’t very dense, and is likely similar to those of comets. If it’s less than half as dense as a typical comet, it’s spinning fast enough that it would come apart. Too much more dense, and the two lobes would have crushed each other more when they came together.

How two became one

One of the things that demands an explanation is Arrokoth’s unusual shape. It appears to be what’s called a “contact binary,” meaning it formed by two objects gently being smushed against each other. But in this case, the objects themselves had appeared to be a bit smushed, requiring their flattened, elongated shape to also be explained.

One of the key results of the flyby was the generation of two successive images from slightly different perspectives, allowing a stereoscopic view of Arrokoth. The 3D reconstruction built form that view indicates that the two lobes aren’t as flattened as they had originally appeared. This level of flattening could be explained by the spin of each object, and the more rounded shape means that the spin of each part would only have to be slightly higher than the current spin of Arrokoth in order to create the appropriate degree of flatness.

Modeling of the sorts of collisions that might bring two separate bodies together indicated that any approach speed over about five meters a second would lead to some fracturing of the two bodies, rather than the neat two-lobed structure we see. This suggests the two bodies must have formed in proximity to each other, from the same collapsing cloud of material. Anything other than that is unlikely to provide this sort of gradual approach speed.

But even a slow approach like the two objects experienced would have required something to bleed away their original momentum. So, the researchers considered a variety of items that could have done so. But a lot of the easy options just won’t work. Arrokoth is simply too far from the Sun—over 40 times the Earth’s distance from the Sun—for light to have had a significant affect on the bodies’ motion. Collisions haven’t been frequent enough to bleed off enough of the momentum.

What they researchers were left with is the gas that originally orbited the Sun early in the Solar System’s history. While the Sun’s energy drove off most of this gas, it would have been present at the time the two bodies originally formed and, more critically, would have orbited the Sun more slowly. This would have provided a friction to the two bodies that formed Arrokoth, allowing them to approach slowly enough to fuse without shattering either of them at the point where they first contacted.

No rings, big crater

The single largest feature on Arrokoth is a crater that’s picked up the nickname “Maryland,” after the site of the New Horizons control center. Maryland is on the smaller of the two lobes and is about six kilometers across and at least a half-kilometer deep. Its otherwise round outline is interrupted by an outcrop that extends into the crater; how it formed is not clear. There are plenty of smaller depressions that appear to be craters, but none of them are more than a kilometer across.

Craters typically mean that material was blasted off the surface of a small body like Arrokoth, so the researchers scanned for their remains: small moons or rings, which have been found on other minor Solar System objects. But there were no signs of any moons, and if a ring is present, it’s incredibly sparse.

There are lots of further details that have already been explored—three papers mean a lot of text and supplemental data. But the publication of the data also means that people who study other Solar System processes and Kuiper belt objects will start rethinking their objects of interest in light of what we now know about Arrokoth. And the publications on those will probably keep coming for a decade or more.

Science, 2020. DOI: 10.1126/science.aay3705, 10.1126/science.aay6620, 10.1126/science.aay3999  (About DOIs).

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As Florida punishes schools, study finds masks cut school COVID outbreaks 3.5X

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Enlarge / A second-grade teacher talks to her class during the first day of school at Tustin Ranch Elementary School in Tustin, CA on Wednesday, August 11, 2021.

Schools with universal masking were 3.5 times less likely to have a COVID-19 outbreak and saw rates of child COVID-19 cases 50 percent lower in their counties compared with schools without mask requirements. That’s according to two new studies published Friday by the Centers for Disease Control and Prevention.

The new data lands as masks continue to be a political and social flash point in the US. And children—many of whom are still ineligible for vaccination—have headed back into classrooms.

In one of the newly published studies, health researchers in Arizona looked at schools with and without mask policies in Maricopa and Pima Counties. Together, the counties account for more than 75 percent of the state’s population. The researchers identified 210 schools that had universal masking requirements from the start of their school years. They compared those to 480 schools that had no mask requirements throughout the study period, which ran from July 15 to August 30.

The researchers tallied 129 school-associated COVID-19 outbreaks in all of those schools during the study period. About 87.5 percent of the outbreaks were in schools without mask requirements. The researchers then ran an analysis, adjusting for school sizes, COVID-19 case rates in each school’s zip code, socioeconomics measures, and other factors. The researchers found that the odds of a school-associated COVID-19 outbreak were 3.5 times higher in the schools without mask requirements compared to those with universal masking.

In a separate study, CDC researchers tried to assess if schools’ mask policies have broader impacts for their communities—and they do. The researchers looked at county-level data on the rates of pediatric COVID-19 cases in 520 counties around the US. They compared rates of child COVID-19 cases in the week before and week after schools started their terms.

Though all counties generally saw increases in pediatric COVID-19 cases after schools started up, the counties with universally masked schools saw smaller bumps. For counties with school mask requirements, the average increase in case rates after schools started was 16.32 cases per 100,000 children per day. Counties without school mask requirements saw an average rate increase about twice as high—34.85 cases per 100,000 children per day.

Mask safety

The US continues to see a patchwork of mask use and other protective measures in schools as the 2021-2022 school year gets underway. Many schools in many states do not have universal masking requirements even though the CDC and the American Academy of Pediatrics both recommend universal masking in schools. In some states state leaders have prohibited schools from issuing mask requirements—and even penalized them for requiring masks.

Florida Governor Ron DeSantis is among the leaders who have banned mask mandates in schools. And, although the ban is being challenged in court, DeSantis is withholding money from school boards that have issued mask mandates anyway.

On Thursday, the US Department of Education announced that it had granted the school board of Florida’s Alachua County $147,719. The money is intended to “restore funding withheld by state leaders—such as salaries for school board members or superintendents who have had their pay cut—when a school district implemented strategies to help prevent the spread of COVID-19 in schools.”

In a statement, Alachua County Public School Superintendent Dr. Carlee Simon: “I’m very grateful to [US Secretary of Education Miguel] Cardona, President Biden and the federal government for the funding. But I’m even more grateful for their continued support and encouragement of our efforts to protect students and staff and to keep our schools open for in-person learning.”

Alachua is the first county in the nation to receive such funding, provided through the new Project to Support America’s Families and Educators (Project SAFE) grant program.

In a separate statement, education secretary Cardona said: “We should be thanking districts for using proven strategies that will keep schools open and safe, not punishing them. We stand with the dedicated educators in Alachua and across the country doing the right thing to protect their school communities.”

Public health experts say that masks are a critical tool to help protect children, teachers, and staff from the spread of the pandemic coronavirus, SARS-CoV-2. Masks are intended to be one key layer of a multi-layered approach that also includes vaccination for those eligible, physical distancing when possible, improved ventilation, testing, quarantining, improved hygiene, and disinfection and cleaning.

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NASA seeks a new ride for astronauts to the Artemis launch pad

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Enlarge / NASA first began using the 1983-model Airstream for space shuttle missions in 1984.

NASA

NASA has asked industry for ideas to develop an “Artemis Crew Transportation Vehicle” that will take its astronauts from suit-up facilities to the launch pad on launch day.

The space agency, of course, has not launched its own astronauts on a NASA-built vehicle since the end of the space shuttle program in 2011. From 1984 through the end of the shuttle era, the agency used a modified Airstream motor home, known as the “Astrovan,” to ferry crews to the launch pad. This iconic vehicle had a shiny, silvery exterior but a fairly spartan interior. “The current vehicle’s appeal is rooted in its tradition rather than its décor,” the agency acknowledged in 2011.

Now, NASA is gearing up for a new era of deep space exploration, and it plans to launch four astronauts at a time inside the Orion spacecraft, on top of a Space Launch System rocket. The first human flights on these vehicles could occur in late 2023 or early 2024, NASA administrator Bill Nelson recently said.

While it has taken literally decades and tens of billions of dollars to develop the spacecraft and rocket, NASA is hoping its launch pad ride can be furnished a little more quickly. In its solicitation, released Friday, NASA says its “Artemis CTV” should be delivered no later than June 2023.

NASA is considering three different options for the new vehicle. A provider can custom-build a vehicle, modify a commercially available vehicle, or repair and refurbish the venerable Astrovan.

As part of its solicitation, NASA has a lengthy list of requirements for its Artemis transport vehicle. Among them:

  • It must be a zero-emission vehicle, such as battery-electric, plug-in hybrid electric, or fuel cell electric
  • It must have a carrying capacity of eight passengers, including four fully suited astronauts
  • It must have extensive capacity for equipment, including large bags for helmets, ice-based cooling units, and more
  • Have sufficiently wide doors of 24 to 36 inches for ingress and egress by suited astronauts

According to Ars automotive editor Jonathan Gitlin, it is unlikely that any existing zero-emissions vehicle meets these requirements, even with modifications. Ford’s forthcoming electric Transit Van may come close, Gitlin added.

NASA astronauts Doug Hurley, Chris Ferguson, and Sandy Magnus inside the Astrovan in 2011.
Enlarge / NASA astronauts Doug Hurley, Chris Ferguson, and Sandy Magnus inside the Astrovan in 2011.

NASA

The best option, in fact, may be renovating the old Airstream. This is because the vehicle will not be called upon for particularly long journeys—it’s only a few kilometers to and from the launch pad—and this demand would be well within the capabilities of a couple Tesla drive units and a slab of batteries.

With the Artemis program, NASA is going back to the Moon like it did in the 1960s. It’s using a capsule design, not dissimilar to Apollo, and a large rocket with space shuttle main engines designed in the 1970s. So, why shouldn’t astronaut transport be retro, too?

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CDC director overrules experts, allows Pfizer boosters for health workers

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Enlarge / CDC Director Rochelle Walensky testifies during a Senate committee hearing in July 2021.

Just past midnight last night, the director of the Centers for Disease Control and Prevention overruled a committee of independent advisers, allowing for use of a Pfizer/BioNTech vaccine booster dose in people with increased risk of occupational and institutional exposure to the pandemic coronavirus. That includes health care workers, front-line workers, teachers, day care providers, grocery store workers, and people who work or live in prisons and homeless shelters, among others.

Hours earlier, the CDC’s Advisory Committee on Immunization Practices (ACIP) concluded a two-day meeting on booster recommendations—and voted 9-6 against recommending boosters for this group.

“As CDC Director, it is my job to recognize where our actions can have the greatest impact,” Director Rochelle Walensky said in a statement. “At CDC, we are tasked with analyzing complex, often imperfect data to make concrete recommendations that optimize health. In a pandemic, even with uncertainty, we must take actions that we anticipate will do the greatest good.”

She further noted that the inclusion of people at high risk of COVID-19 from occupational and institutional exposure “aligns with the FDA’s booster authorization.” The Food and Drug Administration last Wednesday issued an amended Emergency Use Authorization for the Pfizer/BioNTech vaccine, which allowed booster doses for people 65 and older as well as people ages 18 to 64 who are at high risk of COVID-19 either from underlying medical conditions or occupational and institutional exposures.

Though the CDC’s advisory committee was torn over endorsing that use, they ultimately decided that the need was not there—vaccine effectiveness against severe disease and hospitalization remains very strong in those under age 65. And recommending boosters for anyone with a conceivable occupational or institutional risk could create a booster free-for-all.

By taking the unusual move to overrule the ACIP’s decisions, Walensky puts the booster efforts more in line with the Biden administration’s preliminary plans to offer booster doses to all vaccinated adults, starting this week.

Still, the current recommendations only apply to the Pfizer/BioNTech vaccine and those who received that vaccine for their two-dose “primary series.” Those who initially received two doses of the Moderna COVID-19 vaccine or one shot of Johnson & Johnson’s vaccine are advised to wait for further booster data and recommendations.

For now, here are the CDC’s official recommendations of who should get a Pfizer/BioNTech vaccine booster—to be given at least six months after the primary Pfizer/BioNTech series. (Emphasis added by CDC).

  • people 65 years and older and residents in long-term care settings should receive a booster shot of Pfizer-BioNTech’s COVID-19 vaccine at least 6 months after their Pfizer-BioNTech primary series,
  • people ages 50–64 years with underlying medical conditions should receive a booster shot of Pfizer-BioNTech’s COVID-19 vaccine at least 6 months after their Pfizer-BioNTech primary series,
  • people ages 18–49 years with underlying medical conditions may receive a booster shot of Pfizer-BioNTech’s COVID-19 vaccine at least 6 months after their Pfizer-BioNTech primary series, based on their individual benefits and risks, and
  • people ages 18-64 years who are at increased risk for COVID-19 exposure and transmission because of occupational or institutional setting may receive a booster shot of Pfizer-BioNTech’s COVID-19 vaccine at least 6 months after their Pfizer-BioNTech primary series, based on their individual benefits and risks.
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