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How DART Scientists Know the Experiment to Shove an Asteroid Actually Worked

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LICIACube image showing the plumes of debris streaming from Dimorphos shortly after the DART impact on September 26. “Each rectangle represents a different level of contrast in order to better see fine structure in the plumes,” according to the European Space Agency.
Image: ASI/NASA/APL

Earlier this week, NASA announced that its DART spacecraft successfully moved an asteroid by a few dozen feet. This raises a valid question: How the heck did scientists figure this out, given that Dimorphos is nearly 7 million miles away? Needless to say, this task required some clever astronomy and a veritable village of astronomers.

NASA’s Double Asteroid Redirection Test, or DART, shortened the amount of time it takes Dimorphos to orbit Didymos, as the spacecraft pushed the target asteroid slightly closer to its larger companion. Dimorphos’s orbital period around Didymos used to be 11 hours and 55 minutes, but it’s now 11 hours and 23 minutes—a change of 32 minutes, give or take two minutes. That represents “tens of meters” in terms of the altered distance, as Nancy Chabot, DART coordination lead at the Johns Hopkins Applied Physics Laboratory, told reporters on Tuesday.

A ‘watershed moment’

Speaking at the same press briefing, NASA administrator Bill Nelson described the successful test as a “watershed moment for humanity.” Indeed, it marks the first time that our species has purposefully changed the motion of a celestial object. Critically, it’s also the first full-scale demonstration of an asteroid deflection strategy, one that could eventually protect us from a bona fide asteroid threat.

See more on this story: Why DART is the most important mission ever launched to space

Dimorphos doesn’t endanger Earth, but it did offer an ideal platform for testing kinetic impactor technology. The 1,340-pound DART spacecraft, following a 10-month journey to the binary asteroid system, plowed into the 525-foot-wide (160-meter) asteroid at speeds reaching 14,000 miles per hour (22,500 kilometers per hour). DART struck the asteroid with razor-like precision on September 26, but it wasn’t immediately obvious if the impact had any kind of effect.

A Hubble Space Telescope image showing the binary asteroid system shortly after the impact on September 26. The test triggered the formation of a comet-like tail composed of Sun-blown dust.
A Hubble Space Telescope image showing the binary asteroid system shortly after the impact on September 26. The test triggered the formation of a comet-like tail composed of Sun-blown dust.
Image: NASA/ESA/STScI/Hubble

That the $308 million DART test did something to the unsuspecting asteroid was immediately obvious, with both space-based and ground-based observations revealing a dramatic plume and comet-like tail in the hours and days following the impact. It took about two weeks, however, for astronomers to confirm the new orbital dynamics imposed upon the Didymos-Dimorphos system. Two separate datasets were needed for the task, one optical and the other radar, but both pointed to the same answer: 11 hours and 23 minutes.

Catching an altered eclipse

Optical data came from ground-based observatories around the world, including the Las Cumbres Observatory (LCO) telescopes in South Africa and the Southern Astrophysical Research Telescope in Chile. A limitation of optical telescopes is that, due to the distance and small size of the Didymos-Dimorphous system, the two objects are seen as a single glowing dot. The asteroids are just 0.75 miles (1.2 km) apart, with Didymos, the larger of the two, measuring just 2,560 feet (780 meters) wide.

Ground-based optical telescopes can’t distinguish between the two, but that doesn’t mean Dimorphos is invisible to these eyes. The brightness of Didymos temporarily drops by around 10% each time Dimorphos passes in front of it. It’s through these clock-work eclipses that astronomers knew Dimorphos’s orbital period prior to the test and how they’re able to determine it now. That Dimorphos passes in front of Didymos from our perspective on Earth is fortuitous, and a key reason for why this system was chosen for the DART test.

The DART team studied reductions in brightness caused by Dimorphos’s eclipses of Didymos.
The DART team studied reductions in brightness caused by Dimorphos’s eclipses of Didymos.
Image: NASA/Johns Hopkins APL/Astronomical Institute of the Academy of Sciences of the Czech Republic/Lowell Observatory/JPL/Las Cumbres Observatory/Las Campanas Observatory/European Southern Observatory Danish (1.54-m) telescope/University of Edinburgh/The Open University/Universidad Católica de la Santísima Concepción/Seoul National Observatory/Universidad de Antofagasta/Universität Hamburg/Northern Arizona University.

Optical observatories across the world performed continuous observations over hours-long timescales. “Since the [orbital] period was close to 12 hours, having telescopes in South Africa roughly six hours away from Chile meant we could capture the other times when Dimorphos went behind or in front of Didymos we couldn’t see from Chile,” Tim Lister, an astronomer with LCO, explained in a South African Astronomical Observatory press release. “This really helped nail down the new period and the amount of change caused by the DART impact.”

Detecting ‘faint radar echoes’

The radar data came from NASA JPL’s Goldstone planetary radar in California and the NSF’s Green Bank Observatory in West Virginia. Unlike optical telescopes, radar “can get distinct signals from both objects directly,” said Chabot.

Radar imagery from the two observatories, taken each night during a two-week campaign, were combined to create before-and-after views of the binary asteroid system. This allowed astronomers to measure the “difference between where Dimorphos is observed compared to where it would have been with the original orbit,” as NASA explained in its press package.

In this radar image, the green circle shows the location of Dimorphos around the larger Didymos asteroid, seen as the bright line across the middle of the images. The blue circle shows where Dimorphos would’ve been had the DART experiment not happened.
In this radar image, the green circle shows the location of Dimorphos around the larger Didymos asteroid, seen as the bright line across the middle of the images. The blue circle shows where Dimorphos would’ve been had the DART experiment not happened.
Image: NASA/Johns Hopkins APL/JPL/NASA JPL Goldstone Planetary Radar/National Science Foundation’s Green Bank Observatory

“The Green Bank Telescope’s large collecting area makes it extremely sensitive and a prime receiving station to detect these faint radar echoes,” Jim Jackson, director of the Green Bank Observatory, explained in a statement. “These radar measurements” were key to determining “just how dramatic the event really was by sensing changes in its orbit around Didymos and definitively establishing its deflection.”

The “two independent methods” provided “the same answer,” said Chabot, in reference to Dimorphos’s new 11 hour and 23 minute orbital period. She credited the international team for getting “onto this very quickly.” But plenty of work remains.

The beginning of the beginning

Indeed, much is unknown about the effect of the experiment. DART was a rousing success, but it’s clear that scientists still have lots to learn about kinetic impactors and the art of deflecting asteroids.

For example, astronomers need to refine their estimates of Dimorphos’s mass, shape, density, and surface composition. This will help them to understand how the DART spacecraft transferred its momentum into its target and how the ensuing effects contributed to the observed orbital shift.

Dimorphos, as imaged by the DRACO instrument aboard the DART spacecraft.
Dimorphos, as imaged by the DRACO instrument aboard the DART spacecraft.
Image: NASA/Johns Hopkins APL

During Tuesday’s press briefing, Tom Statler, DART program scientist at NASA, said the recoil from the debris blasting off the surface was a major contributor to the orbital change. This is likely a consequence of Dimorphos’s physical makeup as a rubble pile asteroid, as opposed to it being a compact and cohesive rock. Statler also wondered if Dimorphos is now wobbling as a result of the impact. Astronomers are keeping a close watch on the system to refine their preliminary estimates and observe any further changes to the binary pair.

The European Space Agency is planning a follow-up mission to visit the asteroids up-close. The HERA probe, scheduled to launch in 2024, will observe Dimorphos in late 2026 and send back images and other data to help us better understand the effects of DART. A robust planetary defense system against asteroids won’t be built overnight, but this important work has now started in earnest.

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Here’s how Helene and other storms dumped a whopping 40 trillion gallons of rain on the South

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More than 40 trillion gallons of rain drenched the Southeast United States in the last week from Hurricane Helene and a run-of-the-mill rainstorm that sloshed in ahead of it — an unheard of amount of water that has stunned experts.

That’s enough to fill the Dallas Cowboys’ stadium 51,000 times, or Lake Tahoe just once. If it was concentrated just on the state of North Carolina that much water would be 3.5 feet deep (more than 1 meter). It’s enough to fill more than 60 million Olympic-size swimming pools.

“That’s an astronomical amount of precipitation,” said Ed Clark, head of the National Oceanic and Atmospheric Administration’s National Water Center in Tuscaloosa, Alabama. “I have not seen something in my 25 years of working at the weather service that is this geographically large of an extent and the sheer volume of water that fell from the sky.”

The flood damage from the rain is apocalyptic, meteorologists said. More than 100 people are dead, according to officials.

Private meteorologist Ryan Maue, a former NOAA chief scientist, calculated the amount of rain, using precipitation measurements made in 2.5-mile-by-2.5 mile grids as measured by satellites and ground observations. He came up with 40 trillion gallons through Sunday for the eastern United States, with 20 trillion gallons of that hitting just Georgia, Tennessee, the Carolinas and Florida from Hurricane Helene.

Clark did the calculations independently and said the 40 trillion gallon figure (151 trillion liters) is about right and, if anything, conservative. Maue said maybe 1 to 2 trillion more gallons of rain had fallen, much if it in Virginia, since his calculations.

Clark, who spends much of his work on issues of shrinking western water supplies, said to put the amount of rain in perspective, it’s more than twice the combined amount of water stored by two key Colorado River basin reservoirs: Lake Powell and Lake Mead.

Several meteorologists said this was a combination of two, maybe three storm systems. Before Helene struck, rain had fallen heavily for days because a low pressure system had “cut off” from the jet stream — which moves weather systems along west to east — and stalled over the Southeast. That funneled plenty of warm water from the Gulf of Mexico. And a storm that fell just short of named status parked along North Carolina’s Atlantic coast, dumping as much as 20 inches of rain, said North Carolina state climatologist Kathie Dello.

Then add Helene, one of the largest storms in the last couple decades and one that held plenty of rain because it was young and moved fast before it hit the Appalachians, said University of Albany hurricane expert Kristen Corbosiero.

“It was not just a perfect storm, but it was a combination of multiple storms that that led to the enormous amount of rain,” Maue said. “That collected at high elevation, we’re talking 3,000 to 6000 feet. And when you drop trillions of gallons on a mountain, that has to go down.”

The fact that these storms hit the mountains made everything worse, and not just because of runoff. The interaction between the mountains and the storm systems wrings more moisture out of the air, Clark, Maue and Corbosiero said.

North Carolina weather officials said their top measurement total was 31.33 inches in the tiny town of Busick. Mount Mitchell also got more than 2 feet of rainfall.

Before 2017’s Hurricane Harvey, “I said to our colleagues, you know, I never thought in my career that we would measure rainfall in feet,” Clark said. “And after Harvey, Florence, the more isolated events in eastern Kentucky, portions of South Dakota. We’re seeing events year in and year out where we are measuring rainfall in feet.”

Storms are getting wetter as the climate change s, said Corbosiero and Dello. A basic law of physics says the air holds nearly 4% more moisture for every degree Fahrenheit warmer (7% for every degree Celsius) and the world has warmed more than 2 degrees (1.2 degrees Celsius) since pre-industrial times.

Corbosiero said meteorologists are vigorously debating how much of Helene is due to worsening climate change and how much is random.

For Dello, the “fingerprints of climate change” were clear.

“We’ve seen tropical storm impacts in western North Carolina. But these storms are wetter and these storms are warmer. And there would have been a time when a tropical storm would have been heading toward North Carolina and would have caused some rain and some damage, but not apocalyptic destruction. ”

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Follow AP’s climate coverage at https://apnews.com/hub/climate

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Follow Seth Borenstein on Twitter at @borenbears

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Associated Press climate and environmental coverage receives support from several private foundations. See more about AP’s climate initiative here. The AP is solely responsible for all content.

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‘Big Sam’: Paleontologists unearth giant skull of Pachyrhinosaurus in Alberta

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It’s a dinosaur that roamed Alberta’s badlands more than 70 million years ago, sporting a big, bumpy, bony head the size of a baby elephant.

On Wednesday, paleontologists near Grande Prairie pulled its 272-kilogram skull from the ground.

They call it “Big Sam.”

The adult Pachyrhinosaurus is the second plant-eating dinosaur to be unearthed from a dense bonebed belonging to a herd that died together on the edge of a valley that now sits 450 kilometres northwest of Edmonton.

It didn’t die alone.

“We have hundreds of juvenile bones in the bonebed, so we know that there are many babies and some adults among all of the big adults,” Emily Bamforth, a paleontologist with the nearby Philip J. Currie Dinosaur Museum, said in an interview on the way to the dig site.

She described the horned Pachyrhinosaurus as “the smaller, older cousin of the triceratops.”

“This species of dinosaur is endemic to the Grand Prairie area, so it’s found here and nowhere else in the world. They are … kind of about the size of an Indian elephant and a rhino,” she added.

The head alone, she said, is about the size of a baby elephant.

The discovery was a long time coming.

The bonebed was first discovered by a high school teacher out for a walk about 50 years ago. It took the teacher a decade to get anyone from southern Alberta to come to take a look.

“At the time, sort of in the ’70s and ’80s, paleontology in northern Alberta was virtually unknown,” said Bamforth.

When paleontogists eventually got to the site, Bamforth said, they learned “it’s actually one of the densest dinosaur bonebeds in North America.”

“It contains about 100 to 300 bones per square metre,” she said.

Paleontologists have been at the site sporadically ever since, combing through bones belonging to turtles, dinosaurs and lizards. Sixteen years ago, they discovered a large skull of an approximately 30-year-old Pachyrhinosaurus, which is now at the museum.

About a year ago, they found the second adult: Big Sam.

Bamforth said both dinosaurs are believed to have been the elders in the herd.

“Their distinguishing feature is that, instead of having a horn on their nose like a triceratops, they had this big, bony bump called a boss. And they have big, bony bumps over their eyes as well,” she said.

“It makes them look a little strange. It’s the one dinosaur that if you find it, it’s the only possible thing it can be.”

The genders of the two adults are unknown.

Bamforth said the extraction was difficult because Big Sam was intertwined in a cluster of about 300 other bones.

The skull was found upside down, “as if the animal was lying on its back,” but was well preserved, she said.

She said the excavation process involved putting plaster on the skull and wooden planks around if for stability. From there, it was lifted out — very carefully — with a crane, and was to be shipped on a trolley to the museum for study.

“I have extracted skulls in the past. This is probably the biggest one I’ve ever done though,” said Bamforth.

“It’s pretty exciting.”

This report by The Canadian Press was first published Sept. 25, 2024.

The Canadian Press. All rights reserved.

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The ancient jar smashed by a 4-year-old is back on display at an Israeli museum after repair

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TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.

Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.

Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.

The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.

The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.

It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.

Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.

Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.

Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.

Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.

Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.

The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”

The Canadian Press. All rights reserved.

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