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Could we really deflect an asteroid heading for Earth? An expert explains NASA's latest DART mission – Phys.Org

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Small asteroid impacts showing day-time impacts (in yellow) and night-time impacts (in blue). The size of each dot is proportional to the optical radiated energy of the impact. Credit: NASA JPL

A NASA spacecraft the size of a golf cart has been directed to smash into an asteroid, with the intention of knocking it slightly off course. The test aims to demonstrate our technological readiness in case an actual asteroid threat is detected in the future.

The Double Asteroid Redirection Test (DART) lifted off aboard a SpaceX rocket from California on November 23, and will arrive at the target asteroid system in September, next year.

The mission will travel to the asteroid Didymos, a member of the Amor group of asteroids. Every 12 hours Didymos is orbited by a mini-moon, or “moonlet”, Dimorphos. This smaller half of the pair will be DART’s target.

Are we facing an extinction threat from asteroids?

We’ve all seen disaster movies in which an asteroid hits Earth, creating an similar to the one that killed off the dinosaurs millions of years ago. Could that happen now?

Well, Earth is actually bombarded frequently by small asteroids, ranging from 1-20 metres in diameter. Almost all asteroids of this size disintegrate in the atmosphere and are usually harmless.

There is an inverse relationship between the size of these object and the frequency of impact events. This means we get hit much more frequently by small objects than larger ones—simply because there are many more smaller objects in space.

Asteroids with a 1km diameter strike Earth every 500,000 years, on average. The most “recent” impact of this size is thought to have formed the Tenoumer impact crater in Mauritania, 20,000 years ago. Asteroids with an approximate 5km diameter impact Earth about once every 20 million years.

The 2013 Chelyabinsk meteoroid, which damaged buildings in six Russian cities and injured around 1,500 people, was estimated to be about 20m in diameter.

This animation shows DART’s trajectory around the Sun. Pink = DART | Green = Didymos | Blue = Earth | Turquoise = 2001 CB21 | Gold = 3361 Orpheus.

Assessing the risk

NASA’s DART mission has been sparked by the threat and fear of a major asteroid hitting Earth in the future.

The Torino scale is a method for categorising the impact hazard associated with a near-Earth object (NEO). It uses a scale from 0 to 10, wherein 0 means there is negligibly small chance of collision, and 10 means imminent collision, with the impacting object being large enough to precipitate a global disaster.

The Chicxulub impact (which is attributed to the extinction of non-avian dinosaurs) was a Torino scale 10. The impacts that created the Barringer Crater, and the 1908 Tunguska event, both correspond to Torino Scale 8.

With the increase of online news and individuals’ ability to film events, asteroid “near-misses” tend to generate fear in the public. Currently, NASA is keeping a close eye on asteroid Bennu, which is the object with the largest “cumulative hazard rating” right now. (You can keep up to date too).

With a 500m diameter, Bennu is capable of creating a 5km crater on Earth. However, NASA has also said there is a 99.943% chance the asteroid will miss us.

Brace for impact

At one point in their orbit around the Sun, Didymos and Dimorphos come within about 5.9 million km of Earth. This is still further away than our Moon, but it’s very close in astronomical terms, so this is when DART will hit Dimorphos.

Could we really deflect an asteroid heading for Earth? An expert explains NASA's latest DART mission
The DART mission dates and timeline events. Credit: Johns Hopkins University

DART will spend about ten months travelling towards Didymos and, when it’s close by, will change direction slightly to crash into Dimorphos at a speed of about 6.6km per second.

The larger Didymos is 780m in diameter and thus makes a better target for DART to aim for. Once DART has detected the much smaller Dimorphos, just 160m in diameter, it can make a last-minute course correction to collide with the moonlet.

The mass of Dimorphos is 4.8 million tonnes and the mass of DART at impact will be about 550kg. Travelling at 6.6km/s, DART will be able to transfer a huge amount of momentum to Dimorphos, to the point where it’s expected to actually change the moonlet’s orbit around Didymos.

This change, to the tune of about 1%, will be detected by ground telescopes within weeks or months. While this may not seem like a lot, 1% is actually a promising shift. If DART were to slam into a lone asteroid, its orbital period around the Sun would change by only about 0.000006%, which would take many years to measure.

So we’ll be able to detect the 1% change from Earth, and meanwhile the pair will continue along its orbit around the Sun. DART will also deploy a small satellite ten days before impact to capture everything.

This is NASA’s first mission dedicated to demonstrating a planetary defence technique. At a cost of US$330 million, it’s relatively cheap in space mission terms. The James Webb Telescope set to launch next month, costs close to US$10 billion.

There will be little to no debris from DART’s impact. We can think of it in terms of a comparable event on Earth; imagine a train parked on the tracks but with no brakes on. Another train comes along and collides with it.

The trains won’t break apart, or destroy one another, but will move off together. The stationary one will gain some speed, and the one impacting it will lose some speed. The trains combine to become a new system with different speeds than before.

So we won’t experience any impact, ripples or debris from the DART mission.

Could we really deflect an asteroid heading for Earth? An expert explains NASA's latest DART mission
Typical asteroid orbits remain between Mars and Jupiter, but some with elliptical orbits can pass close to Earth. Credit: Pearson

Is the effort really worth it?

Results from the mission will tell us just how much mass and speed is needed to hit an asteroid that may pose a threat in the future. We already track the vast majority of asteroids that come close to Earth, so we would have early warning of any such object.

That said, we have missed objects in the past. In October 2021, Asteroid UA_1 passed about 3,047km from Earth’s surface, over Antarctica. We missed it because it approached from the direction of the Sun. At just 1m in size it wouldn’t have caused much damage, but we should have seen it coming.

Building a deflection system for a potential major asteroid threat would be difficult. We would have to act quickly and hit the target with very good aim.

One candidate for such a system could be the new technology developed by the US spaceflight company SpinLaunch, which has designed technology to launch satellites into orbit at rapid speeds. This device could also be used to fire masses at close-passing asteroids.


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Double Asteroid Redirection Test launch could be key step forward in planetary defense


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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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‘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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