Science
Watch the Chelyabinsk Meteor Breakup in this Detailed Simulation
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The people of Chelyabinsk in Russia got the surprise of their lives on the morning of February 15, 2013. That’s when a small asteroid exploded overhead. The resulting shockwave damaged buildings, injured people, and sent a sonic boom thundering across the region.
The Chelyabinsk impactor was about 20 meters across. It broke up in the atmosphere in an airburst and sent a shower of debris across the landscape. The event awakened people to the dangers of incoming space debris. Since we experience frequent warnings about near-Earth objects, scientists want to understand what a piece of space rock can do.
These days, there are many observation programs across the planet. For example, NASA operates its Sentry System and ESA sponsors the NEODyS project. They and others track incoming space rock. The observation data help predict the impacts of all but the very smallest asteroid chunks that come our way. Despite those programs, it’s inevitable that something like the Chelyabinsk asteroid chunk will slip through. So, it’s important to understand what happens during such an impact.
Modeling the Chelyabinsk Meteor
Scientists around the world began studying the event almost as soon as it happened. They collected bits of the debris and studied images of the entire event. Researchers with the Planetary Defense program at the Lawrence Livermore National Laboratory recently released a highly detailed 3D animation of a simulated chunk of space rock modeled after the Chelyabinsk impactor. They based the materials of the object in their animation on meteorites recovered from the ground.
Because people recorded the event with cell phones and security cameras, the team compared their model to what everybody witnessed. It turned out to be very close to what actually happened.
“This is something that can really only be captured with 3D simulation,” said Jason Pearl, lead researcher on the project. “When you combine LLNL’s specialized expertise in impact physics and hydrocodes with the Lab’s state-of-the-art High Performance Computing capabilities, we were uniquely positioned to model and simulate the meteor in full 3D. Our research underlines the importance of using these types of high-fidelity models to understand asteroid airburst events. A lot of smaller asteroids are rubble piles or loosely bound collections of space gravel, so the possibility of a monolith is really interesting.”
So, How Did the Chelyabinsk Object Shatter?
The most often-asked question about the rock that smacked into Earth over Russia was: was it a single chunk of debris? Or was it a flying rubble pile? If it was a monolithic chunk of rock, that would imply specific details about the strength of the rock and how it broke up. If it was a flying rubble pile, it might have broken up earlier and higher in the atmosphere. The LLNL experiment implies strongly that the impact was a single monolithic rock. It broke up under the heat and pressure of atmospheric entry.
To model the impactor and its behavior, the research team used a computational method called “smoothed particle hydrodynamics (SPH).” It models an object in a fluidic flow. In this case, it treats the atmosphere as a fluid. The model also simulates what happens as a Chelyabinsk-sized hunk of rock moves through the simulated air.
In their simulation, the team found that the incoming object started to break up from the rear and the cracks moved from back to front. The timescale of crack propagation toward the front of the asteroid controls the time at which the asteroid splits into smaller fragments while entering Earth’s atmosphere. A collection of fragments lies near the shock front and that shields the rest of the fragmenting rock. Finally, when the impactor reaches about 30 kilometers above Earth’s surface, intact fragments separate. That’s when the debris is exposed to the free stream. Eventually, the debris cloud decelerates very quickly and the remaining fragments continue to break up as they fly through the air toward the ground.
The Physics of the Breakup
The disintegration of the Chelyabinsk object provided scientists with a “physics-rich” event to study. According to LLNL physicist Mike Owen, the coupling of the asteroid to the atmosphere depends on how much surface area it has. The greater the surface area, the more exposure it has to heat, stress and pressure. Those all combine to break it up.
“As the asteroid enters the atmosphere, you start to have sort of a catastrophic failure,” Owen said. “And it tends to compress in the direction of travel. It was like the asteroid was being squeezed in the direction of travel, breaking into distinct pieces that started to separate and break perpendicular to the direction of travel. All of a sudden, you’ve got a lot more material being exposed to the hypersonic interaction with the air, a lot more heat being dumped in, a lot more stress on it, which makes it break faster and you get sort of a cascading runaway process.”
Using Chelyabinsk To Understand Future Impacts
Models of impactors like this one provide insight into future events when chunks of space rock will hit Earth. One long-term goal would be to use such models to assess what will happen to a target region during an impact. Meteoric impacts are natural disasters that affect our planet just as fires and floods do. As such, there’s a need to predict and understand them so that people can be more prepared.
Researcher Cody Raskin points to our increased ability to detect such incoming impactors. “If we can see a small asteroid approaching Earth in time, we could run our model and inform authorities of the potential risk, similar to a hurricane map,” said Raskin. “They could then take appropriate protective actions, such as evacuating residents or issuing shelter-in-place orders, ultimately saving lives.”
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SASKATOON – Saskatchewan engineering students will have their eyes on the sky as the province’s first homegrown satellite is to be launched on board a SpaceX rocket headed for the International Space Station.
“I am so excited about it,” said Rylee Moody, a third-year student at the University of Saskatchewan.
“It’s something I would never have dreamed of doing.”
Engineering students at the University of Saskatchewan spent five years developing the cube satellite called RADSAT-SK. It is set to be launched into space Saturday.
RADSAT-SK will be sent into its own orbit for a year, where it will collect radiation data that will be analyzed at a ground station located near the university’s campus.
The project was part of a Canadian Space Agency project that saw 15 universities get grants to build CubeSats — cubical, standard-sized miniature satellites that generally weigh about a kilogram.
Sean Maw, a principal investigator and chair in innovative teaching at the College of Engineering, said Saskatchewan’s project began in 2018 with about 20 engineering undergraduate students. Since then, hundreds of students have put in tens of thousands of hours to ensure ideas became reality.
It was no easy task to get from a satellite concocted in a Saskatchewan university to infinity and beyond. Students designed, built, tested and integrated the satellite.
They also navigated the complicated international regulatory environment to get it approved for launch. A global pandemic certainly didn’t make it easier, Maw added.
“Students persevered through the whole COVID crisis to get this project done,” Maw said. “Especially in the last 12 months or so they fought tooth and nail to get RADSAT-SK to the finish line.”
The team came up with a motto to get through the tough times: fail hard, fail fast, recover.
The satellite’s payload, what it carries as it orbits earth, is focused on radiation research. A Saskatchewan-made dosimeter board will measure radiation from space and a fungal melanin coating on board will test the feasibility of the polymer to shield space radiation.
Arliss Sidlowksi, a fourth-year student, said it has been an incredible and challenging experience getting the satellite ready for orbit.
“I am so proud of our team for their resilience,” she said.
“We experienced numerous challenges over the years. Our members viewed each setback as an opportunity to learn, adapt and proving time and time again their perseverance and intelligence.”
Sidlowksi said she hopes it will inspire other students to see themselves working in the space industry while also showing the rest of the country what Saskatchewan has to offer.
“I think it’s really opening up Saskatchewan to the space sector.”
It’s very important students have the support to dream for the stars, Maw added. Decades ago when he was getting his undergraduate degree at the University of Waterloo he brought a group of students together to build a satellite.
The project wasn’t supported. And the satellite never got off ground.
“I wasn’t going to let that happen to these guys,” Maw said.
“Their efforts were truly remarkable.”
This report by The Canadian Press was first published May 29, 2023.
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A flat, rounded shell. A tail that’s folded under the body. This is what a crab looks like, and apparently what peak performance might look like — at least according to evolution. A crab-like body plan has evolved at least five separate times among decapod crustaceans, a group that includes crabs, lobsters and shrimp. In fact, it’s happened so often that there’s a name for it: carcinization.
So why do animals keep evolving into crab-like forms? Scientists don’t know for sure, but they have lots of ideas.
Carcinization is an example of a phenomenon called convergent evolution, which is when different groups independently evolve the same traits. It’s the same reason both bats and birds have wings. But intriguingly, the crab-like body plan has emerged many times among very closely related animals.
The fact that it’s happening at such a fine scale “means that evolution is flexible and dynamic,” Javier Luque, a senior research associate in the Department of Zoology at the University of Cambridge, told Live Science.
Related: Does evolution ever go backward?
Crustaceans have repeatedly gone from having a cylindrical body plan with a big tail — characteristic of a shrimp or a lobster — to a flatter, rounder, crabbier look, with a much less prominent tail. The result is that many crustaceans that resemble crabs, like the tasty king crab that’s coveted as a seafood delicacy, aren’t even technically “true crabs.” They’ve adopted a crab-like body plan, but actually belong to a closely related group of crustaceans called “false crabs.”
When a trait appears in an animal and sticks around through generations, it’s a sign that the trait is advantageous for the species — that’s the basic principle of natural selection. Animals with crabby forms come in many sizes and thrive in a wide array of habitats, from mountains to the deep sea. Their diversity makes it tricky to pin down a single common benefit for their body plan, said Joanna Wolfe, a research associate in organismic and evolutionary biology at Harvard University.
Wolfe and colleagues laid out a few possibilities in a 2021 paper in the journal BioEssays. For example, crabs’ tucked-in tail, versus the lobster’s much more prominent one, could reduce the amount of vulnerable flesh that’s accessible to predators. And the flat, rounded shell could help a crab scuttle sideways more effectively than a cylindrical lobster body would allow.
But more research is needed to test those hypotheses, Wolfe said. She is also trying to use genetic data to better understand the relationships among different decapod crustaceans, to more accurately pinpoint when various “crabby” lineages evolved, and pick apart the factors driving carcinization.
There’s another possible explanation: “It’s possible that having a crab body isn’t necessarily advantageous, and maybe it’s a consequence of something else in the organism,” Wolfe said. For example, the crab body plan might be so successful not because of the shell or tail shape itself, but because of the possibilities that this shape opens up for other parts of the body, said Luque, who is a co-author of the 2021 paper with Wolfe.
For example, a lobster’s giant tail can propel the animal through the water and help it crush prey. But it can also get in the way and constrain other features, Luque said. The crab body shape might leave more flexibility for animals to evolve specialized roles for their legs beyond walking, allowing crabs to easily adapt to new habitats. Some crabs have adapted their legs for digging under sediment or paddling through water.
“We think that the crab body plan has evolved so many times independently because of the versatility that the animals have,” Luque said. “That allows them to go places that no other crustaceans have been able to go.”
The crab-like body plan also has been lost multiple times over evolutionary time — a process known as decarcinization.
“Crabs are flexible and versatile,” Luque explained. “They can do a lot of things back and forth.”
Wolfe thinks of crabs and other crustaceans like Lego creations: They have many different components that can be swapped out without dramatically changing other features. So it’s relatively straightforward for a cylindrical body to flatten out, or vice versa. But for better or worse, humans won’t be turning into crabs anytime soon. “Our body isn’t modular like that,” Wolfe said. “[Crustaceans] already have the right building blocks.”
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Ibadan, 29 May 2023. – Rocket Lab USA, Inc. has successfully completed the second of two dedicated Electron launches to deploy a constellation of tropical cyclone monitoring satellites for NASA. The “Coming To A Storm Near You” launch lifted off on May 26 at 15:46 NZST (03:46 UTC) from Rocket Lab Launch Complex 1 on New Zealand’s Mahia Peninsula, deploying the final two CubeSats of NASA’s TROPICS constellation to orbit.
“Coming To A Storm Near You” is Rocket Lab’s second of two TROPICS launches for NASA, following the first launch on May 8th NZST. Like the previous launch, “Coming To A Storm Near You” deployed a pair of shoebox-sized satellites to low Earth orbit to collect tropical storm data more frequently than other weather satellites. The constellation aims to help increase understanding of deadly storms and improve tropical cyclone forecasts.
Rocket Lab has now launched all four satellites across two dedicated launches within 18 days, enabling the TROPICS satellites to settle into their orbits and begin commissioning ahead of the 2023 North American storm season, which begins in June.
“Electron was for exactly these kinds of missions – to deploy spacecraft reliably and on rapid timelines to precise and bespoke orbits, so we’re proud to have delivered that for NASA across both TROPICS launches and meet the deadline for getting TROPICS to orbit in time for the 2023 storm season,” said Rocket Lab founder and CEO Peter Beck. “Thank you to the team at NASA for entrusting us with such an important science mission, we’re grateful to be your mission launch providers once again.”
‘Coming To A Storm Near You’ was Rocket Lab’s fifth mission for 2023 and the Company’s 37th Electron mission overall. It brings the total number of satellites launched into orbit by Rocket Lab to 163.
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