Earth’s most recent asteroid hazard brush was eight years ago, when a space rock the size of a six-story building apparently collapsed and injured 1,200 people when it exploded. Chelyabinsk, Russia.
Now scientists use the infamous asteroid this month Apophis to test their responses to potentially dangerous space bricks, with the fine art of planetary defense. Planetary defense focuses on identifying asteroids and comets hanging around the earth, mapping their exact paths and seeing how their orbits compare with the earth.
If an orbital model shows that a asteroid and that the earth must reach the same place at the same time, things become serious, especially when the space rock is large. After all, this is the kind of scenario that ended the dinosaurs’ government. But planetary defenses are not hopeless: if humans identify a dangerous asteroid long enough before impact, we could theoretically do something to divert it.
Related: Scientists prepare for their last good look at asteroid Apophis before 2029
The successful prevention of damage due to an asteroid impact depends on the observation of the threat in time. But although scientists have identified more than 25,000 near-earth asteroids to date, the majority are too small to cause much concern. Although there are many asteroids orbiting the earth, most are not large enough or close enough to cause realistic subsistence.
Apophis gained notoriety because it is not like most of these near-Earth space rocks. When scientists discovered it in 2004, it was immediately noticeable. First, it is relatively large – more than 300 meters wide, around the height of the Eiffel Tower, according to NASA. And models based on early observations suggested that on April 13, 2029, Apophis would collide with nearly 3%.
More accurate observations soon allayed fears of that year’s impact, but the early concerns surrounding the asteroid indicated its name, referring to an Egyptian ‘devil snake personifying evil and chaos’, as NASA put it . At present, scientists are confident that Apophis has not been a threat to Earth for at least a few decades. But the space rock will deliver more visitors next month and offer scientists valuable opportunities to take a closer look at a relatively large asteroid.
And with a little imagination, these flybys can also serve as planetary defense drills.
“The goal is to destroy basically all the scientists from around the world, kind of the coalition of volunteers,” said Vishnu Reddy, an expert in the field of defense at the University of Arizona. coordinating the project, told Space.com. “Then we are going on this months-long campaign to observe this object.”
Related: Large asteroid Apophis flies through Earth on Friday the 13th in 2029, a happy day for scientists
Apophis will fly past Earth on March 5th. The asteroid will remain about a tenth of the average Earth-sun distance away – a straightforward everyday flight compared to the 2029 event, when Apophis will pass at about the height at which especially high satellite orbits.
To celebrate this year, the International Asteroid Warning Network has launched its third such campaign. Previously, scientists on a asteroid named 2012 TC4 and on 1999 KW4, which are a pair of rocks surrounding each other. For Apophis, about 40 scientists from 13 different countries signed. These observers pretend that Apophis has never been seen, which means they start from scratch to evaluate how much danger the asteroid poses to Earth.
‘It is not a scientific purpose“Reddy said.” The aim is to get new observations as if we know nothing about this object and to try to see where we need to improve efficiency in the process and also identify the human factor. Anyone dealing with scientists knows that it’s like caring for cats, and if you do it on an international scale, there’s partly diplomacy, partly science and partly planetary defense. ‘
Reddy said the incident of the Apophis fly occurred during the continuation Covid-19 pandemic provided the opportunity to understand how resilient the asteroid detection system is. At this point, most telescopes manage to continue, though he said the pandemic would likely interfere much more if the fly had occurred a year earlier, when institutions were still scrambling to respond.
“There’s a fair amount of redundancy in planetary defense,” he said. “Even if one telescope goes down or we lose a certain thing, it’s not like the whole community is going down to some degree.”
A “discovery” moment
Campaign members first definitively identified Apophis around December 19, thanks to a space-based tool called NEOWISE. After the spacecraft, originally an astrophysics mission, lost the ability to keep itself cool, scientists rediscovered it to identify new asteroids.
However, the fact that the first discovery credit was awarded to NEOWISE was unusual. Nowadays, most new asteroids are discovered by ground surveys, especially the Pan-STARRS telescopes in Hawaii and the Catalina Sky Survey in Arizona.
But Apophis had a hard time discovering these telescopes on Earth, Reddy said. “The challenge was that the movement and the way it moved was difficult to do with short observation arcs,” he said. NEOWISE is never removed from a target by a rotation of the earth, and since it studies infrared light, it can be observed during the day as well as at night.
“NEOWISE got it first, and it’s because of where we look in the sky and the wavelengths we use to search for it,” Amy Mainzer, an astronomer at the University of Arizona and lead researcher for NEOWISE, told Space .com said. “Getting to Apophis, quote-quote, was really nice.”
There is an advantage to detecting a new asteroid with NEOWISE: the instrument can quickly determine the size of a space rock. Telescopes that identify asteroids using optical light struggle to distinguish between larger dark rocks and smaller light rocks; NEOWISE’s infrared vision removes this confusion.
Related: Defending Earth Against Dangerous Asteroids: Questions and Answers with NASA’s Lindley Johnson
And for this ‘discovery’ of Apophis, the initial optical appearance appears to be more threatening than the calculated diameter of NEOWISE. “You can quickly see if it’s going to be a global disaster or just a region, because you can get the size quickly,” Mainzer said. “It makes a big size difference in predicting danger.”
While a newly discovered asteroid initially has a small chance of impact, additional observations usually increase the chance to nothing. “For Apophis, if you start anew, assuming we know nothing about it and we just discovered it with NEOWISE and we follow it up, there’s a reasonable impact risk of Apophis,” Reddy said.
It is worth emphasizing that ‘reasonable impact risk’ only occurs in the scenario they practice, not in the reality of scientists’ full knowledge of the asteroid. “Of course, if you include the historical observations, it disappears, because we know the orbit very well, it’s not going to hit us,” Reddy said.
Good news for people, but the disappearing impact risk is not helpful for the workout. “This is not what we are looking for, we want to see what the consequences are on the ground,” Reddy said. Thus, at some point, the campaign will become part of reality, and within the safe confines of computer models, scientists will move Apophis to Earth.
By changing the orbit of the asteroid, specialists in planetary defense can practice every phase of the asteroid reaction process, which is actually the point of the campaign.
Continued observations
Apophis has become much easier to observe since his “discovery”; Reddy said amateur astronomers can now see it with a decent perception backyard telescope, and he looks forward to including it in the project.
Meanwhile, the initial hustle and bustle of ‘discovery’ for scientists has subsided somewhat. “There’s a big wave of activity, and then there’s no more in the middle for five or six weeks,” Reddy said. The team, which ignores old data on Apophis, already has much of the information a planetary defense expert would want, data that helps scientists determine the shape or composition of an object.
“The most important event after this point, I think, is the radar observations,” he said; these observations should begin on March 3rd. Planetary radar observations, which reflects a ray of radio waves from an object and then captures the echo, is the most powerful tool that scientists have to study the exact shape and location of an asteroid.
These observations are often the final data scientists need to confirm that an asteroid will pass safely to Earth. The responsibility for the observations will depend on NASA Goldstone Deep Space Communications Complex in California, after December collapse of the radio telescope at Arecibo Observatory in Puerto Rico.
Related: With the loss of Arecibo’s giant dish, people are more vulnerable to space rock, scientists say
But NEOWISE is also not done with Apophis, Mainzer said. Although the instrument shifted to other work after the ‘discovery’, the asteroid will be back in the NEOWISE field of view once it gets close. “We are almost certain to track it down again in April,” she said.
This will again be a valuable scientific opportunity. “When we see it in December, we look at it from one direction; if we get it in April, we’ll probably see it from another direction, right?” Mainzer said. By seeing Apophis several times in different angles, scientists can get a glimpse of the surface of the space rock.
“We can combine the information to hopefully extract some details. I hope we can get some details about the surface roughness, the thickness of any rocks and dust on the surface of the object,” Mainzer said. “It can help us learn a little more about it when we’re very happy.”
Email Meghan Bartels at [email protected] or follow her on Twitter @meghanbartels. Follow us on Twitter @Spacedotcom and on Facebook.