Explanation: Could humanity deflect an asteroid headed for Earth? Yes. Deadly impacts from large asteroids have happened before in Earth's past, sometimes causing mass extinctions of life. To help protect our Earth from some potential future impacts, NASA tested a new planetary defense mechanism yesterday by crashing the robotic Double Asteroid Redirection Test (DART) spacecraft into Dimorphos, a small asteroid spanning about 170-meters across. As shown in the featured video, the impact was a success. Ideally, if impacted early enough, even the kick from a small spacecraft can deflect a large asteroid enough to miss the Earth. In the video, DART is seen in a time-lapse video first passing larger Didymos, on the left, and then approaching the smaller Dimorphos. Although the video ends abruptly with DART's crash, observations monitoring the changed orbit of Dimorphos -- from spacecraft and telescopes around the world -- have just begun.
I applaud NASA for doing this experiment to actually deflect an asteroid - and they apparently succeeded, too.
At the same time, I'm reminded of what happened back in 2013, when NASA had told us that an asteroid would pass between the Earth and the Moon, really very close to us. However, it would not hit us. So when, on the day of close passage of the asteroid, newsflashes started talking about an extremely bright meteor over Russia, I just assumed that this had something to do with the passing asteroid.
Not so. It was the largest meteor to hit the Earth since Tunguska event back in 1908. Both the Tunguska event and the new meteor event over Chelyabinsk, also in Russia, were caused by large rocky objects exploding in the Earth's atmosphere, creating enormous shock waves.
The Chelyabinsk meteor was a superbolide that entered Earth's atmosphere over the southern Ural region in Russia on 15 February 2013 at about 09:20 YEKT (03:20 UTC). It was caused by an approximately 20 m (66 ft) near-Earth asteroid that entered the atmosphere at a shallow 18.3 ± 0.4 degree angle with a speed relative to Earth of 19.16 ± 0.15 kilometres per second (69,000 km/h or 42,690 mph). The light from the meteor was briefly brighter than the Sun, visible up to 100 km (62 mi) away. It was observed over a wide area of the region and in neighbouring republics. Some eyewitnesses also felt intense heat from the fireball.
The object exploded in a meteor air burst over Chelyabinsk Oblast, at a height of around 29.7 km (18.5 mi; 97,000 ft).[7][8] The explosion generated a bright flash, producing a hot cloud of dust and gas that penetrated to 26.2 km (16.3 mi), and many surviving small fragmentary meteorites. The bulk of the object's energy was absorbed by the atmosphere, creating a large shock wave with a total kinetic energy before atmospheric impact estimated from infrasound and seismic measurements to be equivalent to the blast yield of 400–500 kilotons of TNT (about 1.4–1.8 PJ) range – 26 to 33 times as much energy as that released from the atomic bomb detonated at Hiroshima...
The object approached Earth undetected before its atmospheric entry, in part because its radiant (source direction) was close to the Sun.
...
The earlier-predicted and well-publicized close approach of a larger asteroid on the same day, the roughly 30 m (98 ft) 367943 Duende, occurred about 16 hours later; the very different orbits of the two objects showed they were unrelated to each other.
Here is a video where ABC News talked about the Chelyabinsk event:
Click to play embedded YouTube video.
To me, three things about the Chelyabinsk event stand out. It was the largest meteor to impact the Earth since 1908. It struck us at almost the same time as the world was waiting for a near-Earth asteroid to make its closest approach to the Earth. And it appeared "out of nowhere", completely undetected until it showed up brilliantly in the skies over southern Ural.
My point is this:
Will we detect a dangerous rocky object in time to be able to send up a probe to deflect it?
Ann
P.S. And of course... As I googled the Chelyabinsk meteor, I was struck by the pictures of Russia barely ten years ago, when the country was not at war, and Russian men were not being rounded up on the streets to be forcibly sent to Ukraine to be a part of Vladimir Putin's brutal unprovoked war against another country. You really have to wonder what was worse, the Chelyabinsk meteor or Vladimir Putin - and I think I know the answer to that.
Thanks for another good APOD.
Unsolicited copyeditor's note: "170 meters" takes no hyphen. Only measurements expressed as an adjective should be hyphenated: "DART collided with the 170-meter asteroid yesterday."
Something puzzles me about time-lapse videos. I used to think that time speeds up in time-lapse. Say a year passes by in a couple of minutes in the video. But here in NASA's page under Dimorphos they state that Dart impacted the satellite at a speed of 6.6 kilometers a second. Then they state that the two satellites orbit at a distance of about one kilometer apart. So at a speed of 6.6 kilometers a second it should have taken around 1/6th on a second after Dart passed by Didymos until it collided with the smaller asteroid. (Be kind I am not great at doing Math.) Yet in the video at least 3 more seconds pass by before impact. Wouldn't it be more truthful that time lapse here really means slow motion instead of sped up time?
orin stepanek wrote: ↑Tue Sep 27, 2022 2:41 pm
How large of an asteroid will we be able to nudge away from Earth?
How close can it be before nudging is no longer effective?
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk. — Garrison Keillor
alex_515 wrote: ↑Tue Sep 27, 2022 8:37 am
It's curious there is a spot of light on the lower part of DidymosDimorphos, the one plunged into darkness
Alex
I think it's a peak at night's side catching Sun's light
Dimorphos.jpg
But based on the shadows, the Sun seems to be coming from the upper right, no? And if so, that bright spot on the lower left should be in Dimorphos' shadow. So why is it lit up?
-- "To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."{ʲₒʰₙNYᵈₑᵉₚ}
I think that the bright bar in the deep shadow of Dimorphos might be reflective metal (perhaps iron or nickel) reflecting light from its larger partner 65803 Didymos, since this binary asteroid is xk-type with albedo of 0.15. https://en.wikipedia.org/wiki/65803_Didymos
The bright area at the bottom of Dimorphos looks to me like the edge of a large slab of rock that happens to be perched high enough to protrude up into sunlight.
On another note:
Because the warning we receive may not be early enough, we should also pursue more drastic countermeasures against major impact threats.
The US military has tested Earth-Penetrator "Silo Buster" nuclear warheads that could blast a large chunk away from an approaching asteroid. Newtonian physics would suggest a larger and closer object could be diverted in this way. Drastic? Very! ...but consider the alternative.
Bob R wrote: ↑Tue Sep 27, 2022 5:28 pm
The bright area at the bottom of Dimorphos looks to me like the edge of a large slab of rock that happens to be perched high enough to protrude up into sunlight.
On another note:
Because the warning we receive may not be early enough, we should also pursue more drastic countermeasures against major impact threats.
The US military has tested Earth-Penetrator "Silo Buster" nuclear warheads that could blast a large chunk away from an approaching asteroid. Newtonian physics would suggest a larger and closer object could be diverted in this way. Drastic? Very! ...but consider the alternative.
As you probably already know, the problem with trying to "blast a large chunk of an asteroid away" is that you might end up making the problem much worse: your single impactor problem may just have become a 10 impactor problem. This is due to the extreme uncertainty involved in trying to predict how the asteroid will be broken up (if it is at all). You also risk nudging the asteroid into a more certain collision with earth. But the "may not be early enough" problem is very real, particularly with the 50% of asteroids lost in the glare of the sun that we still know nothing about! So, we better get those space telescopes up there pronto to look for them.
-- "To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."{ʲₒʰₙNYᵈₑᵉₚ}
"Ideally, if impacted early enough, " is the functional question of diverting celestial threats. When coming directly from the sun, "early enough" may be far too late, and mankind may have to "live with" the threat, or expend prodigious amounts of capital in an effort o prevent that which could never be prevented!
De58te wrote: ↑Tue Sep 27, 2022 1:46 pm
Something puzzles me about time-lapse videos. I used to think that time speeds up in time-lapse. Say a year passes by in a couple of minutes in the video. But here in NASA's page under Dimorphos they state that Dart impacted the satellite at a speed of 6.6 kilometers a second. Then they state that the two satellites orbit at a distance of about one kilometer apart. So at a speed of 6.6 kilometers a second it should have taken around 1/6th on a second after Dart passed by Didymos until it collided with the smaller asteroid. (Be kind I am not great at doing Math.) Yet in the video at least 3 more seconds pass by before impact. Wouldn't it be more truthful that time lapse here really means slow motion instead of sped up time?
Steve_Hackett_-_Time_Lapse_(1999).jpg (8.6 KiB) Viewed 5077 times
Yes, according to Wikipedia, I see that the term time-lapse should be reserved for this case, where as you said, the playback is swifter than the image capture process.
It turns out that the images in the video are deceptive. It does give us the feeling that the DART spacecraft is just passing Didymos as the video begins.
DART: Impact on Asteroid Dimorphos
