News services dialed their headlines back a bit Tuesday. But Monday’s planetary defense test was a big deal, no matter how much of a nudge it gave Dimorphos.
NASA successfully redirects asteroidNASA successfully crashes into asteroid“
Natasha Zouves, Devan Markham, Kelsey Kernstine; (NewsNation)/KTLA 5 News (
September 26, 2022September 27, 2022)
“NASA successfully completed its Double Asteroid Redirection Test (DART) on Monday, launching a spacecraft into an asteroid.
“The goal: To change the path of the asteroid, diverting it away from Earth.
“Don’t fret. There was no real threat here on Earth.
“The collision happened 7 million miles away from our planet, and the technology could someday be used to save humanity in an ‘Armageddon’ situation, according to NASA….”
Maybe my news feed isn’t inclusive enough. Or maybe “tampering with things man was not supposed to know” lost its popular panache, somewhere between the decline of disco and the rise of rave. More to the point, history happened on Monday, September 26, 2022.1
“NASA’s DART Mission Hits Asteroid in First-Ever Planetary Defense Test“
Josh Handal, NASA; Justyna Surowiec / Michael Buckley, Johns Hopkins Applied Physics Laboratory; Press release (September 26, 2022; Updated September 27, 2022)
“After 10 months flying in space, NASA’s Double Asteroid Redirection Test (DART) – the world’s first planetary defense technology demonstration – successfully impacted its asteroid target on Monday, the agency’s first attempt to move an asteroid in space.
“Mission control at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, announced the successful impact at 7:14 p.m. EDT.
“As a part of NASA’s overall planetary defense strategy, DART’s impact with the asteroid Dimorphos demonstrates a viable mitigation technique for protecting the planet from an Earth-bound asteroid or comet, if one were discovered.
“‘At its core, DART represents an unprecedented success for planetary defense, but it is also a mission of unity with a real benefit for all humanity,’ said NASA Administrator Bill Nelson. ‘As NASA studies the cosmos and our home planet, we’re also working to protect that home, and this international collaboration turned science fiction into science fact, demonstrating one way to protect Earth.’…”
By any reasonable standard, this is a big deal. Although I still cringe when I read “unprecedented” in a press release. And that’s another topic.
How much of a big deal? That’s something we’ll learn over the next several months.
Crashing into an astronomical body isn’t new.
Images sent back by DART’s camera as it flew into Dimorphos reminded me of the 1960s Ranger program: when, finally, Ranger 7 got off the pad, hit the moon and sent back pictures.
Hitting our 2,000-mile-wide moon with a five-foot-wide by 12-foot-tall spacecraft wasn’t going to change the moon’s orbit.
But this time, since Dimorphos is only a little over 500 feet across, and DART was moving very fast, scientists figure they’ve changed its orbit around Didymos.
Granted, DART only weighed 1,340 pounds, 610 kilograms — it’s a little larger than a vending machine — so it won’t have affected the orbit by much.
But astronomers have been keeping close track of the Didymos-Dimorphos pair for months. They’re reasonably sure they’ll get good numbers for how much the orbit has changed.
Dimorphos orbits Didymos about once every 12 hours. Astronomers will want observed times for many orbits, since the change may be barely measurable. We almost certainly won’t get results for a few months. They’ll want lots of timed orbits.2
And here’s a NASA news conference video, starting at 31:00/32:05, when they showed DART’s approach with a time lapse compiled from the probe’s camera.
(“NASA’s DART Mission Post-Asteroid-Impact News Briefing,” NASA (Sept. 26, 2022)
If editors editors had felt the urge, we might have seen far more colorful coverage.
Think “The Green Slime” meets “When Worlds Collide,” with a dash of “The Andromeda Strain.”
But, again, I haven’t seen scary ‘asteroid of doom’ headlines. I see this as good news.
On the other hand, Didymos-Dimorphos is a PHO, a potentially hazardous object and a NEO, near-Earth object. So I’m a little surprised that nobody’s sounding the alarm over NASA’s plot to destroy us all.
Not that I’ve noticed, that is; and I said surprised, not disappointed.
At any rate, Didymos-Dimprphos is a PHO because the asteroid pair’s orbit brings it almost as close to the sun as Earth: 1.0131 astronomical units.
Running a vending-machine-size robot into the pint-size portion of the pair won’t send it hurtling toward Earth.
But given time, gravitational interaction with the other 10,484 known Apollo asteroids might change the pair’s orbit so that they cross Earth’s orbit when Earth’s in that spot.
Then there are the ten thousand or so other Near-Earth objects we’ve spotted, plus everything else in the Solar System. Even if Didymos-Dimprphos never hits Earth, something else will.
Either Didymos, or Dimorphos, or both, falling out of our sky could be unpleasant. That’s why NASA, ESA and others have been planning missions like DART. I’ll get back to that.
When NASA and JPL went looking for DART target, their choices narrowed down to one.
The target had to get close enough to Earth, so that astronomers can measure its orbital period before and after impact. And still be far enough away so that the pair’s no more a threat than any other Apollo asteroid.3
Again, Dimorphos is a little over 500 feet across. Didymos is considerably larger: 2,625 feet, roughly a quarter-mile across.
Dimorphos is almost certainly a ‘rubble pile’ — bits and pieces of rock held together (loosely) by the pile’s (slight) gravity.
Didymos may be a rubble pile, too, which might account for its equatorial ridge. Then again, maybe it isn’t. I haven’t found anything definite on the point.
Now, let’s compare that pair to an asteroid that did run into Earth.
The object that lit up the sky over Chelyabinsk back in 2013 was about 56 feet across.
The Chelyabinsk meteor was smaller than either Didymos or Dimorphos, on a different orbit, and probably made of different stuff. So comparing the two would be an apples-to-oranges situation.
On the other hand, either Didymos or Dimorphos are a great deal bigger than thing that detonated over Chelyabinsk.
Happily, folks recognized the Chelyabinsk air burst as a natural phenomenon almost from the get-go, nobody got killed, and cleanup wasn’t much worse than major storm damage.
And the folks running Russia weren’t “demilitarizing” one of their neighbors in a “special military operation.” back in 2013.
Ideally, even if something brighter than the sun exploded over either Moscow or Kyev today, whoever’s in charge would verify that it wasn’t a nuclear bomb before launching a counter-strike. But as I keep saying, we don’t live in an ideal world.4
Something like the Chelyabinsk event happens every few years, on average, somewhere on Earth. Only a few are newsworthy, since something like three quarters of the planet is ocean, and cities only cover a bit of the land.
That’s a good thing, since the blast was a thousand times more powerful than the one that punched out walls in Chelyabinsk.
I’ve given intervals between impacts as averages. Once every millennium could mean, for example, two ‘Tunguska events’ a year apart, than two millennia of just little booms.
So far, we’ve been lucky.
Apart from maybe the 1490 Ch’ing-yang event — which I gather some scholars say wasn’t properly documented — we don’t have records of a Tunguska-level event happening over a densely-populated area.
But I’m not sure that’s a comforting thought. We know about the Ch’ing-yang event because it happened in a province of China, about halfway through the Ming dynasty. The disaster affected only one part of a well-organized empire.
But for quite a bit of humanity’s history, a prosperous city-state might have been abruptly depopulated without leaving detailed records of the event.
Record-keeping, after all, requires observers and some way to record information from the observers. Today, observers could be near ground zero — and still preserve significant data before they died.
Like Robert Landsburg, who was near Mount Saint Helens when it went up.
As a pyroclastic cloud approached him, he took photos, rewound the film, put the camera in a backpack and shielded the backpack with his body. When searchers found his body, 17 days later, the film was intact.5
(“Eyes on Asteroids“, “Real time visualization of every known asteroid or comet that is classified as a Near Earth Object (NEO).” (NASA/JPL))
Nobody had been tracking the Chelyabinsk object when it entered Earth’s atmosphere, partly because it came in from the general direction of the sun.
We’ve been finding and tracking a great many asteroids and comets since 2013, but I figure we haven’t spotted them all.
Even if astronomers did spot something like 99942 Apophis — an asteroid that’ll come close to Earth in April of 2029, but will miss us — heading for an impact in, say, 2032: we don’t have technology in place that could prevent it.
The good news is that the DART mission has been a success so far, and we’ll have at least preliminary data on its effectiveness in a few months.
Maybe, by some miracle, members of the United States Congress could be convinced that the incoming asteroid wasn’t a plot by the other party: and give NASA the okay to save their lives.
We’re not the only fish in this pond, of course. Maybe the Parliament of Singapore would get the ball rolling.
In any case, I’m pretty sure that cobbling together an effective asteroid mover would involve NASA, ESA, JAXA and anyone else with tech and talent who’s living on Earth.
As it is, JAXA, the Italian Space Agency and several private aerospace companies have been involved in the DART mission.6
By the way, I recommend the NASA/JPL “Eyes on Asteroids” interactive visualization of stuff in the inner Solar System. It’s regularly updated, with fairly intuitive rotate-and-zoom controls: so it may take a while to load. But again: I recommend it.
Right now, we’ve got a whole mess of methods for moving asteroids so that they won’t hit Earth; but we don’t know which look good on paper and will actually work.
That’s one of the reasons for the DART mission. In geek-speak, it’s a test of the kinetic impact method: basically, using Newton’s laws of motion the way we do while playing billiards. Which is a subset of cue sports, and that’s yet another topic.
Kinetic impact asteroid deflection is something we can do right now.
It’s something we have done, as of Monday, September 26, 2022.
What we don’t know yet is how much of the DART probe’s momentum transferred to the rubble pile we call Dimorphos. There’s also the question of what’s happened to Dimorphos, apart from a slight change in velocity.
Another, Hollywood-friendly, asteroid deflection method is setting off a nuclear bomb on or in the thing.7 Practical issues aside, I’m guessing this alternative will have to wait until politicos and activists are a trifle less rabid when atom bombs are in play.
Skipping over esoteric tech like ion beams, laser ablation and gravity tractors — that last isn’t, or isn’t quite, science fiction’s “tractor beam” and might be practical, someday — I think Deep Space Industries was on the right track, with their proposed asteroid mining systems.
On the right track, but decades to maybe a century ahead of the curve. Bradford Space acquired Deep Space Industries in 2019. Bradford Space has been focusing on logistics and components that folks need now.8
The good news is that NASA, ESA and a great many other organizations and individuals have been cooperating; tracking objects that might hit Earth, and working the bugs out of tech that can keep us from learning what a Tunguska event looks like when a city’s under the blast.
This is a good time for that sort of research and development: before we spot an asteroid headed our way.
ISA’s LICIACube CubeSat, a miniature spacecraft that had been riding with the DART mission, sent back that image a few minutes after DART hit Dimporphos.
Scientists will be analyzing, comparing, debating and learning from images like that and other data: for years, most likely. As I said earlier, we’re learning.
I think we will have the tech needed to keep rocks like the one that detonated over Chelyabinsk from hurting folks: before something like that happens over another city. Probably.
Again, although we’re getting a handle on how often on average impacts of a given size happen: that doesn’t tell us when mountains will fall out of the sky.
The odds are better that we’ll be ready in time to prevent another Tunguska event.
And we have, probably, quite a long time before something the size of the Canyon Diablo meteorite blows a kilometer-wide hole somewhere on our home.9
But, and maybe this is a no-brainer, but: is it right to try keeping folks from being killed?
Now, since I’ve noticed no recent religious objections to weather forecasts or lightning rods, I’m guessing that most folks have gotten over the notion that we should let disasters happen.
“…’It’s scary. It’s this new language that’s forming — I don’t even recognize,’ she said. ‘It’s scary to know, it’s been proven through science, that climate change is due to human activity. And we continue to ignore it, and the only voice we have is through voting,’ Lawrence said. After Long said the American public had recently voted and selected Trump, who has denied the existence of climate change in the past, Lawrence said the result was “startling.’
”’You’re watching these hurricanes now, and it’s hard — especially while promoting this movie, not to feel Mother Nature’s rage and wrath,’ she said….”
(“Jennifer Lawrence calls hurricanes ‘Mother Nature’s rage and wrath’,” Entertainment Weekly (September 8, 2017))
“… There was the burgeoning Gulf Coast gambling industry, with a new casino that was to open on Labor Day weekend. But of course, what is a little gambling if it supports ‘education’ and brings revenue into government coffers? And then there was the 34th Annual gay, lesbian and transgender ‘Southern Decadence’ Labor Day gala to be held from August 31st to September 5th….”
(“Katrina: God’s Judgment on America” Anonymous; Restore America, via Beliefnet (2005))
“I have read in the Philosophical Transactions the account of the effects of lightning on St. Bride’s steeple. ‘Tis amazing to me, that after the full demonstration you had given, of the identity of lightning and of electricity, and the power of metalline conductors, they should ever think of repairing that steeple without such conductors. How astonishing is the force of prejudice even in an age of so much knowledge and free enquiry!”
(Letter, To Benjamin Franklin from John Winthrop, 6 January 1768, via founders.archives.gov)
Religious scruples regarding “metalline conductors” — lightning rods — is something that’s taken on a life of its own over the last two and a half centuries, and that’s yet again another topic, for another day.
I don’t see a problem with using our brains or saving lives, partly because I’m a Catholic.
And since I’m a Catholic, I realize that our dominion doesn’t mean we can do whatever we like with our home.
Our “dominion” means having the authority and responsibility that comes with one of our jobs: taking care of this world and leaving it in good condition for future generations. (Catechism of the Catholic Church, 16, 339, 356-358, 2402, 2415-2418, 2456)
And I figure that includes keeping an eye out for falling mountains, and developing the tech needed to nudge them aside when necessary.
I was going to talk about DART’s autonomous navigation system, ESA’s follow-up mission, and what we’ll be learning about asteroids. But I’ve run out of time this week.
Meanwhile, here’s vaguely-related stuff:
- “Green Sahara, Environmental and Climate News“
(July 30, 2022)
- “A Winter Weather Advisory, Forecasts and Making Sense“
(January 13, 2021)
- “My Top 10 Science News Stories For 2020“
(December 29, 2020)
- “Space ‘Firsts:’ New Horizons, Chang’e-4“
(January 18, 2019)
- “Near-Earth Asteroids“
(November 4, 2016)
- The Johns Hopkins University Applied Physics Laboratory LLC
- 65803 Didymos
- Double Asteroid Redirection Test (DART) Mission
- “NASA’s DART Mission Post-Asteroid-Impact News Briefing,” YouTube video (32:05) (September 26, 2022)
- The Orbit of Didymos (JPL) (November 17, 2021)
- CNEOS: Center for Near Earth Object Studies (JPL)
- “NASA’s DART Mission Post-Asteroid-Impact News Briefing,” YouTube video (32:05) (September 26, 2022)
- Planetary Defense
- Part of my take on the mess in Ukraine
- “Ukraine, Russia, Annexation; and Learning from History” (April 30, 2022)
- “Ukraine: Invasion, Annexation, Labels, and a Good Idea” (March 19, 2022)
- “[meteorite-list] Meteorite deaths in Qingyang (Ch’ing-yang) in 1490“
Sterling K. Webb, email (January 1, 2010) via mail-archive.com
- “Orbital Elements of Comet C/1490 Y1 and the Quadrantid shower“
Ki-Won Lee, Hong-Jin Yang, Myeong-Gu Park; Earth and Planetary Astrophysics, Astrophysics; arXiv, Cornell University (submitted on August 18, 2009)