In September 2011, I was honored to be on the speaker roster for TEDxBoulder, which is a local though independently-run version of the much-lauded TED talks. My talk was about saving the Earth from asteroid impacts, something I’ve spent a lot of time thinking and writing about.
The "We have a space program" line is from science fiction author Larry Niven, so I can’t take credit for it, though I modified it to add the "we can vote" bit. Also, this was the biggest audience I’ve ever spoken to, and it was a great crowd. I was almost last on the roster, but the audience was attentive and clearly enjoying themselves. It was a really fun, energizing, and mind-expanding evening.
The other talks that night are being put online as well. If you ever get a chance to attend a local TEDx conference, you should.
One of the enduring mysteries of our solar system is why Uranus is tilted over on its side. If you measure the angle of a planet’s rotation axis (the location of its north pole) compared to the plane of its orbit, you find that all the planets in the solar system are tipped. Jupiter is only 3°, but Earth is at a healthy 23° angle; Mars is too. Venus is tipped so far over it’s essentially upside-down (we know this because it spins the wrong way).
Uranus, weirdly, is at 98°, like it’s rolling around the outer solar system on its side. The best guess is that it got hit hard by something planet-sized long ago, knocking it over (though there are other, more speculative, ideas). The problem with that is that its moons and rings all orbit around its equator, meaning their orbital planes are tipped as well. It’s hard to see how that might have happened, even if you assume the moons formed in that collision (as, apparently, our Moon formed in an ancient grazing impact with Earth by a Mars-sized body).
Well, a team of astronomers have come up with a new idea: maybe Uranus wasn’t hit by one big object. Maybe it was hit by two smaller ones.
The MESSENGER spacecraft, orbiting Mercury for nearly a year now, took this pretty nifty shot of the tiniest planet’s south polar region, showing deep, dark craters in the Goethe basin:
This region is about 300 km (180 miles) from the true south pole of the planet. On Earth that might be a cold spot, but on Mercury, cold spots are hard to come by.
… however, see how dark those craters are? Since they’re near the pole, the Sun never gets far above the horizon for them, and the crater floors are shrouded in perpetual darkness. That does make them cold! Well below the freezing point of water, it’s thought. Interestingly, radar observations of Mercury have indicated something in the crater floors is highly reflective, and water ice fits that bill. It’s not at all confirmed, but it’s entirely possible Mercury — a planet hot enough in the open Sun where zinc can exist as liquid lakes on the surface — might have frozen lakes of ice locked in crater bottoms near its poles!
While gazing idly at this picture, another thought popped into my head. (more…)
[Update: It looks like the cause of this was a gas bottle exploding, and not a meteorite. See the update for 21:15 UT below).]
A deadly explosion and fire occurred in Argentina overnight, reportedly killing one woman and injuring several others. Two homes, a store, and several vehicles were destroyed or damaged.
The thing is, while it’s not clear what caused this incident, several people said they saw a ball of fire descend from the sky when it happened.
Neighbors’ accounts describe a ball of fire coming from the sky as the cause of the explosion. The chief of the firefighters, Guillermo Pérez, however, said the "causes remain unknown" and that "gas containers were found intact," ruling out a gas related incident.
Other reports are similar; in that article the ball of fire was described as being blue. I know a lot of folks will think this was caused by a meteor, but it’s a bit early to run with that yet. For one thing, it could’ve been a small plane on fire, for example; this happened very early in the morning (2:00 a.m.), and from the reports I’m seeing it’s not clear if the witnesses were already awake when they saw this or were awakened by it. Eye witness reports are notoriously unreliable, and it can’t help if the witnesses were suddenly woken up.
[Update (17:30 UT): This is looking less like a meteorite to me; this news story has a witness saying he saw the blue fire after hearing the explosion, and after he went outside to see what was what. Thanks to JoseManuelp2 for the link.]
As testament to that, I’m seeing some reports that the ball was red, and a picture was posted to the imaging site yfrog claiming, without any any supporting evidence, to be a shot of it. I include it here; note it’s very dark, out of focus, and very low resolution (from the pixelation). I have no clue what this picture shows, but I have my doubts it’s a fireball. I expect we’ll be seeing lots of rumors and things like this today.
[Update (21:15 UT): The image shown here of the red fireball is a hoax, and the man responsible for it has been arrested. Also reported in that link is that there were gas bottles secretly hooked up to a pizza making stove in a nearby house, and that this may be the cause of the explosion. I expect that is the final straw on this story -- enough evidence is piling up that this was not something form space, or even from the sky; it was some kind of terrestrial event, as expected.]
The explosions and devastation appear to be very real, though. This is the only video I could find on YouTube, and it has no audio, but it shows the aftermath:
I don’t see any obvious airplane wreckage, but it’s hard for me to see that a meteorite impact would’ve done this; for it to have been big enough to cause this much devastation, there would’ve been a big crater as well (like the one that hit in Peru a couple of years back). None is evident, so I’m strongly of the opinion something more terrestrial was to blame here.
I won’t be surprised to hear people asking if this was from the UARS satellite, too. However, that’s pretty much impossible; the satellite came down Friday night, and there couldn’t have been pieces of it still in orbit two days later. Also, again, the type of destruction seen here is unlikely to have been from just a simple impact.
Hopefully we’ll find out soon. If you hear anything please leave a comment below (with a link if you have one), and I’ll post an update when I learn more.
[Update: A grass fire in Texas Saturday night has been reported, and it's claimed to be linked to something falling from the sky. Again, a meteorite is extremely unlikely there, since it would take a big impact to ignite fires. Stuff like this happens all the time, and remember Texas is extremely dry right now. I would guess this was fireworks, but there's not much info on this story either. Thanks to Baron Grim on Twitter for the story.]
Tip o’ the Whipple Shield to Antropomorficah on Twitter. Image credit: screen grab from embedded C5N video.
I’ve been scratching my head for a long time, trying to figure out why NASA hasn’t been taking the idea of preventing asteroid impacts more seriously. This idea has everything you’d want in a project: it’s cool (I mean, c’mon, we’re talking asteroid impacts!), it’s doable, it’s not terribly expensive, it’s already on the public’s mind thanks to Hollywood, and there’s always the eensy-weensy possibility that you might save all of humanity.
Yet, despite this, it’s been an uphill battle to get NASA to pay attention. While the space agency has been very good about supporting early detection programs, the support for a space mission to prevent an impact has been lacking. Of course, given their relatively small budget (<1% of the federal spending) I imagine taking on anything like this would be difficult.
So I’m pretty chuffed that the European Space Agency is looking into saving our collective skins. They’ve being studying the feasibility of a mission to test methods of asteroid impact mitigation, including a very very cool space mission they’ve dubbed Don Quijote (first proposed in 2002, and may launch sometime after 2020). It’s actually two separate spacecraft: one to impact a small near-Earth asteroid, and another to monitor the event carefully to see what happens, including how much the orbit of the asteroid was changed.
The idea here isn’t complicated: if we see an asteroid on an impact trajectory with Earth, we want to change the orbit so it doesn’t hit us. We could try blowing it up, but that’s actually a bad idea: at best it creates a lot of debris that can still smack into us, some of which may still be big enough to do us serious harm. So a better idea is to make sure it doesn’t hit us at all.
A giant impact from an asteroid or comet can ruin your whole day. Or year. Or, if you’re a dinosaur, your existence.
So astronomers do what they can to understand this menace from space. We look for rocks on orbits that intersect ours, we think about ways of moving them out of the way should we find one, and we also think about the record we do have of past impacts to see what we can learn from them.
There are about 180 impact craters known on our planet, ranging from tens of millennia in age to billions of years. They also vary in size from a few kilometers across to monsters so big they can only be detected from space. Sometimes it’s hard to measure their size (they can have multiple concentric rings, or be underground — covered up due to extreme age — making definite sizes hard to figure out) or hard to get their age. But we do have some statistics on them, and there have been many studies about them.
A big question is: are impacts periodic? That is, do they happen with some repeating period? If so, then there must be some astrophysical cause: a giant planet in the outer solar system, for example, that shakes loose comets every 50 million years, or the Sun passing near another star. This has been studied, and all kinds of periods have been found in the data. I’ve always been a little skeptical of them, since the data are sparse. And now it looks like my thoughts are being supported: a new study finds no such pattern in the ages of craters, and concludes all the periods found previously are probably due to errors in the analyses.
NASA’s Dawn mission team just revealed the first full-frame image of the giant main-belt asteroid Vesta, and it’s really, really cool:
Yegads! [Click to asteroidenate.]
Vesta is about 500 km (300 miles) across, but is clearly non-spherical, so take that as an average. That’s roughly the size of Colorado! So it’s a big rock, and we’re now seeing it in exquisite detail. This image was taken on July 24, from a distance of about 5000 km (3000 miles).
Man, there’s nothing like being there.
There’s a lot to see. The surface of Vesta is varied, with craters of various sizes (as expected) and depths. I’m very curious to see that there are some darker spots (like in this image) that look like material dredged up from under the surface from impacts; we see this on the Moon and other bodies as well. Some preliminary mineralogical maps show varied distributions of minerals on the surface as well.
An animation of Vesta rotating has also been put together, and really shows how odd this little world is:
[Make sure to set the resolution to at least 720p!]
Look at how the surface changes: you can see smoother regions, cratered regions, places that are darker, some where it’s brighter. Clearly Vesta has been battered over time — the entire south pole region is an impact basin, and those parallel grooves are from waves of energy moving through the asteroid during the impact event — and hopefully its history will be unraveled when higher-resolution images come in.
In fact, the scientists at the press conference talked at length about how these first images have raised a lot of questions, and stressed several times how more images will reveal the answers. Dawn will orbit Vesta for a full (Earth) year, so we should get plenty of data that will keep folks busy for a long time.
… and it won’t end there. After Dawn leaves Vesta it’ll head over the Ceres, the largest of the main belt asteroids. I wonder what it’ll find there? But it’s too soon to worry about that! We have a whole new world to explore for now.
Phil Plait, the creator of Bad Astronomy, is an astronomer, lecturer, and author. After ten years working on Hubble Space Telescope and six more working on astronomy education, he struck out on his own as a writer. He's written two books, dozens of magazine articles, and 12 bazillion blog articles. He is a skeptic and fights the abuse of science, but his true love is praising the wonders of real science.
The original BA site (with the Moon Hoax debunking, movie reviews, and all that) can be found here.
Contact me: The Bad Astronomer "at" gmail "dot" com
"If things worked the way I wanted them to, any reporter about to do another 'sensational' story on deadly meteors would consult this volume, and bang! common sense would find its way into the news. How strange would that world be?" -- Adam Savage, Mythbusters
"Reading this book is like getting punched in the face by Carl Sagan. Frightening, but oddly exhilarating." -- Daniel H. Wilson, author of How to Survive a Robot Uprising
In September 2011, I was honored to be on the speaker roster for TEDxBoulder, which is a local though independently-run version of the much-lauded TED talks. My talk was about saving the Earth from asteroid impacts, something I’ve spent a lot of time thinking and writing about. 
