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.

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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.

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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.

Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

A pair of astronomers monitoring an all-sky camera got a surprise (PDF) when they checked data from last February: a half dozen meteors all seemed to come from the same spot in the sky, indicating they all had a common origin. After doing some calculations, they found that they probably come from a parent comet with an orbit that’s at least 53 years long. Moreover, the orbit of this comet crosses that of the Earth, meaning we may have a close encounter with this object sometime in the future.

And because I can sense the oncoming panic on the web over this news, let me break it down for you. I’ll give you the science (which is cool), how we know this unseen comet may be potentially, um, interesting, then the reason you don’t need to run around in circles screaming (spoiler: it’s rude to others nearby, but also unnecessary).

But just to be up front: should you panic? Nope. We know there are objects out there that could hit us in the future sometime. This comet is in many ways just another one. As I’ll point out below, we pass through lots of meteor streams, so there are plenty of other comets that could hit us. I know, I know, that doesn’t sound reassuring, but think about it: how often is the Earth hit by a comet? Not very often, despite having a few on the list of Potentially Hazardous Objects. So having one more we know about out there isn’t great, but in reality doesn’t really make things any worse for us.

Meatier showers

That picture above is one of the meteors in question. You can see the streak as the tiny bit of rock (probably the size of a grain of sand) glowing as it rammed through the Earth’s atmosphere at about 35 km/sec (22 miles/sec, or nearly 80,000 mph). If you go out on any dark night, you’re bound to see the random meteor or five. But meteor showers are when we see lots of them in a short time, and they occur when the Earth passes through the dust debris left behind by a comet.

Most comets are dirty snowballs: dust, pebbles, and boulders held together by ice (water ice, but also frozen carbon dioxide and other things we normally think of as gases). This makes comets the litter bugs of the solar system, shedding material when the Sun warms them up and turns the ice into gas. The vapor blows off, and the looser material forms a ribbon or stream that stays more or less along the same orbit as the comet.

If the path of the comet intersects the orbit of the Earth, we plow through that material at the same time every year. (more…)

As I write this, in less than a half hour (at 19:40 UT) an asteroid 1-2 meters in size will pass about 12,000 5500 km from the Earth’s surface: less than 7500 3500 miles! The Earth itself is 13,000 km across, so this is a close shave indeed. [UPDATE: Turns out the miss distance of 12,000 km was measured from the Earth's center. Subtracting our radius of about 6400 km, the rock actually came about 5500 km from our surface -- so, even closer than I originally thought. Sorry about the error, and thanks to Emily at The Planetary Society Blog where I saw the actual number.]

Still, it will miss, and would not be dangerous even if it did hit us. Got that? Cool.

This rock, officially named 2011 CQ1, was discovered just last night! Here’s a shot of it taken using a small 0.35 meter (14″) telescope at the Tzec Maun Observatory in New Mexico:

This is a combination of 20 short exposures tracking the asteroid; the stars appear as dotted lines while the asteroid itself as the indicated dot.

Now let me be clear: this rock will miss us, and even if it had been aimed at us it would be unlikely in the extreme to do any damage. It’s way too small. Most likely were something like this to hit us, it would explode very high in the Earth’s atmosphere, releasing as much energy as perhaps a ton or so of TNT. That may sound like a lot, but it’s actually not a big deal. Some estimates have us getting hit by meter-size rocks once per month or so. The fact that you never hear about them indicates they are no danger!

It would take something far bigger to hurt us. The rock that blew up over Tunguska in 1908 was probably 30 meters or so in size; that detonated with a yield of about 15 – 20 megatons of TNT, equivalent to a pretty big nuke (though without radiation). Something metallic that size would probably hit the ground intact, leaving a hole like Arizona’s Meteor Crater, which is over a kilometer across. Happily, impacts like that are extremely rare!

Smaller ones are more common. In late 2008, a smallish rock about the same size as 2011 CQ1 came in over the Sudan and exploded, raining down small rocks which were later recovered. No one was hurt.

So the point here is that CQ1 is too small to hurt us even if it were to hit, which it won’t. And the cool thing is that it was seen at all! Two meters is dinky indeed, and this kind of discovery, far from being scary, makes me happy because it means we’re getting better all the time at detecting rocks that might actually hit and do damage.

Image credit: Giovanni Sostero & Ernesto Guido. Tip o’ the Whipple Shield to reddit.

As recently promised, the European Space Agency’s Mars Express probe made a very close pass of the small moon Phobos, taking incredibly detailed pictures of the spud-shaped rock. Emily Lakdawalla, as always with planetary missions, has the what-fors with this event.

When it was a mere 111 km (66 miles) from the moon, Mars Express took this amazing image:

Click it for the full-res version is a whopping 7800 x 5200 pixel, 13 Mb TIF barsoomenated version. The detail is incredible, with features as small as 8 meters (roughly 25 feet across). Since Phobos is about 27 km (17 miles) long, that’s a lot of detail!

But as regular readers know, I have a thing for 3D red/green anaglyphs, and as the probe passed the moon naturally took stereoscopic images. The folks at ESA put two together to make this jaw-dropping 3D shot of Phobos:

Click it to get 3800 x 2600 pixel, 13 Mb TIF version. You really want to. If you have red/green glasses, this is one of the best anaglyphs from space you’ll see. I’ve never seen something stick out of my screen like this! Also, the details were so sharp that if I shake my head back and forth (like gesturing "no") I can actually see Phobos rotate a little bit, due to the change of positions of my eyes! That was new to me as well, and is very cool. it really solidifies the illusion that you’re seeing an object three-dimensionally.

Mars is an astonishing place, and it’s easy to forget how interesting its two moons are (the other is Deimos, which is smaller than Phobos). Their origins are still something of a mystery, and the surface features on Phobos are not totally understood either. (more…)

The sky is big. Searching it for potentially hazard objects like asteroids and comets is hard. The best way to do it? A big ‘scope, equipped with a BIG camera, and a wide, wide field of view. That’s just what the Panoramic Survey Telescope & Rapid Response System — PanSTARRS — brings to the table. It’s just a prototype, but it has a 1.8 meter ‘scope on — wait for it, wait for it — Mount Haleakala, and it sports a 1.4 gigapixel camera. You read that right: 1.4 billion pixels.

It scans the skies looking for threatening objects, and astronomers just announced they have found their first one: 2010 ST3, an asteroid 50 meters (150 feet or so) across. It was found September 16, when it was still 30+ million kilometers (20 million miles) from Earth. Here’s the object in question:

How big a threat is this object? Well, not very: there’s "a very slight chance" it will hit Earth in 2098, so I’m not terribly concerned. When astronomers map an orbit of an object, there’s some uncertainty in the measurements. It’s hard to get the exact position of the object, and its motion over a day or two isn’t enough to get a good idea of its trajectory. The farther you try to project where it’ll be in the future, the fuzzier the prediction gets.

For something like 2010 ST3, there’s a huge volume of potential space it might occupy come 2098, and it so happens that the Earth is in that same volume of space at that time. But the Earth is near the edge of the projected position, and as time goes on, and the orbit is better determined, the volume of space the asteroid might be in will shrink. Eventually, what almost always happens is that the Earth winds up outside that volume as our data get better. That’s why the odds of it hitting us are so low.

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