Planetary Defense
Meteor in Russia (February 2013): Why weren't we warned about the meteor that struck in Russia?
Robert Frost, engineer/instructor at NASA
The latest reports indicate the meteor entered the atmosphere at a relative speed of about 33,000 mph. That means it was moving in the opposite direction of Earth and we hit it head on. At that speed, just seven hours earlier it would have been as far away as the moon. It was the size of a bus. Even the Hubble telescope couldn't see a bus parked on the moon.
Too small. Too fast. Too dark.
It also entered the atmosphere over a desolate part of Siberia that likely does not have good radar coverage. And it entered from the daylight side, which means it would not have been visible to telescopes.
Alex Whittemore, Engineer with a rocket problem.
Robert Frost's answer is obviously spot on. The real reason is just that - too small, too fast, too dark. But let's focus on small - he says the Hubble couldn't see a bus parked on the moon.
The meteor was about 15m across (roughly bus-sized). The average distance between the Hubble and the moon (which obviously isn't the closest it gets, but it gives you an idea of the problem) is 377441km, or thereabouts. Thus, tan^-1(15m/377441km) = 2x10^-6 degrees is the angle the meteor(bus) on the moon would occupy in Hubble's field of view. Its resolution is .1 arcseconds (if you don't get the concept of optical resolution, I don't blame you, but google it. It's certainly interesting), or 2.8x10^-5 degrees. Thus, a bus on the moon (the meteor) is 10x too small for Hubble to even make out that something is there.
There have also been a number of cynical answers suggesting that the underlying reason for not knowing about it was that we simply aren't looking. That's true. The optical math above only serves as an example for how difficult the problem of 'seeing' something this size is. But optical isn't what you'd use for asteroid detection. The REAL question is, why BOTHER looking?
From a life-saving perspective, ~1000 people were injured (mostly by broken glass) with no recorded fatalities. An object of this size falls to earth on the order of once in 100 years. Given the low loss of life, you'd almost certainly be better off spending the millions or billions of dollars on a public health campaign/cancer research/water supply cleanliness than on an early detection system sensitive to these kinds of objects.
From a cost perspective, Russia estimates that the damage from this event could be as high as $33m USD. If you could run a meteor detection program with only a SINGLE satellite (and that would be a huge, huge stretch), you're looking at around $50m USD to get it to low earth orbit, BEST case, on a Falcon 9, which is the cheapest commercial launch vehicle there is. EVEN if you could construct a satellite to last 100 years (you can't), you're talking about wasting ~$17m every hundred years on launch cost alone, much less development and hardware. It just doesn't make sense to bother.
Bottom line, was this meteor strike scary? Yes. Dangerous? No, not really.
Sources:
hubble resolution: http://www.spacetelescope.org/about/faq/
Tom Byron, I was once snowed in for 5 days.
Not possible to see a "gnat or a fly" at 50 miles. The analogy may be exaggerated but the concept is not. When an amateur astronomer found the asteroid DA14, it was 150' long. Tiny. (Deleted offensive remark to this being lucky, sorry I offended some by this remark.) The meteoroid that landed in Russia was about 1/3 that size, and traveling at 33000 MPH, black, against a black sky. Good luck spotting that gnat in the dark at 50 miles out.
Then even if they did, they would have about 5 minutes to warn everyone. How? The panic would do more harm, since you can't protect your self from impact. Note, at 33,000 per hour, three hours before impact (time for some to get away) this 50' piece of rock was 100,000 miles away, not easy to see.
No one got killed, so far as we know. (Deleted reference to glass repair work. Sorry I offended some readers.)
[EDIT]
Meteor warning system in the works - but not ready yet
There aren't yet any advance warning systems that could give Earthlings a heads-up before an untracked space rock hits. But a telescope project in Hawaii aims to change that, and potentially provide a chance for those in threatened areas to evacuate. A meteor alert might have made a difference to Russia's Chelyabinsk region on Friday.
Bill Pardue, Librarian, Arlington Heights (IL) Memorial Library
NASA also has a nice blog entry about this: Why Wasn't the Russian Meteor Detected Before it Entered the Atmosphere?
Robert Frost, engineer/instructor at NASA
The latest reports indicate the meteor entered the atmosphere at a relative speed of about 33,000 mph. That means it was moving in the opposite direction of Earth and we hit it head on. At that speed, just seven hours earlier it would have been as far away as the moon. It was the size of a bus. Even the Hubble telescope couldn't see a bus parked on the moon.
Too small. Too fast. Too dark.
It also entered the atmosphere over a desolate part of Siberia that likely does not have good radar coverage. And it entered from the daylight side, which means it would not have been visible to telescopes.
Alex Whittemore, Engineer with a rocket problem.
Robert Frost's answer is obviously spot on. The real reason is just that - too small, too fast, too dark. But let's focus on small - he says the Hubble couldn't see a bus parked on the moon.
The meteor was about 15m across (roughly bus-sized). The average distance between the Hubble and the moon (which obviously isn't the closest it gets, but it gives you an idea of the problem) is 377441km, or thereabouts. Thus, tan^-1(15m/377441km) = 2x10^-6 degrees is the angle the meteor(bus) on the moon would occupy in Hubble's field of view. Its resolution is .1 arcseconds (if you don't get the concept of optical resolution, I don't blame you, but google it. It's certainly interesting), or 2.8x10^-5 degrees. Thus, a bus on the moon (the meteor) is 10x too small for Hubble to even make out that something is there.
There have also been a number of cynical answers suggesting that the underlying reason for not knowing about it was that we simply aren't looking. That's true. The optical math above only serves as an example for how difficult the problem of 'seeing' something this size is. But optical isn't what you'd use for asteroid detection. The REAL question is, why BOTHER looking?
From a life-saving perspective, ~1000 people were injured (mostly by broken glass) with no recorded fatalities. An object of this size falls to earth on the order of once in 100 years. Given the low loss of life, you'd almost certainly be better off spending the millions or billions of dollars on a public health campaign/cancer research/water supply cleanliness than on an early detection system sensitive to these kinds of objects.
From a cost perspective, Russia estimates that the damage from this event could be as high as $33m USD. If you could run a meteor detection program with only a SINGLE satellite (and that would be a huge, huge stretch), you're looking at around $50m USD to get it to low earth orbit, BEST case, on a Falcon 9, which is the cheapest commercial launch vehicle there is. EVEN if you could construct a satellite to last 100 years (you can't), you're talking about wasting ~$17m every hundred years on launch cost alone, much less development and hardware. It just doesn't make sense to bother.
Bottom line, was this meteor strike scary? Yes. Dangerous? No, not really.
Sources:
hubble resolution: http://www.spacetelescope.org/about/faq/
Tom Byron, I was once snowed in for 5 days.
Not possible to see a "gnat or a fly" at 50 miles. The analogy may be exaggerated but the concept is not. When an amateur astronomer found the asteroid DA14, it was 150' long. Tiny. (Deleted offensive remark to this being lucky, sorry I offended some by this remark.) The meteoroid that landed in Russia was about 1/3 that size, and traveling at 33000 MPH, black, against a black sky. Good luck spotting that gnat in the dark at 50 miles out.
Then even if they did, they would have about 5 minutes to warn everyone. How? The panic would do more harm, since you can't protect your self from impact. Note, at 33,000 per hour, three hours before impact (time for some to get away) this 50' piece of rock was 100,000 miles away, not easy to see.
No one got killed, so far as we know. (Deleted reference to glass repair work. Sorry I offended some readers.)
[EDIT]
Meteor warning system in the works - but not ready yet
There aren't yet any advance warning systems that could give Earthlings a heads-up before an untracked space rock hits. But a telescope project in Hawaii aims to change that, and potentially provide a chance for those in threatened areas to evacuate. A meteor alert might have made a difference to Russia's Chelyabinsk region on Friday.
Bill Pardue, Librarian, Arlington Heights (IL) Memorial Library
NASA also has a nice blog entry about this: Why Wasn't the Russian Meteor Detected Before it Entered the Atmosphere?