posted
Oh. Also in either/both cosmos and Pale Blue Dot he has the graph of rate of collisions relative to their size (statistically) (They're from some other guy, but they're interesting...)
Posts: 655 | Registered: May 2005
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posted
I'm so watching this one if it hits. Jupiter was amazing and cool in 1994 when Shoemaker-Levy 9 hit! Mars is so much closer! Oh I hope it won't hurt Spirit and Opportunity, though!
Posts: 6246 | Registered: Aug 2004
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posted
By the way, Mars is about the same size planet as Earth. It's a bit closer to the asteroid belt, but otherwise, very similar to earth in all its characteristics as a target body. This should show that there's quite a good chance of these things hitting us as well, and it only makes good sense for us to begin work on a defense system (while, of course, continuing to survey the sky for possible impacting bodies). Had we begun in 1999, when I first started talking about it, we could be nearly ready by now. As it is, we have no idea when we're going to need it. Let's get going on it right away.
posted
We would get out of the way, if possible. It would be too close at this point to do anything but watch. The danger is that it could destroy a city or a small nation if it were to impact land in a populated area. If it hits in Siberia or the ocean, I don't think there would be much to worry about, except for a tsunami.
The Tunguska event was caused by something about the size of the Mars impactor. I went to Impact Effects to see what the damage would be in water. I don't know how accurate the site is, but if true the impactor would open a crater in the water about a mile wide. There would be some big waves from that.
I am hoping that the morning of January 30 is clear here. Mars just left opposition, so the viewing should be great for the Americas.
Posts: 684 | Registered: Jun 2002
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posted
I think they're over-reacting about the devastation of an asteroid. Besides, we've got Chuck Norris.
Posts: 1314 | Registered: Jan 2006
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posted
This should be kept in mind by those who would seek comfort in regarding the Tunguska event as something rare:
quote:The late Eugene Shoemaker of the U.S. Geological Survey came up with an estimate of the rate of Earth impacts, and suggested that an event about the size of the nuclear weapon that destroyed Hiroshima occurs about once a year. Such events would seem to be spectacularly obvious, but they generally go unnoticed for a number of reasons: the majority of the Earth's surface is covered by water; a good portion of the land surface is uninhabited; and the explosions generally occur at relatively high altitude, resulting in a huge flash and thunderclap but no real damage.
Some have been observed. Noteworthy examples include the Sikhote-Alin Meteorite fall in Primorye, far eastern Russia, in 1947, and the Revelstoke fireball of 1965, which occurred over the snows of British Columbia, Canada. Another fireball blew up over the Australian town of Dubbo in April 1993, shaking things up but causing no harm.
Sooner or later our luck--or perhaps divine forebearance--will run out, and an inhabited region will be hit, perhaps a major city.
Posts: 3742 | Registered: Dec 2001
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posted
I think I saw that 1965 event. I was taking a walk on the campus of my university in southwestern Michigan about 9:30 p.m. or so, and saw about a quarter of the sky lit up in the northwest. It lasted for over a minute. I thought at first some chemical company was on fire. I was surprised when the light dimmed down to nothing after awhile. Only a few other students saw it; some even ridiculed me. News reports the next morning said there was a fireball apparently of a meteoric origin that had been seen over most of North America.
Posts: 3742 | Registered: Dec 2001
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posted
One Saturday night I was chatting with Richard Berg at around 4am and heard a tremendous explosion. I mentioned to him that someone blew something up without inviting me. Later I found out it was a meteoric event that many people saw all over the northern part of the state. They never did find a crater, though. Whether that means it hit in the trackless wilderness of Alabama, or whether it exploded in the air and didn't damage anything much on the ground, I don't know. They say the fireball lit up the whole sky. It definitely made an impressive boom.
Posts: 6246 | Registered: Aug 2004
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No damage expected. Should be a spectacular view, though.
"The fireball may be visible over much of northern Africa, the Middle East, and possibly even southern Europe."
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"The fireball, which could be brilliant, will travel west to east (from azimuth = 281 degrees) at a relative atmospheric impact velocity of 12.8 km/s and arrive at a very low angle (19 degrees) to the local horizon. It is very unlikely that any sizable fragments will survive passage through the Earth's atmosphere.
Objects of this size would be expected to enter the Earth's atmosphere every few months on average but this is the first time such an event has been predicted ahead of time. "
Posts: 968 | Registered: Sep 2003
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posted
Those of you who remember the Deep Impact mission from 2005, in which an impacting body was released to hit a comet, and who remember the mystery of how big the explosion was and how much stuff was liberated (more than 100 times as much as expected) might be interested in this article.
quote: [An astronomer] speculates that the impact must have punched through to a layer of water frozen as amorphous (not crystalline) ice. This form of ice is what theorists expect to find in comets that came together at temperatures below –190°F (–125° Celsius). [Another astronomer] explains that amorphous ice would rapidly convert to its crystalline form once exposed to space and liberate lots of heat.
That's an interesting theory. I wonder how much heat would be liberated.
Posts: 6246 | Registered: Aug 2004
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posted
Fascinating, Tatiana! Thanks for the update. Deep Impact was such a cool mission
T:man, I think that the consensus is that there is a very slight chance that the 2029 pass could alter the asteroid's trajectory so that it hits in 2036, but the current impact probability for that is 1 in 45,000. More observations over the next few years might let us rule out the possibility of a 2036 impact.
Posts: 3546 | Registered: Jul 2002
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As a guess, it's more likely the comet had a core of glassy*water held within a shell of ice Ih. And rather than ice being partially gassified and partially melted by the energy of impact with the melt water explosively decompressed (boiled off) as a result of exposure to the vacuum of space, most of the blow-off was the result of glassy water being squirted through the hole punched through the Ic shell by the impactor.
* ie The comet originated as amorphous ice. Then as the comet became warmed by the stronger sunlight during its inward plunge, the amorpheous surface ice transformed into a shell of regular ice. And (a significant portion of) the core Ic became sufficiently warm to transition into glassy water.
posted
If 100 times as much matter exploded outward than had been anticipated, perhaps a nuke could be able to blow apart an earthbound asteroid, enough so most of the pieces are small enough to burn up in the atmosphere. Or maybe a well-placed nuke could alter the course of the asteroid sufficiently to miss earth, aided by the rocket propulsion from the enhanced amount of ejected matter.
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Wow, aspectre! For a few minutes there my heart stopped.
Posts: 6246 | Registered: Aug 2004
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Blayne Bradley
unregistered
posted
quote:Originally posted by Ron Lambert: If 100 times as much matter exploded outward than had been anticipated, perhaps a nuke could be able to blow apart an earthbound asteroid, enough so most of the pieces are small enough to burn up in the atmosphere. Or maybe a well-placed nuke could alter the course of the asteroid sufficiently to miss earth, aided by the rocket propulsion from the enhanced amount of ejected matter.
unfortunately this is in violation of international treaties.
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I can see astronomers getting really excited about an impact being predicted in a few years. They call a press conference with these childish grins on their faces. "Ladies and gentlemen, within the next two years, my colleagues and I will have the opportunity to blow up an asteroid and save the Earth."
Posts: 959 | Registered: Oct 2005
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posted
Hardly. A true astronomer would insist that the asteroid be left unmolested, as test of the validity of their bolide impact theories if nothing else. And undoubtedly facinating new facts would be learned about the composition of asteroids as well as that of the crust of earth-like planets. Who knows, maybe even a bit of the mantle would be ejected for further study. Think of all the journal publications an impact could generate.
posted
Wow, that one's amazing. I can't tell if that's the same fireball shot from two different cameras or if it's two successive parts of the same meteor that has broken up.
posted
The astronomer Steven Ostro just died, who was studying near earth objects. Here is a comment he made on the 100th anniversary of the Tunguska event that I think would be of interest to readers of this thread. He was a cool guy and it's sad that he's gone.
Posts: 6246 | Registered: Aug 2004
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posted
If you want something else to worry about, the supervolcano under Yellowstone Park, if it blew, would have a caldera 40 miles wide (that is how large the underground chamber of molten magma is right now), and be hundreds of times more powerful than Mt. St. Helens when it blew. Say good-bye to Yogi. Scientists say past eruptions covered the ground deeply for nearly a thousand miles all around with volcanic dust. They also say the supervolcanoe is long overdue for another eruption. There was a special on the Discovery Channel a few months ago (it aired back in April of 2008), a fictional dramatization of this.
Posts: 3742 | Registered: Dec 2001
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posted
Tatiana, it is sad also that astronomer Eugene Shoemaker died. He was killed in a traffic accident in 1997. The asteroid bodies that struck Jupiter came from the asteroid he co-discovered, Shoemaker-Levy. He worked for the U.S. Geological Survey, and focused much of his attention on asteroids. He is said to have single-handedly created planetary science as a discipline distinct from astronomy.
Posts: 3742 | Registered: Dec 2001
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quote:If you want something else to worry about, the supervolcano under Yellowstone Park, if it blew, would have a caldera 40 miles wide (that is how large the underground chamber of molten magma is right now), and be hundreds of times more powerful than Mt. St. Helens when it blew. Say good-bye to Yogi. Scientists say past eruptions covered the ground deeply for nearly a thousand miles all around with volcanic dust. They also say the supervolcanoe is long overdue for another eruption. There was a special on the Discovery Channel a few months ago (it aired back in April of 2008), a fictional dramatization of this.
Last I heard, the odds of this happening were pretty slim. You'd think some seismic activity might precede an eruption of that magnitude, too.
Posts: 1813 | Registered: Apr 2001
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posted
Even if it did, not a whole hell of a lot we can do about it. A thousand miles around covers almost everything from Seattle to Dallas, give or take.
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