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The small planetesimals of our SolarSystem are


Are they Good or Bad?

| Eros | Mathilde| FX11 |


Good Asteroids might be Gold Mines.

BBCNews Online Science Editor Dr David Whitehouse wrote, on 22 July1999:

"The most detailed study of an asteroid shows that it containsprecious metals worth at least $20,000bn. The data were collectedlast December by the Near Earth Asteroid Rendezvous (Near) spacecraftwhich passed close to the asteroid Eros. ... Thefirst conclusions from that encounter are now published the journalScience. ... Eros is believed to have been formed from the wreckageof a collision with a larger body. Its composition appears to besimilar to the stony meteorites that frequently fall to Earth. Thatmeans Eros is a goldmine in space, as well as aplatinum mine, a zinc mine and many more minerals besides.

If Eros is typical of stony meteorites,then it contains about 3% metal. With the known abundance's ofmetals in meteorites, even a very cautious estimate suggests 20,000million tonnes of aluminium along with similar amounts of gold,platinum and other rarer metals. In the 2,900 cubic kms ofEros, there is more aluminium,gold, silver, zinc and other base and precious metals than have everbeen excavated in history or indeed, could ever be excavated from theupper layers of the Earth's crust.

That is just in one asteroid and not a very large one at that. ...How much is Eros worth? Today's trading price for gold is about $250per ounce or about $9m per tonne. It means the value of the gold inasteroid Eros is about $1,000bn. That is just the gold. Platinum iseven more expensive, $350 per oz. Work it out yourself. Since itcontains a lot of rare elements and metals that are of use in thesemiconductor industry for example, at today's prices Eros is worthmore than $20,000bn. ... One way to get the metals back would be tomine them on Eros and send the refined iron back to Earth. ...

It takes about 2,000 calories to boil a gram of iron so theequivalent of between 20 to 200 thousand megatons of TNT would beneeded to start liberating substantial quantities of iron from theasteroid. But this energy could be obtained from the Sun. If youwanted to mine only a section of Eros at a time then a huge solarenergy collector - a sheet only a few kilometres in size - couldcollect enough energy from sunlight to power a smelting plant on thesurface of Eros. These are all "guesstimate" figures. But they serveto demonstrate just how plentiful are the resources of the SolarSystem, in terms of minerals, metals and energy, once we decide to goout and get them. It shows how mining one fairly small asteroid likeEros would revolutionise the availability of many raw materials onEarth. ...


Bad Asteroids might Collidewith Earth.


According to a 24 July 2002 BBCarticle by David Whitehouse and by Ivan Noble: "...

A preliminary orbit suggests that ... asteroid ... 2002NT7 is on an impact course with Earth and could strike the planet on1 February, 2019 - although the uncertainties are large.

... [ This image

is from a 24 July BBCarticle by Ivan Noble. ] ...

... It was first seen on the night of 5 July, picked up by theLinear Observatory's automated sky survey programme in New Mexico,US. ... NT7 circles the Sun every 837 days and travels in a tiltedorbit ...[that]... is rather highly inclined to the Earth'sorbit ... from about the distance of Mars to just within the Earth'sorbit. ... NT7 will be easily observable for the next 18 months or so... Observations made over that period - and the fact that NT7 isbright enough that it is bound to show up in old photographs - meanthat scientists will soon have a very precise orbit for the object.... From its brightness, astronomers estimate it is about twokilometres wide ... Researchers estimate that on 1 February, 2019,its impact velocity on the Earth would be 28 km a second - enough towipe out a continent and cause global climate changes. ...".



According to a 23 December 2000 BBCarticle: "...

An asteroid capable of wiping out a city has missed theEarth by an astronomical whisker.

The 50-yard space rock travelled over London at more than20 miles per second before missing the planet by just 480,000 miles -twice the distance to the moon but a near miss in astronomical terms.If it had collided with Earth it would have left a hole threequarters of a mile across. The asteroid, still visible through areasonably powerful telescope in the constellation of Ophiuchus,appeared without warning above the capital at 2400GMT onFriday [22 December 2000]. Robin Scagell, vice-presidentof the Society for Popular Astronomy, said astronomers can trackkilometre-wide asteroids - but spotting smaller objects is muchharder. ... he said. "Now with the advanced image detectors availabletoday we are beginning to realise that we're in a bit of a shootinggallery." The asteroid ... has been given the name 2000 YA ...Professor Duncan Steel, the author of Target Earth - a book aboutasteroids, told the BBC Radio 4's Today programme: "The last time theEarth was hit by something like this was in 1908 above Siberia. "Itreleased energy equivalent to about 20 megatonnes of TNT. If it wasto enter the atmosphere above London, it would take out the whole ofthe city out to the M25." ...".


Could Asteroid 1997 FX11 hit Earth on 26 October 2028?

According to an AssociatedPress article by Paul Recer on 11 March 1998:

"... Asteroid 1997 XF11 was discovered Dec. 6 by the University ofArizona Spacewatch program and was added to a list of 108 asteroidsconsidered to be "potentially hazardous objects." ...[Asteroid] specialist Jack G. Hills said the space rock ...poses a real danger to Earth. ... Steven Maran of the AmericanAstronomical Society ... noted that no asteroid the size of 1997 XF11has ever been predicted to pass so close to the Earth. Hills said anasteroid the size of 1997 XF11 colliding with the Earth at more than17,000 miles an hour would explode with an energy of about 320,000megatons of dynamite. That equals almost 2 million Hiroshima-sizedatomic bombs. Such an asteroid hitting the ocean, said Hills, wouldcreate a tidal wave hundreds of feet high, causing extreme floodingfor thousands of miles of coast line. "If one like this hit in theAtlantic Ocean, all of the coastal cities would be scoured by thetsunami," said Hills. "Where cities stood, there would be onlymudflats." If such an asteroid hit on land, he said, it wouldinstantly dig a crater 20 miles across and so clog the sky with dustand vapor that the sun would be darkened "for weeks, if not months."Maran said the best estimate is that the mile-wide 1997 XF11 willpass inside the orbit of the moon, with the most likely separationfrom the center of the Earth of about 30,000 miles. The Earth has aradius of about 4,000 miles. The estimate, said Maran, has a marginof error of more than 180,000 miles. This means a collision withEarth is theoretically possible, but uncertain at this time, he said.... Observations made earlier this month by University of Texasastronomers indicated the asteroid would make its nearest approach tothe Earth on Oct. 26, 2028, at about 1:30 p.m. EDT. ... The noticesaid the asteroid, which is on a wide-swinging, independent orbit ofthe sun, will move out of view to all but the largest telescopes overthe next few months. It will become more visible once again in 2000.And in 2002, it is expected to pass within about 6 million miles ofEarth on Halloween Eve. Hills said the asteroid is lost from viewwhen it passes behind the sun, but that it will emerge into telescoperange about every two years. Astronomers eventually will be able totrack the object using radar, he said, and this will enable them toestablish a precise orbital path years ahead of the possible impact.Only then, said Hills, will the true risk of collision be known.Experts long concerned about the potential danger of asteroids havesaid the Earth could be protected by exploding a missile near thespeeding rock while it was far away. The intent would be to nudge theasteroid onto a path that would send it safely away from the planet.... "



According to the Erosdescription in the web pages ofthe NEAR (Near Earth Asteroid Rendezvous) program, one of thelargest and best observed near-Earth asteroids is 433 Eros,discovered in 1898 independently by G. Witt (Germany) and A. Chalois(France). Eros accounts for half of the volume of all near-Earthasteroids. The potato-shaped Eros is one of the most elongatedasteroids, with estimated dimensions of 35 x 15 x 13 kilometers, soit almost fits within the Baltimore Beltway. Eros orbits around theSun with a perihelion of 1.13 AU (169,045,593 km) and 1.78 AU(266,284,209 km), and it rotates once every 5.27 hours. Though it isan S type asteroid, it is somewhat varied in its chemicalcomposition. Its opposite sides have slightly different mineralogies.The gravity on Eros is very weak but enough to hold a spacecraft.There is no air and no evidence of water. The day time temperature ofEros is about 100 C while at night in plunges to -150 C.

This montage of the asteroid Eros was assembled from imagesacquired by the Near Earth Asteroid Rendezvous (NEAR) spacecraft onDec. 23, as the spacecraft flew by the asteroid at a distance of2,500 miles (4,100 kilometers) at 1:43 p.m. EST. This montage showsthe first nine of 28 views of Eros that were obtained during theflyby. The images were taken between 10:44 AM and 12:44 PM EST as thespacecraft range closed from 7300 miles (11,100) km to 3300 miles(5300 kilometers). During that time, the asteroid completed nearlyhalf of a rotation. The smallest resolved detail is approximately1650 feet (500 meters) across. ... Options for rescheduling firing ofthe main spacecraft engine are currently being examined, and couldlead to Eros rendezvous and orbit insertion as early as mid-1999 oras late as May 2000. Eros is NEAR's second asteroid encountered. OnJune 27, 1997, NEAR flew by the main-belt asteroid Mathilde at arange of 1212 kilometers (750 miles).



According to the Mathildeinformation in the web pages ofthe NEAR (Near Earth Asteroid Rendezvous) program, asteroid 253Mathilde has been sstudied by scientists in the Science Data Centerat the Johns Hopkins University Applied Physics Laboratory in Laurel,Md.

A 25-minute flyby of the asteroid by the Near Earth AsteroidRendezvous (NEAR) spacecraft on June 27 has resulted in spectacularimages of a dark, crater-battered little world assumed to date fromthe beginning of the solar system. The Mathilde flyby is the closestencounter with an asteroid to date and the first with a C-typeasteroid. The asteroid's mean diameter was found to be 33 miles (52kilometers), which is somewhat smaller than researchers originallyestimated. A study of the asteroid's albedo (brightness or reflectivepower) shows that it reflects three percent of the sun's light,making it twice as dark as a chunk of charcoal. Such a dark surfaceis believed to consist of carbon-rich material that has not beenaltered by planet-building processes, which melt and mix up the solarsystem's original building block materials.



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