[meteorite-list] NP Article, 11-1965 Meteorite Craters

From: MARK BOSTICK <thebigcollector_at_meteoritecentral.com>
Date: Thu Apr 22 10:28:25 2004
Message-ID: <BAY4-DAV625ZmrylLGP00001ec1_at_hotmail.com>

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Paper: Nevada State Journal
City: Reno, Nevada
Date: Sunday, November 07, 1965
Page: 34

By Prof. Wendell A. Mordy
Director Desert Research Institute, University of Nevada, Reno

Last summer, the Mariner 4 photographs showed the surface of Mars is cove=
red with craters, like those on the moon. The craters apparently are caus=
ed by giant meteorites colliding with the planet.
Some scientist think this is an indication that meteorites bombard all bo=
dies in the solar system, including the earth. Dr. Frank Dachille, associ=
ate professor of Geochemistry at the Pennsylvania State University, think=
s that there are many such craters on earth. The outlines of most of them=
 has been softened by erosion, or covered by vegetation or water, accordi=
ng to Dachille.
He is co-author of a highly controversial book on the evolution of Earth,=
 called "Target Earth." In that book he lists more than 70 huge depressio=
ns on earth which he thinks problably were caused by meteorite impacts. T=
he list includes the entire Michigan Basin, the Wells Creek Basin in Tenn=
essee, and many others, in addition to depressions such as Meteor Crater =
in Arizona, Deep Bay in Canada, and the tiny Odessa Crater in Texas, whic=
h are more obvious and which scientists pretty generally agree were forme=
d by meteorite bombardments.

'Falling Stars'

Small meteorites frequently hit the earth, and are recognized as "falling=
 stars." Occasionally small fragments are found. It takes only about 1,00=
0 years for rain, snow, food, fire, earthquakes, plants, animals and othe=
r influences to destroy the traces of the impact of sizeable meteors, acc=
ording to Dachille.
Dachille estimates that the million meteors which have hit the earth duri=
ng the last 5 billion years, the traces of probably not more than 250 rem=
ain sufficiently preserved to be recognized, even by aeriel photographs, =
or eventually satellite photographs.
However, there are other ways to discover the location of hits by meteori=
tes, according to Dachille. Dachille and his colleagues have found minera=
ls from suspected crater sites outwordly appearing as if they were hardly=
 damaged, but with their crystal structure so highly deformed that they w=
ere actually powder, rather then crystals as determined by X-ray.
Dachille is experimenting to create laboratory conditions approaching tho=
se which must occur when a large body crashes into the earth. He says, "M=
inerals showing severe crystal damage coming from suspected craters, in c=
ontrast with those from surrounding rocks, support the hyprothesis that t=
he craters were formed by meteorites."
A meteorite which can dig a crater 300 miles in diameter would have to be=
 about 30 or 40 miles in diameter, he estimates. Bodies this size could b=
e quite common in the solar system, and would represent 10 billion times =
the amount of energy released by the first atomic bombs.
Disappears

When such a large meteorite hits the Earth, it is vaporized and completel=
y disappears, he says, just as fragments of superbombs don't survive.
Since there is no water or growth on the moon to gradually remove the sca=
rs of meteorite impacts, about 60,000 circular scars, some of which are h=
undreds of miles across, still can be seen on the moon.
Dachille says there is no reason to think that the earth could have avoid=
ed the kind of bombardment which has occurred on the Moon and Mars. Three=
 large bodies, with energies as large as the Hudson Bay Meteorite have pa=
ssed within a few miles of Earth since the turn of the century, Dachille =
points out.
There is no reason to think that some of this size wouldn't have struck t=
he earth during its lifetime. He estimates that giant meteorites, like th=
e ones which have formed the Gulf of St. Lawrence or part of Hudson's Bay=
, only happen once in 10 million years or so.
He thinks that lunar explorations will teach us a lot about dating the fo=
rmation of craters, and the mechanism which created them. In the meantime=
, he says, "It should be useful as well as instructive at least to consid=
er the possible effects of large collisions - throughout the solar system=
."


Please visit, www.MeteoriteArticles.com, a free on-line archive of meteor=
 and meteorite articles.

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<HTML><BODY STYLE=3D"font:10pt verdana; border:none;"><DIV><B><FONT size=3D=
2> <P>Paper: Nevada State Journal</P> <P>City: Reno, Nevada</P> <P>Date: =
Sunday, November 07, 1965</P> <P>Page: 34</P></B> <P>&nbsp;</P> <P>By Pro=
f. Wendell A. Mordy</P> <P>Director Desert Research Institute, University=
 of Nevada, Reno</P> <P>&nbsp;</P> <P>Last summer, the Mariner 4 photogra=
phs showed the surface of Mars is covered with craters, like those on the=
 moon. The craters apparently are caused by giant meteorites colliding wi=
th the planet.</P> <P>Some scientist think this is an indication that met=
eorites bombard all bodies in the solar system, including the earth. Dr. =
Frank Dachille, associate professor of Geochemistry at the Pennsylvania S=
tate University, thinks that there are many such craters on earth. The ou=
tlines of most of them has been softened by erosion, or covered by vegeta=
tion or water, according to Dachille.</P> <P>He is co-author of a highly =
controversial book on the evolution of Earth, called "Target Earth." In t=
hat book he lists more than 70 huge depressions on earth which he thinks =
problably were caused by meteorite impacts. The list includes the entire =
Michigan Basin, the Wells Creek Basin in Tennessee, and many others, in a=
ddition to depressions such as Meteor Crater in Arizona, Deep Bay in Cana=
da, and the tiny Odessa Crater in Texas, which are more obvious and which=
 scientists pretty generally agree were formed by meteorite bombardments.=
</P> <P>&nbsp;</P> <P>'Falling Stars'</P> <P>&nbsp;</P> <P>Small meteorit=
es frequently hit the earth, and are recognized as "falling stars." Occas=
ionally small fragments are found. It takes only about 1,000 years for ra=
in, snow, food, fire, earthquakes, plants, animals and other influences t=
o destroy the traces of the impact of sizeable meteors, according to Dach=
ille.</P> <P>Dachille estimates that the million meteors which have hit t=
he earth during the last 5 billion years, the traces of probably not more=
 than 250 remain sufficiently preserved to be recognized, even by aeriel =
photographs, or eventually satellite photographs.</P> <P>However, there a=
re other ways to discover the location of hits by meteorites, according t=
o Dachille. Dachille and his colleagues have found minerals from suspecte=
d crater sites outwordly appearing as if they were hardly damaged, but wi=
th their crystal structure so highly deformed that they were actually pow=
der, rather then crystals as determined by X-ray.</P> <P>Dachille is expe=
rimenting to create laboratory conditions approaching those which must oc=
cur when a large body crashes into the earth. He says, "Minerals showing =
severe crystal damage coming from suspected craters, in contrast with tho=
se from surrounding rocks, support the hyprothesis that the craters were =
formed by meteorites."</P> <P>A meteorite which can dig a crater 300 mile=
s in diameter would have to be about 30 or 40 miles in diameter, he estim=
ates. Bodies this size could be quite common in the solar system, and wou=
ld represent 10 billion times the amount of energy released by the first =
atomic bombs.</P> <P></P> <P>Disappears</P> <P>&nbsp;</P> <P>When such a =
large meteorite hits the Earth, it is vaporized and completely disappears=
, he says, just as fragments of superbombs don't survive.</P> <P>Since th=
ere is no water or growth on the moon to gradually remove the scars of me=
teorite impacts, about 60,000 circular scars, some of which are hundreds =
of miles across, still can be seen on the moon.</P> <P>Dachille says ther=
e is no reason to think that the earth could have avoided the kind of bom=
bardment which has occurred on the Moon and Mars. Three large bodies, wit=
h energies as large as the Hudson Bay Meteorite have passed within a few =
miles of Earth since the turn of the century, Dachille points out.</P> <P=
>There is no reason to think that some of this size wouldn't have struck =
the earth during its lifetime. He estimates that giant meteorites, like t=
he ones which have formed the Gulf of St. Lawrence or part of Hudson's Ba=
y, only happen once in 10 million years or so.</P> <P>He thinks that luna=
r explorations will teach us a lot about dating the formation of craters,=
 and the mechanism which created them. In the meantime, he says, "It shou=
ld be useful as well as instructive at least to consider the possible eff=
ects of large collisions - throughout the solar system."</P></FONT><BR><B=
R>Please visit, www.MeteoriteArticles.com, a free on-line archive of mete=
or and meteorite articles.</DIV></BODY></HTML>

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Received on Sat 11 Oct 2003 02:44:44 PM PDT