[meteorite-list] Lunar velocities...
From: Darryl S. Futrell <futrelds_at_meteoritecentral.com>
Date: Thu Apr 22 09:44:44 2004 Message-ID: <024d01c0b9a4$87281520$05e41e3f_at_pavilion> This is a multi-part message in MIME format. ------=_NextPart_000_0154_01C0B953.E4F290A0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable -----Original Message----- From: Robert Beauford <wendirob_at_laplaza.org> To: meteorite-list_at_meteoritecentral.com = <meteorite-list_at_meteoritecentral.com> Date: Tuesday, March 27, 2001 10:50 AM Subject: [meteorite-list] Lunar velocities... =20 =20 How could such a tektite have a lunar origin? Easy. Within seconds = after leaving the moon, all splashform tektites became cold rigid = bodies. They all entered our atmosphere as cold rigid bodies. (All = layered tektites were fragmented cold, or a least cool, rigid bodies = when they left the moon. Tektite glass is a very good heat shield = material (Chapman discussed this). The higher the alumina content, the = more durable. In any case, many Indochinites, and other Australasian = splashform tektites do show slight ablation evidence, unless they have = been too eroded by terrestrial weathering, and most have. Any = stretching or bending occurred in the first few seconds after = splashforms left the lunar surface and were still soft. Some collisions = must have taken place at that time. =20 DSF =20 =20 "These "stretch" tektites are a clear indication of terrestrial = origin as how could such a form survive if they had been formed on the = moon and then entered the Earth's atmosphere at 7+ miles per/sec?" =20 Steve's comment above got me curious. It seems like ejecta from the = moon need not reach a cosmic velocity or earth orbital velocity, just an = escape velocity or orbital velocity of the moon. It seems, more = specifically, that any fragment with a speed over the escape velocity of = the moon, and a vector that points it inside the orbit of the moon = around the earth (slightly less than 50% of all lunar ejecta?), and = insufficient residual speed to send it back out of that orbit, would = fall to earth. This should alow for some very slow objects reaching = earth (and thus less ablation loss and entry alteration) What is this = necessary and maximum speed? Please note, I am not advocating a lunar = origin for tektites, just idly, and perhaps ignorantly, wondering if = lunar meteorites might enter the atmosphere slower than some other = meteorites. -Robert Beauford : ) =20 ------=_NextPart_000_0154_01C0B953.E4F290A0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable <!DOCTYPE HTML PUBLIC "-//W3C//DTD W3 HTML//EN"> <HTML> <HEAD> <META content=3Dtext/html;charset=3Diso-8859-1 = http-equiv=3DContent-Type><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 = Transitional//EN"> <META content=3D'"MSHTML 4.72.3110.7"' name=3DGENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=3D#ffffff> <DIV> </DIV> <BLOCKQUOTE=20 style=3D"BORDER-LEFT: #000000 solid 2px; MARGIN-LEFT: 5px; PADDING-LEFT: = 5px"> <DIV><FONT face=3DArial size=3D2><B>-----Original = Message-----</B><BR><B>From:=20 </B>Robert Beauford <<A=20 = href=3D"mailto:wendirob_at_laplaza.org">wendirob@laplaza.org</A>><BR><B>T= o:=20 </B><A=20 = href=3D"mailto:meteorite-list_at_meteoritecentral.com">meteorite-list@meteor= itecentral.com</A>=20 <<A=20 = href=3D"mailto:meteorite-list_at_meteoritecentral.com">meteorite-list@meteor= itecentral.com</A>><BR><B>Date:=20 </B>Tuesday, March 27, 2001 10:50 AM<BR><B>Subject: = </B>[meteorite-list]=20 Lunar velocities...<BR><BR></DIV></FONT> <DIV><FONT size=3D2></FONT><FONT color=3D#000000=20 face=3D"Arial Rounded MT Bold">How could such a tektite have a lunar = origin? Easy. Within seconds after leaving the moon, all = splashform tektites became cold rigid bodies. They all entered = our=20 atmosphere as cold rigid bodies. (All layered tektites were = fragmented=20 cold, or a least cool, rigid bodies when they left the moon. = Tektite=20 glass is a very good heat shield material (Chapman discussed = this). =20 The higher the alumina content, the more durable. In any case, = many=20 Indochinites, and other Australasian splashform tektites do show = slight=20 ablation evidence, unless they have been too eroded by terrestrial=20 weathering, and most have. Any stretching or bending occurred = in the=20 first few seconds after splashforms left the lunar surface and were = still=20 soft. Some collisions must have taken place at that = time.</FONT></DIV> <DIV><FONT color=3D#000000 face=3D"Arial Rounded MT = Bold"></FONT> </DIV> <DIV><FONT face=3D"Arial Rounded MT Bold">DSF</FONT></DIV> <DIV><FONT size=3D2></FONT> </DIV> <DIV><FONT size=3D2></FONT> </DIV> <DIV><FONT size=3D2>"These "stretch" tektites are a = clear=20 indication of terrestrial origin as how could such a form survive if = they=20 had been formed on the moon and then entered the Earth's atmosphere = at 7+=20 miles per/sec?"</FONT></DIV> <DIV><FONT size=3D2></FONT> </DIV> <DIV><FONT size=3D2>Steve's comment above got me curious. It = seems like=20 ejecta from the moon need not reach a cosmic velocity or earth = orbital=20 velocity, just an escape velocity or orbital velocity of the = moon. It=20 seems, more specifically, that any fragment with a speed over the = escape=20 velocity of the moon, and a vector that points it inside = the orbit=20 of the moon around the earth (slightly less than 50% of all = lunar=20 ejecta?), and insufficient residual speed to send it back out of = that orbit,=20 would fall to earth. This should alow for some very slow = objects=20 reaching earth (and thus less ablation loss and entry = alteration) What=20 is this necessary and maximum speed? Please note, I am not = advocating=20 a lunar origin for tektites, just idly, and perhaps ignorantly, = wondering if=20 lunar meteorites might enter the atmosphere slower than some other=20 meteorites.</FONT></DIV> <DIV><FONT size=3D2>-Robert Beauford :=20 )<BR><BR></DIV></FONT></BLOCKQUOTE></BODY></HTML> ------=_NextPart_000_0154_01C0B953.E4F290A0-- Received on Fri 30 Mar 2001 10:59:14 PM PST |
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