[meteorite-list] Meteorites on Mars
From: MexicoDoug_at_aol.com <MexicoDoug_at_meteoritecentral.com>
Date: Thu Apr 22 10:32:00 2004 Message-ID: <bb.3ab3b316.2d2e8c0b_at_aol.com> --part1_bb.3ab3b316.2d2e8c0b_boundary Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit It is En un mensaje con fecha 01/08/2004 1:22:45 AM Mexico Standard Time, cviau_at_beld.net escribe: > Ron makes a great point here. It follows that almost all meteorites on > Mars should produce some kind of crater and most would be vaporized... > Does anyone out there know what the terminal velocity ratio is for Mars? > > CharlyV Bad question, CharlyV. The bad answer is 5. You are assuming free fall terminal velocity is reached by Mars impacting meteorites, so it's a loaded question. And from the way I see it, loaded the wrong way. The question ain't so much what free fall terminal velocity "ratio" is. (Anyhow, that depends on object height and planet atmospheric scale height, just like on Earth, so it ain't a linear factor from what I would theorize Charly, ask a skydiver or better yet Captain K who did the big jump in the 1950's or so and some say did and some say did and others didn't break the sound barrier. He didn't but he was real close. That would be six times a typical terminal velocity at sea level. on Earth. And he just jumped off a gondola at 100,000 feet or so (Same thiness as Mars at ground zero, how coincidental:) For the kind of meteoric stuff falling in the Sahara I get a factor of about 5 times faster, from a crap load of assumptions, even if I consider it a bad question, I picked an answer to please (based on pizza sized assumptions). And there were plenty of assumptions which while you can have a simple number really isn't very useful, because: You want to know IF it slows to free fall terminal velocity, and the answer is probably NO, except for pretty small stuff, not big crater stuff anyway. I'll leave you to do the cross sectional area and mass for that calculation to see exactly how small. Then the reality may really depend on the initial velocity and angle of incidence of the meteorite to see how much it is slowed. Oh...there the bolides won't be exploding at 20 km high like here on Earth, which handily increased the braked by multing cross sectional area hugely. The SURFACE of Mars has similar density to Earth at something around 30 km height (100,000 feet = 20 miles), so if it explodes too much below that on Earth, it won't explode at all on Mars. The density is just not there. So expect big flaming rocks to smash Mars and make craters, unless the incredible Hulk is there to play ball. The calculations to the 5 times factor were: Just by assuming the martian g force to be 3.7 m/s/s and Earth's 9.8 m/s/s (Mars' g force is only about 38% ours) causing a slower free fall velocity. Also, if Mars is mainly carbon dioxide (molecular wt. is 44) and we nitrogen (molecular wt. 28), there will be an additional density about 50% greater 44/28, as well as an increased density of another 30% extra because Mars is colder (300K/230K) absolute temperature ratio based on PV=RT, and finally molecular concentrations at ground level, the famous less than 1%, more accurately factor of about 0.8%. In summary, it's a g force is proportional to velocity squared, so g-velocity factor: sqrt(0.38) and inversely proportion of atmospheric density to velocity squared, sqrt((1.5)(1.3)(0.01)) So if terminal velocity is reached Mars is loaded with puzzle meteorites, sometimes with thousands of itsy bitsy pieces. Solving, sqrt(0.38/1.5/1.3/0.008) = 4.9 times Earth terminal velocity, for a pizza sized cross sectional area. Call it an even five. And that's for igneous, not iron. Iron would be 2 to 3 times as fast. But as already stated...the atmosphere is real thin to damp all that momentum in most cases. My thoughts Charly. They are not guaranteed, but good enough for government work. Saludos, Doug Dawn Mexico > > > -----Original Message----- > From: meteorite-list-admin_at_meteoritecentral.com > [mailto:meteorite-list-admin_at_meteoritecentral.com] On Behalf Of Ron > Baalke > Sent: Wednesday, January 07, 2004 4:39 PM > To: Meteorite Mailing List > Subject: Re: [meteorite-list] Meteorites on Mars > > >1. Mars' thinner atmosphere means more > >meteorites survive the fall though it > >than on Earth. > > There are a number of factors to consider. Mars is smaller > than Earth, so has less gravity to pull in meteoroids. > However, Mars is closer to the asteroid belt, so is more > likely to encounter meteoroids than Earth. The thinner atmosphere means > it is more likely a meteorite will reach the surface, but it > also means it is more likely to impact at hypervelocity > speeds, and hypervelocity impacts tends to totally > vaporize meteorites. > > Ron Baalke > > ______________________________________________ > Meteorite-list mailing list > Meteorite-list_at_meteoritecentral.com > http://www.pairlist.net/mailman/listinfo/meteorite-list > --part1_bb.3ab3b316.2d2e8c0b_boundary Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable <HTML><FONT FACE=3Darial,helvetica><HTML><FONT SIZE=3D2 PTSIZE=3D10 FAMILY= =3D"SANSSERIF" FACE=3D"Arial" LANG=3D"0">It is En un mensaje con fecha 01/08= /2004 1:22:45 AM Mexico Standard Time, cviau_at_beld.net escribe:<BR> <BR> <BLOCKQUOTE TYPE=3DCITE style=3D"BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT= : 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px">Ron makes a great point here. I= t follows that almost all meteorites on<BR> Mars should produce some kind of crater and most would be vaporized...<BR> Does anyone out there know what the terminal velocity ratio is for Mars?<BR> <BR> CharlyV</BLOCKQUOTE><BR> <BR> Bad question, CharlyV. The bad answer is 5. You are assuming fre= e fall terminal velocity is reached by Mars impacting meteorites, so it's a=20= loaded question. And from the way I see it, loaded the wrong way. = ; The question ain't so much what free fall terminal velocity "ratio" is.&nb= sp; (Anyhow, that depends on object height and planet atmospheric scale heig= ht, just like on Earth, so it ain't a linear factor from what I would theori= ze Charly, ask a skydiver or better yet Captain K who did the big jump in th= e 1950's or so and some say did and some say did and others didn't break the= sound barrier. He didn't but he was real close. That would be s= ix times a typical terminal velocity at sea level. on Earth. And he ju= st jumped off a gondola at 100,000 feet or so (Same thiness as Mars at groun= d zero, how coincidental:)<BR> <BR> For the kind of meteoric stuff falling in the Sahara I get a factor of about= 5 times faster, from a crap load of assumptions, even if I consider it a ba= d question, I picked an answer to please (based on pizza sized assumptions).= And there were plenty of assumptions which while you can have a simpl= e number really isn't very useful, because:<BR> <BR> You want to know IF it slows to free fall terminal velocity, and the answer=20= is probably NO, except for pretty small stuff, not big crater stuff anyway.&= nbsp; I'll leave you to do the cross sectional area and mass for that calcul= ation to see exactly how small. Then the reality may really depend on=20= the initial velocity and angle of incidence of the meteorite to see how much= it is slowed. Oh...there the bolides won't be exploding at 20 km high= like here on Earth, which handily increased the braked by multing cross sec= tional area hugely. The SURFACE of Mars has similar density to Earth a= t something around 30 km height (100,000 feet =3D 20 miles), so if it explod= es too much below that on Earth, it won't explode at all on Mars. The=20= density is just not there. So expect big flaming rocks to smash Mars a= nd make craters, unless the incredible Hulk is there to play ball.<BR> <BR> The calculations to the 5 times factor were:<BR> <BR> Just by assuming the martian g force to be 3.7 m/s/s and Earth's 9.8 m/s/s (= Mars' g force is only about 38% ours) causing a slower free fall velocity.&n= bsp; Also, if Mars is mainly carbon dioxide (molecular wt. is 44) and we nit= rogen (molecular wt. 28), there will be an additional density about 50% grea= ter 44/28, as well as an increased density of another 30% extra because Mars= is colder (300K/230K) absolute temperature ratio based on PV=3DRT, and fina= lly molecular concentrations at ground level, the famous less than 1%, more=20= accurately factor of about 0.8%. <BR> <BR> In summary, it's a g force is proportional to velocity squared, so g-velocit= y factor: sqrt(0.38) and inversely proportion of atmospheric density to velo= city squared, sqrt((1.5)(1.3)(0.01)) So if terminal velocity is=20= reached Mars is loaded with puzzle meteorites, sometimes with thousands of i= tsy bitsy pieces.<BR> <BR> Solving, sqrt(0.38/1.5/1.3/0.008) =3D 4.9 times Earth terminal velocity, for= a pizza sized cross sectional area. Call it an even five. And t= hat's for igneous, not iron. Iron would be 2 to 3 times as fast. = But as already stated...the atmosphere is real thin to damp all that moment= um in most cases.<BR> <BR> My thoughts Charly. They are not guaranteed, but good enough for gover= nment work.<BR> Saludos,<BR> Doug Dawn<BR> Mexico<BR> <BR> <BR> <BR> <BR> <BLOCKQUOTE TYPE=3DCITE style=3D"BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT= : 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px"><BR> <BR> -----Original Message-----<BR> From: meteorite-list-admin_at_meteoritecentral.com<BR> [mailto:meteorite-list-admin_at_meteoritecentral.com] On Behalf Of Ron<BR> Baalke<BR> Sent: Wednesday, January 07, 2004 4:39 PM<BR> To: Meteorite Mailing List<BR> Subject: Re: [meteorite-list] Meteorites on Mars<BR> <BR> >1. Mars' thinner atmosphere means more <BR> >meteorites survive the fall though it <BR> >than on Earth.<BR> <BR> There are a number of factors to consider. Mars is smaller<BR> than Earth, so has less gravity to pull in meteoroids. <BR> However, Mars is closer to the asteroid belt, so is more<BR> likely to encounter meteoroids than Earth. The thinner atmosphere mean= s<BR> it is more likely a meteorite will reach the surface, but it<BR> also means it is more likely to impact at hypervelocity<BR> speeds, and hypervelocity impacts tends to totally <BR> vaporize meteorites.<BR> <BR> Ron Baalke<BR> <BR> ______________________________________________<BR> Meteorite-list mailing list<BR> Meteorite-list_at_meteoritecentral.com<BR> http://www.pairlist.net/mailman/listinfo/meteorite-list<BR> </BLOCKQUOTE><BR> <BR> </FONT></HTML> --part1_bb.3ab3b316.2d2e8c0b_boundary-- Received on Thu 08 Jan 2004 05:33:47 AM PST |
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