Re: [meteorite-list] Venusian meteorites
Hi, Earlier today MikeG, Chris and I were kind of wondering about Venusian meteorites. I looked back at the archives and found a bit of discussion already between Sterling, Elton, Tracy, Howard, Mike F. and Mark F. on the subject. This discussion was way back in 2003, before my time, but it seems the questions are still out there. This interesting discussion may be worth another look. See links to the archives here: http://meteorite-identification.com/mwnews/BLECKENSTAD.htm http://www.mail-archive.com/meteorite-list@meteoritecentral.com/msg16223.html http://www.mail-archive.com/meteorite-list@meteoritecentral.com/msg16211.html Carl2 __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Venusian meteorites
Hi Mike, Chris and list, I've often wondered the same thing. Were there any studies on matching the Venusian atmosphere to some ungrouped achondrites or other meteorites, similar to gases trapped in Martian meteorites to it's atmosphere? Thanks! Carl2 MikeG wrote: >...I am going to take a wild layman stab at this one and then Sterling Webb can come in and clean up my mess. ;) LOL All of the confirmed planetary meteorites we have seen (barring the disputed Angrite-Mercury connection) come from planets further out from the sun than Earth. So I am guessing that maybe the Sun's gravitational influence would have more effect on a Venusian rock that manages to escape that acidic and hellish world... Chris wrote: Where the Venusian meteorites? __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Venusian meteorites
Hi Chris and List, I am going to take a wild layman stab at this one and then Sterling Webb can come in and clean up my mess. ;) LOL All of the confirmed planetary meteorites we have seen (barring the disputed Angrite-Mercury connection) come from planets further out from the sun than Earth. So I am guessing that maybe the Sun's gravitational influence would have more effect on a Venusian rock that manages to escape that acidic and hellish world. Perhaps the gravitational perturbations introduced by Venus' proximity to Sol make it less likely that a Venusian fragment would cross paths with Earth? And perhaps the very nature of Venus' atmosphere make it less likely for such rocks to achieve escape velocity and survive the trip out of the acid bath. Best regards, MikeG On 9/9/10, Chris Spratt wrote: > Where the Venusian meteorites? > > Chris Spratt > Victoria, BC > (Via my iPhone) > __ > Visit the Archives at > http://www.meteoritecentral.com/mailing-list-archives.html > Meteorite-list mailing list > Meteorite-list@meteoritecentral.com > http://six.pairlist.net/mailman/listinfo/meteorite-list > -- -- Mike Gilmer - Galactic Stone & Ironworks Meteorites Website - http://www.galactic-stone.com Facebook - http://www.facebook.com/galacticstone News Feed - http://www.galactic-stone.com/rss/126516 Twitter - http://twitter.com/galacticstone EOM - http://www.encyclopedia-of-meteorites.com/collection.aspx?id=1564 --- __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] Venusian meteorites
Where the Venusian meteorites? Chris Spratt Victoria, BC (Via my iPhone) __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] Venusian Meteorites (Again) and Mercury Too!
Hi, Another interesting aspect of getting Venus rocks to land on Earth is the orbit (or orbits) required to do it. Since Venus orbits closer to the Sun than the Earth, its orbital velocity (35,000 m/sec) is greater than the Earth's (29,800 m/sec). While there are a large variety of orbits which might allow a Venus rock to whack the Earth, the orbit most likely to deliver Venus rocks to the Earth is the minimum energy one. That's a cotangential elipse (called a Hohmann orbit after Dr. Hohmann who wrote the book on interplanetary flight back in 1925). It's an elipse that just touches the orbit of Venus at its closest to the Sun and just touches or barely passes the orbit of the Earth at its furthest. Once we've knocked that rock off Venus, it's moving at the Venus orbital speed (35,000 m/sec). To swing out further into the solar system to get as far as to Earth, it needs to be speeded up to 37,700 m/sec. Which is another way of saying that the only Venus rocks to reach the Earth have to leave Venus FASTER than the Venusian escape velocity, with a residual velocity of 2700 m/sec pointed in more or less the right direction. Ho Hum, you say. Well, here's the interesting point. When that rock arrives at the Earth, it will be moving SLOWER than the Earth in its orbit by 2500 m/sec. If it happens to swing up into the Earth's orbital path just ahead of the Earth, the Earth will run it down and smack right into it! And if it happens to swing up into the Earth's orbital path just behind the Earth, the Earth will be running away from it. Of course, the Earth's gravity will grab the trailing object and accelerate it down to the planet, BUT it will arrive with less than the Earth's escape velocity. That is highly unusual. If an object is standing still with respect to the Earth, it will land at escape velocity (ignoring that pesky atmosphere for a moment). If an object is moving toward the Earth, it will land at a speed greater than escape velocity, in many cases, MUCH greater than escape velocity (up to 72,300 m/sec for the fastest possible solar system object). For an object approaching on an interior orbit (like from Venus) it has in effect a negative approach velocity, making it possible for it to fall in at a speed no greater than 9200 m/sec. The SLOWER an object enters the atmosphere, the greater are its chances of surviving to become a meteorite in the hand. Entry speed is, in fact, the largest single factor determining survival. And what is true for Venus rocks is even more true for Mercury rocks. They can arrive at the Earth moving even more slowly and landing at an even lower speed. So, paradoxically, Earth-arriving meteorites originating from Venus and Mercury can be more favored for survival through the atmosphere than any other incoming object, like the conventional Asteroid Belt objects. And while I described the simplest direct orbit transfer from Venus to the Earth, any object that leaves Venus with an excess velocity of 2700 m/sec or greater, heading in any direction, will always cross the Earth's orbital sphere and, after perturbations from the solar plane, eventually cross the Earth's orbital plane and finally, sooner or later, it will do so when the Earth is there -- splat! In other words, if it doesn't hit anything else, it'll get here! Ditto for the Mercury rock. What's a hundred million years to a rock? So, where are those dozens and dozens of Venus meteorites? Sterling K. Webb __ Meteorite-list mailing list [EMAIL PROTECTED] http://www.pairlist.net/mailman/listinfo/meteorite-list
