Thanks for the relevant comments including:
>>Still I do not think this stream is a likely source of meteorites.
>>You point to the St. Mark's EH5, and Lost City H5 (which
>>anyhow has an orbit unlike that of 2003 EH1). St. Mark's is
>>a chondrite with a rather high petrologic grade (5), i.e. it has
>>undergone thermal metamorphism.� Those are not the kind of
>>bodies that I would connect with the clearly cometary
>>Quadrantid meteoroids.
Regarding St. Marks, first let me say that I believe the current main suspected source of EH5 -thermally altered- meteorite is believed to be in the asteroid belt between Jupiter and Mars. Perhaps you are right and it is not "cometary" in nature, but then, EH5 material doesn't belong in the asteroid belt either, where it is just as much out of place. A very eccentric earlier orbit would solve these problems.
Lost City was admittedly something that wasn't convincing, I mentioned it was simply to be complete, and between you and Elton's clue for verification, I retract it completely as a possibility, at least in my own mind.�
But: St. Marks (1877) is another story. As one may notice, the 2003 EH1 orbit before 1850 had a perihelion around 0.92 AU, and in the 1900's to date, around 1.19. Guess what year was the year its orbit (per JPL ephemeris, I assume reflecting the Jovian adjustments) was most close to 1.00 AU....Earth crossing? answer: just about 1877 !! Is it easy to check, for example in the St. Marks case, if a one ton "fragment" left the 2003 EH1 angular position, how close it would have to have been to us in the orbital gap to be captured (the radial position difference)? Here is where your having a better facility with the orbital mechanics calculation could be pretty convincing: How to capture a ton of inbound rock close to that orbit, at approximately the same orbital and velocity angle as the main mass (starting inbound at 0.75 AU from Earth on Dec 21, 1876) for a first approximation, but the closer to Earth, traveling at an Earth velocity component of about 31 km/s towards Earth, also corresponding to the moment when it is exposed to maximum acceleration since the close approach point is also its perihelion, solving for the magnitudes of closer radius or perturbation in velocity tangent vector necessary to pull the ton to impact here on Earth...keeping in mind that the main mass 2003 EH1 is at 0.52 AU by Jan 3-4 when the hypothetical ton smashes into the Earth.
To continue further alone this hypothesis regarding St. Marks (EH5 1877), I am quite reasonable agreeing with you that probability alone doesn't favor the conjecture that St Marks was a asteroid/cometary fragment from the orbit of the Quadrantids, and an especially large one at that, among the overwhelming typical particles.� What it does have going for it, though, is a fall date as Earth approaches the orbit (not recedes) of the meteoroids' distance in the Solar system plane.� As a matter of fact, the fall date of Jan 3, 1877 seems to have been slightly before the passage of the main mass 2003 EH1. It is noteworthy that it was inbound, too, which could even indicate a bit of gravitation acceleration, and furthermore while the main mass was inbound with respect to Earth at a major velocity (Main mass switched velocity direction to away with respect to earth on Jan 18, 1877 per JPL ephemeris precision), though the closest approach was Jan 4.
The "proof" (better said, the reason one is comfortable eliminating the possibility of St. Marks as part of the Quandrantids) I seem to understand as being the "cometary" nature of the asteroid or dead comet, 2003 EH1. Nevertheless, 2003 EH1 seems to be derived IN PART from the Quadrantids now assumed as being the parent body and non-penetrating particulate in nature.� What we do know is that there is a rock there, but we haven't seen its cometary tail in "life", nor its interior in "death", nor do we know where it was for its first 4.5 billion years.� Further, EH5 classifications were hypothesized possible to be derived from the Area of Venus' orbit.� I am way out on a limb here, but it is a good hypothesis I feel, since the heat grade alone isn't convincing at all to me...with the understanding that it is improbable, just like another improbability how quickly the particles seem to have uniformized.� Perhaps some measurements from the 2003 close approach (relatively close, 17th out of 138 in rank) gave data on whether 2003 EH1 contained water (St. Marks is anhydrous), or whether there exists a body of knowledge clearly excluding the EH5 meteorite composition as being derived from the dead asteroid-comet, which then nails your argument as true.
Thanks for entertaining the ideas, as there aren't many knowns here I'm enjoying very much exploring this issue, with someone like yourselfand this is the Meteorite interest list, so where else for me...; I have the most respect for your research into the subject.� If you have further information on the composition of the 2003 EH1 itself or especially vs. an EH5, please let me know.� Is it completely solid, for example?� Thanks again.
Saludos
Doug Dawn
Mexico
En un mensaje con fecha 12/22/2003 6:08:29 PM Mexico Standard Time, [EMAIL PROTECTED] escribe:
Asunto: [meteorite-list] re: Bootids (Quadrantids) meteor shower and 2003 EH1
Fecha: 12/22/2003 6:08:29 PM Mexico Standard Time
De: [EMAIL PROTECTED]
Para: [EMAIL PROTECTED]
CC: [EMAIL PROTECTED]
Enviado por Internet
>while the DUST distribution seems to have uniformized through
>the whole orbit in very short timing according to the paper and
>other sources, observers, etc., a disintegration event would likely
>still have any larger pieces nearer the main body, right?
Hello Dough,
That cannot be excluded of course. While called a "parent body", it is
equally valid to regard 2003 EH1 as just the biggest meteoroid in the
stream. Indeed, there could be fragments with sizes between the range ends
defined by 2003 EH1 and normal Quadrantid meteoroids. You are right in that.
Still I do not think this stream is a likely source of meteorites. You point
to the St. Mark's EH5, and Lost City H5 (which anyhow has an orbit unlike
that of 2003 EH1). St. Mark's is a chondrite with a rather
high petrologic grade (5), i.e. it has undergone thermal metamorphism.
Those are not the kind of bodies that I would connect with the clearly
cometary Quadrantid meteoroids.
Cheers,
- Marco
------
Marco Langbroek
Dutch Meteor Society (DMS)
Leiden, the Netherlands
52.15896 N, 4.48884 E (WGS 84)
[EMAIL PROTECTED]
http://home.wanadoo.nl/marco.langbroek
