[meteorite-list] addition to : quadrantids, 2003 EH1 & St. Marks meteorite

From: MexicoDoug_at_aol.com <MexicoDoug_at_meteoritecentral.com>
Date: Thu Apr 22 10:18:03 2004
Message-ID: <2117895F.2FCC415D.0BFED528_at_aol.com>

In a message dated 12/23/2003 5:08:43 AM Eastern Standard Time, marco.langbroek_at_wanadoo.nl writes:

> I enjoy this discussion with you, your suggestions are creative. I have
> given your new suggestions some thought, but I see two problems.

Lucky for me, you're Dutch, I assume. Last time I had the good fortune to be in Holland, everyone seemed so skilled to deal with such creativity, even when I was secretly just being stubborn. That wasn't this case, though.
 
> A large, compact fragment in an earth-crossing orbit similar to that of 2003
> EH1 with perihelion close to 1 AU (in essence: this is the Quadrantid stream
> orbit) would have a geocentric velocity of 40.2 km/s. That is very high for
> a meteorite surviving to be likely. Even a mass of several tons would likely
> completely disintegrate in an airburst.

OK, I can accept your premise. It would then, not be possible to tunnel through the Earth to South Africa, in the event of a reasonable incident angle, and then it still has to survive. Maybe it could skip off the atmosphere at the appropriate angle, but then, the only recorded fall seems to be below the horizon...OK.
 
> But what really rules out that St. Mark's is related to the Quadrantids &
> 2003 EH1, is that the Catalogue of Meteorites lists a fall time near 23:00
> local time. A fall from the direction of the 2003 EH1 orbit at this location
> at this time of the day is impossible, as the radiant is still far below the
> horizon. In fact, it barely rises for south Africa, attaining for the fall
> locality a maximum
> elevation of about 9 degrees only, at 8:40 local time. The radiant rises at
> 5:40 local time (nearly a quarter of a day after the reported time of fall
> of St. Marks) and sets at 11:45 local time, and a fall
> would only be possible within this time window.

Ouch. Six hours. I will take your word on the physics. So close but so far. The logic is good. I suppose at the velocity you predict would make a surviving impact less likely, but if at the highly improbably near horizontal entry angles through the atmosphere, we could have some air-braking and then arching, and plenty of material even falling beyond in the sea, south of the Cape. But I think you're right, it is time to give up. I also think we still need to see how those EH5 "parent" asteroids got to the Asteroid Belt...Orbits like 2003 EH1 might give some nice ideas. Also now I will be especially curious to learn more about the composition of 2003 EH1. You're very kind in working through my question. Good noon Europe, and here, bedtime.

Saludos, Doug
Received on Tue 23 Dec 2003 06:42:34 AM PST