[meteorite-list] re: meteor velocities & Hoba

From: Marco Langbroek <marco.langbroek_at_meteoritecentral.com>
Date: Thu Apr 22 10:27:47 2004
Message-ID: <00c401c3a933$30bf3750$efc2ea3e_at_HAL>

Hello Jose and others

> I suppose that the Earth's gravitational attraction onto these =
> meteoroids would not account too much, on their slow, or very fast =
> relative velocities?

No, because it is the same for both 'slow' and 'fast' objects, so their
relative speed difference remains.

> On a slightly different matter: What would you think that, considering =
> its ~60 Ton mass, the great HOBA meteorite's entry velocity might have =
> attained on atmosphere entry?

Looking at the plots in Hills & Goda (Astron. J. 105, 1114) as a rough
indication, it should have been not more than 15 km/s. With larger
velocities it would have fragmented in smaller fragments.

> And why was it that most of it, did no =
> desintegrate to smaller fragments?
> Even at a lower minimum velocity of some 11 km/s, why is is that it did =
> not made a small hole/crater on the ground? (unless if its vestiges have =
> been eroded with time, bearing in mind it's estimated 80.000 yrs since =
> it fell to the ground).

This is a point about which I've wondered too! Looking at the plots in Hills
& Goda (Astron. J. 105, 1114), an iron body this size should actually be in
the range where it would retain some of its cosmic velocity (i.e. have
impact velocities of km/s, not m/s).

> Was it because of a very low =
> velocity? (which implies an asteroidal origin)

Being an iron meteorite, Hoba certainly is of asteroidal origin. Iron
meteorites are fragments of the metal cores of differentiated asteroids
(achondrites are the mantle materials of these).

- Marco

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Dr Marco Langbroek
Leiden, the Netherlands
52.15896 N, 4.48884 E (WGS 84)

meteorites_at_dmsweb.org
http://home.wanadoo.nl/marco.langbroek
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Received on Wed 12 Nov 2003 10:37:37 AM PST