In article ,
Harry wrote:

It is believed that in prehistoric times,
an ice comet collided with the
earth with so much force at a
spot near the Yucatan Peninsula,
that a chunk was dislodged and hurled
into orbit. This collected and compacted
becoming the earth`s moon.

I think you will find that the Earth had two moons, and the one in a
decaying orbit hit the Earth - creating the (now burried) crater, as well as
leavin us with a somewhat thinner crust. The bit of green cheeze out there,
over our heads, is as old as the "inner Earth", but like the Earth, it is
steadily growing as more space debris arrives.

As I understand it, the current "mainstream" thinking is that there
were numerous collision events, of greatly different magnitudes, and
very far apart in time.

It's now believed that quite early in the lifetime of the solar
system, when the planets were accreting out of a large dust-ring
around the young Sun, a planetoid of roughly the size of Mars collided
with the proto-Earth, striking a glancing blow. This impact shattered
the smaller body and did really serious damage to the larger (probably
re-melting much of it) and threw a lot of material back up into orbit
around the (now-larger) Earth. Much of this material eventually fell
back to the surface, some escaped entirely, and most of the rest
eventually formed the moon. This event occurred quite a few billions
of years ago.

The impact at what is now Chicxulub in the Yucatan was a lot more
recent (65 million years ago) and involved a much smaller body
(perhaps 10 miles across). Current mainstream thinking is that this
impact was probably the coup de grace for most of the dinosaurs... it
was one of the largest impacts in the history of Earth, but
there are geologic records of earlier impacts that left larger
craters (the Vredefort and Sudbury structures).

--
Dave Platt AE6EO
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